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Group Title: Information circular - Florida Lakewatch, University of Florida ; 101
Title: Beginner's guide to water management: the abc's
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Title: Beginner's guide to water management: the abc's
Series Title: Information circular - Florida Lakewatch, University of Florida ; 101
Physical Description: Book
Language: English
Creator: Florida Lakewatch
Publisher: Gainesville, FL University of Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences
Publication Date: 1999
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Table of Contents
    Front Cover
        Front cover 1
        Front cover 2
    Prelude
        Page i
        Page ii
        Page iii
        Page iv
    Main
        Page 1
        Page 2
        Page 3
        Page 4
        Page 5
        Page 6
        Page 7
        Page 8
        Page 9
        Page 10
        Page 11
        Page 12
        Page 13
        Page 14
        Page 15
        Page 16
        Page 17
        Page 18
        Page 19
        Page 20
        Page 21
        Page 22
        Page 23
        Page 24
        Page 25
        Page 26
        Page 27
        Page 28
        Page 29
        Page 30
        Page 31
        Page 32
        Page 33
        Page 34
        Page 35
        Page 36
        Page 37
        Page 38
        Page 39
Full Text



A Beginner's Guide to

Water Management -The ABCs

Descriptions of Commonly Used Terms


Information Circular #101


Photo courtesy of UF/IFASES


.~ UNIVERSITY OF
" FLORIDA
Institute of Food and Agricultural Sciences


Florida LAKEWATCH
Department of Fisheries and Aquatic Sciences
Institute of Food and Agricultural Sciences
University of Florida
Gainesville, Florida
October 1999


LAKIWA-TH











A Beginner's Guide to

Water Management -The ABCs

Descriptions of Commonly Used Terms

Information Circular #101


ib. UNIVERSITY OF
FLORIDA
Institute of Food and Agricultural Sciences


Florida LAKEWATCH
Department of Fisheries and Aquatic Sciences
Institute of Food and Agricultural Sciences
University of Florida
Gainesville, Florida
October 1999


LAKAWH












Prologue

One of the goals of the Florida L.AKE\WATCH Program is to bridge the informa-
tion gap between the scientific community that studies Florida's \\aters and the people
w ho w-ant to learn about the lakes, rivers and streams they care for The first step
toward achieving this goal is to define a commonly understood language
Language is a funny thing Words can mean different things to different people
- even when they are speaking the same language From the lay public's view\point.
scientific terminology might as well be a foreign language Unfamiliar words may
con\ ey unintended meanings, or sometimes, no meaning at all Even the most
intelligent or w\ell-educated listeners cannot be expected to translate a specialized
scientific language \\-ithout a guide, especially when the language is not part of their
e\veryday experience
This document is the first in a series of Information Circulars the L.AKE\WATCH
Program is developing for the public It is an introduction to the basic terminology and
concepts used in the w-ater management arena Not all scientists and w-ater managers
may use the included terminology in precisely the same w-ay The descriptions used
here represent w-ater management as Florida L.AKEWVATCH professionals have come
to understand it


djrr~ ~









Sc~ ient4ifi [Mek~[4thod


W hen faced with the task of explaining how
things work in the physical world, scientists
developed an investigative
process called the "scientific
method." This system has been
used for centuries and contin- ...
ues to be used today.
Ideally, the scientific
method proceeds in stages.
First, observations are made.
These are considered to be .
"facts." Then suppositions,
called "hypotheses," are made
that seem to explain the cause-
and-effect relationship among ;' S
the facts. A hypothesis is a r
highly tentative statement a .
hunch about how things work.
Next, experiments are performed
to test whether a hypothesis can -- -. '
correctly account for the
experimental results that are
observed.
During this stage, measurements called "data"
are taken. If the data are consistent with the predic-
tions made using the hypothesis, the hypothesis gains
credibility. If not, then the hypothesis is either
discarded or modified. A hypothesis often goes
through many revisions. After repeated experimental
verifications, a hypothesis becomes a "theory." The
distinction between a hypothesis and a theory has
become blurred in recent years.
A theory is not a tentative statement like a
hypothesis a theory has a high probability of
being correct. For a theory to become accepted by
the scientific community, there must be a consensus
in the scientific community that a theory represents
the truth.
The lay person should bear in mind that even
though a scientific theory is believed to be credible
by the scientific community, it could still be wrong.


Widely accepted theories are difficult to challenge,
so they often persist. Scientists have been known to
develop parental, protective
attitudes toward their theories,
sometimes defending them
S.. with a zeal that is far from
.... objective.' And challengers
S" ." face skepticism, even derision,
Which has often brought tragic
*^ r' personal consequences. The
history of science is replete
with examples.
For instance, Nobel Prizes
have even been awarded to
scientists who have had the
courage and vision to contest
popular theories in favor of
,t new, more accurate ones.
r. Usingthe scientificmethod
S can require many years of
Gathering and evaluating
i evidence, formulating and
reformulating hypotheses, and
debating the value of competing theories and even
after all that, an accepted theory may eventually be
proven false.
Unfortunately, developing reliable theories in
the water management arena may take years, even
centuries. In the meantime, understanding the specu-
lative nature of the scientific method is important for
both the lay public and professionals. Before anyone
accepts a theory or a hypothesis, he or she should
always find out what evidence supports it and whether
there is any evidence that contradicts it.
In this way, hypotheses and widely-accepted
theories can be put into proper perspective. Any
hypothesis or theory is only as valid as the evaluative
thought process that has produced it.

1 Refer to Chamberlin 's article "The Method of Multiple
Working Hypotheses" (see references at the end of this
circular).














To apply the scientific method properly, experi-
ments must be performed during which measure-
ments must be made. Every measurement consists
of two parts: a number (how much?) and a unit of
measure (i.e., pound, foot, second, etc.). For example,
in the measurement "5.2 hours," the "5.2" tells how
much, and "hours" is the unit of measure.
There are two primary systems used for mak-
ing measurements, the metric system and the English
system. The United States is attempting to convert to
the metric system, but acceptance by the general pub-
lic has been slow. Because most scientific studies
(including Florida LAKEWATCH research) utilize


the metric system, it will be used in this document. If
you want to put a measurement into more familiar
terms, you can calculate its English equivalent.
Though converting is not necessary, it's helpful when
you are trying to visualize quantities.
The following table shows common metric units
and the conversion factors that can be used to calcu-
late their equivalents in the corresponding English units.
To convert a metric unit to an English unit, multiply
the metric measurement by the conversion factor shown
in the table. For example, multiply 5 meters times the
conversion factor of 3.281 to get 16.405 feet 5
meters and 16.405 feet are the same distance.


Metric Unit Conversion Factor English Unit

centimeter (cm) 0.3937 inch (in)

meter (m) 3.281 feet (ft)

kilometer (km) 0.6214 mile (mi)

square kilometer (km2) 0.3861 square mile (mi2)

hectare (ha) 2.471 acre (ac)

kilogram (kg) 2.205 pound (lb)

Liter (L or 1) 1.057 U.S. quart (qt)

cubic meter (m3) 264 U.S. gallon (gal)

milligrams/Liter (mg/L) 1.0 parts/million (ppm)

micrograms/Liter (pg/L) 1.0 parts/billion (ppb)

Celsius (C) (C x 9/5) +32 Fahrenheit (F)


Metric to English Conversion Factors














Converting from one unit of measure to another
within the metric system is much easier than converting
within the English system. The table below shows
the most common conversion factors.


When you have an Multiply by To get the equivalent
amount in these units: this number: in the units below:

milligrams (mg) 1000 micrograms (jag)


grams (g) 1000 milligrams (mg)

kilograms (kg) 1000 grams (g)

cubic meters (m3) 1000 liters (L or 1)


microgram per Liter (pLg/L) 1 milligram per cubic meter (mg/m3)


Note that the value of each metric conversion factor is indicated by the
prefixes used:

> milli means "one-thousandth,"
> micro means "one-millionth", and
> kilo means "one thousand."


Metric Units
















Suggestions: The descriptions in this document will make more sense to you
if you start by:
1) becoming familiar with the Measurement Units described on pages iii and iv so that
metric units are not distracting to you when you encounter them in the text; and
2) reading the entries for Algae, Aquatic Macrophytes, Biological Productivity, and
Trophic State. These particular entries will provide a background in the basic, often-
used vocabulary and concepts.

Note: the c- symbol will be used to refer you to other relevant
entries in this circular.


Algae
are a wide variety of tiny,
often microscopic, plants
(or plant-like organisms)
that live both in water and
on land. The word "algae"
is plural (pronounced AL-
jee), and algaa" is the
singular form (pronounced
AL-gah). Pedlastrum
One common way to classify water-dwelling
algae is based on where they live. Using this
system, three types of algae are commonly
defined as follows:
+ phytoplankton float freely in the water;
+ periphyton are attached to aquatic vegetation
or other structures; and
+ benthic algae grow on the bottom or bottom
sediments.

cr See Benthic, Periphyton, and
Phytoplankton.


Algae may further be described as being
colonial which means they group together in
colonies, or as being filamentous which means
they form hair-like strands. The most common
forms of algae are also described by their colors:
green, blue-green, red, and yellow. All these
classifications may be used together. For
example, to describe blue-green, hair-like algae
that are attached to an underwater rock, you
could refer to them as "blue-green filamentous
periphyton."
In addition to describing types of algae, it is
useful to measure quantity. The amount of algae
in a waterbody is often called algal biomass.
Scientists commonly make estimates of algal
biomass based on two types of measurements:
+ Because almost all algae contain chlorophyll
(the green pigment found in plants), the concen-
tration of chlorophyll in a water sample can be
used to indicate the amount of algae present. This
method, however, does not include all types of
algae, only the phytoplankton. Chlorophyll
concentrations are measured in units of "micrograms
per Liter" (abbreviated "pg/L") or in "milligrams per
cubic meter" (abbreviated "mg/m3").








+ In certain cases scientists prefer to count the
individual algal organisms in a sample and use their
count to calculate the weight of the algae.

" ,,\e C'hn-orohyll


Some people consider algae to be unsightly,
particularly when it is abundant. For instance, a
phytoplankton bloom can make water appear so
green that it's described as "pea soup."
In Florida when chlorophyll concentrations
reach a level over 40 pg/L, some scientists will
call it an "algae bloom" or "algal bloom." The
public, however, usually has a less scientific
approach. They often define an algal bloom as
whenever more algae can be seen in the water
than they are accustomed to seeing (even though
this may be a low concentration in some cases).


Algal blooms _
may be caused .,.. '
by human "'
activities, or .
they may be Mycrocysti euglenoid
naturally
occurring. Sometimes, what seems to be an algal
bloom is merely the result of wind blowing the
algae into a cove or onto a downwind shore,
concentrating it in a relatively small area, called
"windrowing."
The Role of Algae in Waterbodies:
Algae are essential to aquatic systems. As a vital
part of the food web, algae provide the food necessary
to support all aquatic animal life. Certain types of
algae also provide habitat for aquatic organisms. On
occasion, however, they can become troublesome


and several examples are described as follows:
+ An algal bloom can block sunlight, preventing
the light from reaching the submersed aquatic
plants below.
+ Periphyton filamentouss algae) blooms and
benthic algal blooms have the potential to interfere
with other recreational uses like boating and fishing.
+ An algal bloom can trigger a fish kill. In Florida
this is most likely to occur after several days of hot
weather with overcast skies.

e .\'e Fish Kill.

Health Concerns:
Newspapers and magazines often present ar-
ticles describing toxic algae. However, most algae
are not toxic and pose very little danger to humans.
It should be remembered that toxic algae can be
found in all aquatic environments.
Known health problems associated with
algae have generally been associated with high con-
centrations of three species of blue-green algae -
Anabaenaflos-aquae, Microcystis aeruginosa, and
Aphanizomenon flos-aquae. With few exceptions,
only fish and invertebrates have died from the
effects of these toxic algae.
In Florida, it's believed that it is extremely
rare for algae to cause human illness or death.
People are more likely to suffer minor symptoms
such as itching. Several species of algae produce
gases that have annoying or offensive odors, often
a musty smell. These odiferous gases may cause
health problems for some individuals who have
breathing difficulties.
To be prudent, people should inform their
doctor if they live near a waterbody or use a
waterbody often. This is critically important at
this time because there is an alga called
Pfiesteria that is known to cause severe health
problems.
If it is present, Pfiesteria tends to be found
primarily in tidal waters. It, however, must be
recognized that people will face a greater risk
during their drive from home to the grocery store
than from Pfiesteria or any other toxic algae.
Prudence must be the watchword when using any
waterbody.








Algae Bloom
(orAlgal Bloom)
In Florida, when chlo-
rophyll concentrations
reach a level over 40 pg/L,
some scientists will call
it an "algae bloom" or
"algal bloom."
Photo by Chuck Cichr
e See Algae.


Algal Biomass
is the amount of algae in a waterbody at a given
time. In this document, all estimates of the
amount of algal biomass in a waterbody will be
based on chlorophyll measurements.

e See Algae.


Alkalinity
refers to water's ability, or inability, to neutralize
acids. The terms "Alkalinity" and "Total Alkalin-
ity" are often used to define the same thing.

c- See Total Alkalinity.



Aquatic Macrophytes
are aquatic plants that are large enough to be
apparent to the naked eye; in other words, they are
larger than microscopic aquatic plants. The general
term "aquatic plants" usually refers to aquatic
macrophytes, but some scientists use it to mean
aquatic macrophytes and algae.
Aquatic macrophytes characteristically
grow in water or in wet areas and are quite a
diverse group. For example, some are rooted in
the bottom sediments, while others float on the
water's surface and are not rooted to the bottom.
Aquatic plants may be native to an area, or they
may have been imported (referred to as "exotic").
Some aquatic macrophytes are vascular
plants, meaning they contain a system of fluid-
conducting tubes, much like human blood


vessels. Cattails, waterlilies, and hydrilla are
examples. Large algae such as Cladophora,
Lyngbya, and Chara are also included in the
category of aquatic macrophytes.

* See Emtergent Plants. Floating-leaved
Plhtn,. ,tl /.1niblshiiereld Plants.

Even though they are quite diverse, aquatic
macrophytes have been grouped into three general
categories:
+ emergent aquatic plants are rooted in the
bottom sediments and protrude up above the
water's surface;
+ submersed aquatic plants primarily grow
completely below the water's surface; and
+ floating-leaved aquatic plants can be rooted to
the waterbody's bottom sediments and also have
leaves that float on the water's surface.


In the eye of the beholder...
An aquatic weed problem is often
defined differently by people who use a
waterbody in different ways. For
instance, for an angler a weed problem
may be where aquatic macrophytes
block boat access and snag fishing
lines. However, for an industry man-
ager, it may be where aquatic macro-
phytes clog cooling-water intakes or
interfere with commercial navigation








Aquatic macrophytes are a natural part of
waterbodies, although in some circumstances they
can be troublesome. The same plant may be a
"desirable aquatic plant" in one location and a
"nuisance weed" in another. When exotic aquatic
plants have no natural enemies in their adopted
area, they can grow unchecked and may become
overly abundant.
In Florida for example, millions of dollars
are spent each year to control two particularly
aggressive and fast-growing aquatic macrophytes
- water hyacinth, an exotic aquatic plant that is
thought to be from Central and South America,
and hydrilla, an exotic aquatic plant that is
thought to be from Africa. The term "weed" is
not reserved for exotic aquatic plants, in some
circumstances, our native aquatic plants can
cause serious problems, too.
When assessing the abundance of aquatic
plants in a waterbody, scientists may choose to
measure or calculate one or more of the following:
+ PVI (Percent Volume Infested or Percent Volume
Inhabited) is a measure of the percentage of a
waterbody's volume that contains aquatic plants;
+ PAC (Percent Area Covered) is a measure of the
percentage of a waterbody's bottom area that has
aquatic plants growing on or over it;
+ frequency of occurrence is an estimate of the
abundance of specific aquatic plants; and
+ average plant biomass is the average weight of
several samples of fresh, live aquatic plants grow-
ing in one square meter of a lake's area.

r .\'e .Average Plant Biomnass. Frequency(
of (kOccrrIence. PI l. nd P-IC.


The Role of Aquatic Macrophytes in
Waterbodies:
Aquatic macrophytes perform several
functions in waterbodies, often quite complex
ones. A few are briefly described below.
+ Aquatic macrophytes provide habitat for fish,
wildlife, and other aquatic animals.
+ Aquatic macrophytes provide habitat and food
for organisms that fish and wildlife feed on.


An unexpected
result....
During their
lifetime, aquatic
plants slough off
dead leaves and
other plant parts
that sink to the
bottom In this
wa\y, the\, contribute continually to the
formation of sediments A study of water
hyacinths has shox n that amount of
sediment they contributed when a herbi-
cide w\as used to kill them all at once w\as
less than it W\ould have been if the plants
had been allowed to live out their full
lifetimes


* Aquatic macrophytes along a shoreline can protect
the land from erosion caused by waves and wind.
+ Aquatic macrophytes can stabilize bottom
sediments by dampening the wave action.
+ The mixing of air into the water that takes place
at the water's surface can be obstructed by the
presence of floating plants and floating-leaved
plants. In this way, they can cause lower oxygen
levels in the water.
+ Floating plants and floating-leaved plants create
shaded areas that can cause the growth of
submersed plants beneath them to be slowed.
+ When submersed aquatic plants become more
abundant, these plants can cause water to become
clearer. Conversely, the removal or decline of large
amounts of submersed aquatic plants can cause
water to become less clear.
+ When aquatic macrophytes die, the underwater
decay process uses oxygen from the water which
can become severely oxygen-poor if massive
amounts of plants die simultaneously.
+ Decayed plant debris (dead leaves, etc.) contrib-
utes to the buildup of sediments on the bottom.

4" ee.- lgae. Fish Kill. and If iter Clarir.








Aquatic Plant

ce See Aquatic Macrophytes and Algae.


Average Plant Biomass
(as measured by Florida LAKEWATCH) is the
average weight of several samples of fresh, live
aquatic plants growing in one square meter of a
lake's area. This measurement is done separately
for each category of plants: submersed, floating-
leaved, and emersed. Measurements of average
plant biomass are commonly used to help assess a
waterbody's overall biological productivity and to
assess the abundance of the different categories of
aquatic plants present in a waterbody.

" .\,e biological Productivity.

When Florida LAKEWATCH staff measures
aquatic plant biomass, they use the following procedure:
* Between 10 and 30 evenly-spaced sampling
locations are chosen around the waterbody;
* At each sampling location, sampling is performed
in three sites one in the emergent plant zone,
another in the submersed plant zone, and a third in
the floating-leaved plant zone;
* At each site, a square frame (one-quarter of a
square meter in area) is tossed into the water;
* All above-ground aquatic plant material in the
water column that falls inside the frame is harvested;
* The harvested plants are whirled around in a net
bag to spin off excess water;
* The plants are then weighed on a scale that
measures kilograms or grams;
* To calculate the biomass that would be in one
square meter, the weight is multiplied times 4; and
* The values from all the sites for each category of
aquatic plants are averaged separately.
The recorded weights are called wet weight,
because the plants are not allowed to dry out internally,
like dried flowers. Plant biomass is also referred to as
fresh plant weight and is reported by Florida
LAKEWATCH in units of "kilograms wet weight per
square meter" (abbreviated "kg wet wt/m2").


Emergent
plants are
being
collected
here (right)
to calculate
Average
Plant
Biomass.


P n


Submersed plants (above)
andjl,i,, g-i, ,. In../ plants
(left) are collected and
then spun to shake off
excess water before being
weighed.


Photos byAmyRihard







Some professionals will use plants they have
allowed to dry internally. Also, many professionals
include the weight of plant roots in their measure-
ment of biomass. Florida LAKEWATCH only uses
the wet weight of above-ground plant biomass
because no expensive equipment is required and the
results are just as useful for LAKEWATCH purposes.

Benthic
is an adjective indicating something is relating to
or occurring in the bottom sediments in a
waterbody.

Benthic Algae
are algae that grow on the bottom sediments of a
waterbody. Benthic algae are most commonly
filamentous or colonial forms, but also may be
microscopic single-celled organisms.
Benthic algae perform various beneficial
functions in waterbodies, but may also be trouble-
some. Several examples of problems associated
with benthic algae are described below:
+ Benthic algal growths can snag anglers' fishing gear.
+ Dense benthic growths can break free of the
bottom and float to the surface.
+ Large rafts of free-floating algae may form obstruc-
tive mats that can accumulate along shorelines.
+ Offensive odors can be produced when benthic
algae mats decompose.

e See Algae.

The Role of Benthic Algae in Waterbodies:
Benthic algae provide food and habitat for
many aquatic organisms. In this way they con-
tribute to the biological productivity of aquatic
systems.

e See Biological Productivity.

Health Concerns:
Benthic algae generally do not pose a
known direct threat to human health in water-
bodies.


Biological Productivity
is defined conceptually as the ability ofa waterbody to
support life (such as plants, fish, and wildlife). Biologi-
cal productivity is defined scientifically as the rate at
which organic matter is produced. Measuring this rate
directly for an entire waterbody is difficult and
prohibitively expensive by most standards.
For this reason, many scientists base estimates
of biological productivity on one or more quantities
that are more readily measured. These include
measurements of concentrations of nutrients in
water, concentrations of chlorophyll in the water,
aquatic plant abundance, and/or water clarity. The
level of biological productivity in a waterbody is
used to determine its trophic state classification.

r See Aquatic Plants, Chlorophyll,
Nutrients, Trophic State, and Water Clarity.


Biomass
is the amount of living matter (as in a unit area
or volume of habitat).

r See Algae and Average Plant Biomass.


Calcium
is a mineral that dissolves easily in water. The
chemical symbol for calcium is "Ca." It is one of
the most abundant substances in surface waters and
ground waters.
Freshwaters around the world have higher
concentrations of calcium when they are located
closer to calcium-rich soils and rocks. Typical calcium
concentrations worldwide are less than 15 mg/L, but
waters close to calcium-rich carbonate rocks often
have calcium concentrations exceeding 30 mg/L.
Calcium enters the aquatic environment prima-
rily through the weathering of rocks like limestone,
which is largely composed of calcium compounds. In
some circumstances, calcium can also be deposited in
waterbodies as a result of human activities, often
because of the extensive use of calcium-containing
chemicals in agriculture and industry.
Having calcium in your water supply may
cause inconveniences. For example, you may have








high concentrations of chloride, because they are close
to marine (i.e., saltwater) systems. In these waterbodies,
seawater can seep underground, called saltwater
intrusion, or flow directly into them through tidal flow,
for instance. Also, sea spray carries chloride into the air
where it can then enter waterbodies as part of rainfall,
even far from coastal areas.
The saltiness, or chloride concentration, of
water can affect plants and wildlife. For example,
some species die in water that is too salty, and
others die in water that is not salty enough.
In Florida:
Waterbodies in the Florida LAKEWATCH
database analyzed prior to January 1998, had
average chloride concentrations which ranged from
1.7 to 2300 mg/L. Over 75% of these waterbodies
had chloride concentrations less than 22 mg/L.
Health Concerns:
Chloride concentrations in lakes are generally
so low that they pose no known threat to human
health. Water will have a strong salty taste if
chloride concentrations exceed 250 mg/L.
It should be noted that although the chlorides are
not dangerous themselves, they signal the possibility
of contamination from human or animal wastes that
can contain bacteria and other harmful substances. For
this reason, it is prudent to investigate where the
chlorides are coming from when high concentrations
are detected in an inland waterbody.

Chlorophyll
is the green pigment
found in plants and
found abundantly in
nearly all algae. Chloro-
phyll allows plants and
algae to use sunlight in LAKEWATCH ..... lake
the process of photo- water ,'. ,. i TCHLsamples.
synthesis for growth. Thanks to chlorophyll, plants
are able to provide food and oxygen for the
majority of animal life on earth.
Scientists may refer to chlorophyll a, which
is one type of chlorophyll, as are chlorophyll b and
chlorophyll c. Measurements of total chlorophyll
include all types. Chlorophyll can be abbreviated
"CHL," and total chlorophyll can be abbreviated
"TCHL."


The Role of Chlorophyll in Waterbodies:
Measurements of the chlorophyll concentra-
tions in water samples are very useful to scientists.
For example, they are often used to estimate algal
biomass in a waterbody and to assess a waterbody's
biological productivity.

c See Algae, Algal Biomass, Biological
Productivity, and Phytoplankton.

In Florida:
Waterbodies in the Florida LAKEWATCH
database analyzed prior to January 1998, had
average chlorophyll concentrations which ranged
from less than 1 to over 400 pg/L. Using these
average chlorophyll concentrations from this
same database, Florida lakes were found to be
distributed into the four trophic states as follows:2
+ 12% of these lakes (those with chlorophyll values
less than 3 pLg/L) would be classified as oligotrophic;
+ about 31% of these lakes (those with chlorophyll
values between 4 and 7 jtg/L) would be classified
as mesotrophic;
+ 41% of these lakes (those with chlorophyll
values between 8 and 40 jtg/L) would be classified
as eutrophic; and
+ nearly 16% of these lakes (those with
chlorophyll values greater than 40 pLg/L) would be
classified as hypereutrophic.

.We TropIhic Satae t i',l 1/ e ,/, .I//.
i '.-i, ,rice Olgotrnvhic. .lles.otrophic,
Eutroplhic, alnd Hipereutrophic

S In Florida, characteristics of a lake's
geographic region can provide insight into how
much chlorophyll may be expected for lakes in
that area. For example, water entering the water-
bodies by stream flow or underground flowage
through fertile soils can pick up nutrients that
can then fertilize the growth of algae and aquatic
plants. In this way, the geology and physiogra-
phy of a watershed can influence a waterbody's
biological productivity significantly.

See Lake Region.


2 This distribution oftrophic state is based solely -i i. o. 'p,,' values without utiliing information on nutrient concentrations or water clarity.







Health Concerns:
Chlorophyll poses no known direct threat to
human health. There are some rare cases where
algae can become toxic in high enough abun-
dance to cause concern. However, toxic algae are
generally not a problem.

e See Algae.


Color
in waterbodies has two ~ -
components:
(1)the"apparent" color
which is the color of a
water sample that has
not had the particulates
filtered out of the wa-
ter; and
(2) the "true" color,
which is the color of a
water sample that has Photo by MltPuam, UF/IFASEMS
water sample that has
had all the particulates filtered out of the water
The measurement of true color is the one most
commonly used by scientists. To measure true color, the
color of the filtered water sample is matched to one
from a spectrum of standard colors. Each of the
standard colors has been assigned a number on a scale
of "platinum-cobalt units" (abbreviated as either "PCU"
or "Pt-Co units"). On the PCU scale, a higher value of
true color represents water that is more darkly colored.
The Role of Color in Waterbodies:
Dissolved organic materials, such as humic acids
from decaying leaves, and dissolved minerals can give
water a reddish brown color which makes it look like tea.
The presence of color can reduce both the
quantity and the quality of light penetration into the
water column. As a result, high color concentra-
tions (greater than 50 PCU) may limit the amount
and types of algae that can grow in a waterbody.
Changing the quantity and quality of light reaching
the bottom of a waterbody can also influence the
depth of colonization and the types of aquatic
plants that can grow there. In some waterbodies,
color is the "limiting" environmental factor.

- See Humic Acids, Limiting Environmental
Factor, and Water Clarity.


In Florida:
Waterbodies in the Florida LAKEWATCH
database analyzed prior to January 1998, had
average color values which ranged from 0 to over
700 PCU. Over 75% of these waterbodies had
color values less than 70 PCU.
Waterbodies that adjoin poorly drained areas
(such as swamps) often have darker water, espe-
cially after a rainfall. Consequently, the location of
a waterbody has a strong influence on its color. For
example, lakes in the well-drained New Hope
Ridge/Greenhead Slope lake region in northwest-
ern Florida (in Washington, Bay, Calhoun, and
Jackson Counties) tend to have color values below
10 PCU. While lakes in the poorly-drained
Okefenokee Plains lake region in north Florida (in
Baker, Columbia, and Hamilton Counties) tend to
have values above 100 PCU.

- See Lake Region.

Health Concerns:
There is no known direct health hazard of
color. Consequently, the level of color that is
acceptable depends on personal preference. Water
transparency, however, may be reduced in highly
colored waters (greater than 50 PCU) to the point
where underwater hazards may be concealed,
creating a potentially dangerous situation for
swimmers, skiers, and boaters.

Common
Plant Name -
Plants have "scientific" names -
and "common" names. For
example, the floating aquatic
plant known scientifically as
Nuphar luteum is also known Nuhar luteum also
by its common name "cow known as "cow lily"
lily" or spatterdockk." The or spatterdockk."
common name of a plant
may vary from place to place, and the same com-
mon name may even be used for different plants.


e See Plant Species and Scientific
Plant Name.








Conductance (or Conductivity)

c See Specific Conductance.


Emergent
Plants d-
are aquatic plants that
are rooted in the
bottom sediments and
protrude up above the
water's surface. Annual Spkerush (Eleochars geniculata)
UF/IFAS CenterforAquatic and Invasve Plants
Cattail, maidencane,
and bulrush are examples of emergent plants.
Emergent plants grow in water-saturated soils and
submersed soils near the edge of a waterbody.
They generally grow out to a maximum depth of
from 1 to 3 meters (from about 3 to 10 feet).
Emergent plants perform many functions in
waterbodies. A few are described below:
* Emergent plants provide habitat for fish.
* Emergent plants provide food and habitat for
wildlife populations such as ducks.
* Emergent plants reduce shoreline erosion.
* Emergent plants increase evapotranspirational3
water losses from a waterbody, sometimes to the
point where water levels are lowered.
* Emergent plants shed leaves and other plant
debris, adding to the bottom sediments and making
the water shallower.
* As emergent plant debris accumulates in shallow
water areas, shorelines migrate lakeward.
* Uprooted plants can form floating islands called
"tussocks" that can be significant navigational
hazards and block access to parts of the waterbody
It should be noted tussocks also provide bird and
wildlife habitat.
Emergent plants react in various ways to
changing water levels. When periods of low water
are followed by a rapid rise in water level, large


3Evapotranspiration is ,. ,' evaporation. Evapotranspiration
is the process in which water evaporates from the surface ofplants or is
emitted as a vapor from the surface of leaves or other plant parts.


sections of emergent plants may be uprooted.
Sustained high water can also reduce emergent
plant abundance. In periods of low water, debris
from emergent plants is a significant factor.
Accumulated plant debris can eventually (i.e.,
100-10,000 years) cause the lake to become
more shallow, eventually forming a swamp or
marsh, and ultimately, peat deposits.

Sc- See Aquatic Macrophytes, Emergent
Plant Biomass and Width of Emergent
and Floating-leaved Zone.

In Florida:
Emergent plants occur naturally in all Florida
waterbodies. The width of the emergent zone (from
the shoreline out into the lake) may vary from a
few meters to hundreds of meters. Its size changes
most often in response to changing water levels. If
the emergent plants have been allowed to grow
without human intervention, the lakeward edge of
the emergent plants can be used to show where a
waterbody's low water level has been in the past
few years or perhaps even decades.
Health Concerns:
Emergent plants are not generally thought
of as a cause of human health problems. How-
ever, dense growths of emergent plants provide
habitat that can harbor disease-carrying
mosquitoes.

Emergent Plant Biomass
(as used by Florida LAKEWATCH) is the aver-
age weight of fresh, live emergent aquatic plants
growing in one square meter of a lake's bottom
area. The measurement of average emergent
plant biomass in a waterbody is one of several
measurements that can be used to assess a
waterbody's overall biological productivity.

c See Average Plant Biomass
and Biological Productivity.

In Florida:
Average emergent plant biomass in Florida
lakes generally ranges from 0 to 27 kg wet wt/m2.
Emergent plant biomass appears to be linked with a








waterbody's biological productivity. For example:
* in biologically less productive lakes (oligotrophic
lakes), the average emergent plant biomass is about
2.5 kg wet wt/m2;
* in moderately productive lakes (mesotrophic
lakes), the average emergent plant biomass is about
3.0 kg wet wt/m2;
* in highly productive lakes (eutrophic lakes), the
average emergent plant biomass is about 3.5 kg wet
wt/m2; and
* in the most highly productive lakes (hypereutrophic
lakes), the average emergent plant biomass is about
4.0 kg wet wt/m2.

r See Trophic State and each ofits categories:
Oligotrophic, Mesotrophic, Eutrophic, and
Hypereutrophic.


Photo byMark Hoyer
Eutrophic
is an adjective used to describe the level of biologi-
cal productivity of a waterbody. Florida LAKE-
WATCH and many professionals classify levels of
biological productivity using four trophic state
categories (oligotrophic, mesotrophic, eutrophic,
and hypereutrophic). Of the four trophic state
categories, the eutrophic state is defined as having a
high level of biological productivity, second only to
the hypereutrophic category. The prefix "eu" means
good or sufficient.
A eutrophic waterbody is capable of producing
and supporting an abundance of living organisms
(plants, fish, and wildlife). Eutrophic waterbodies
generally have the characteristics described below:
+ Eutrophic lakes are more biologically productive


than oligotrophic and mesotrophic lakes and are often
some of Florida's best fishing lakes. They usually
support large populations offish, including sportfish
such as largemouth bass, speckled perch, and bream.
* Typically, eutrophic waters are characterized as
having sufficient nutrient concentrations to support
the abundant growth of algae and/or aquatic plants.
* When algae dominate a eutrophic waterbody, its
water will have high chlorophyll concentrations
(greater than 7 Lg/L). The result will be less clear
water, causing Secchi depth readings to be low. In
contrast, when instead of algae, aquatic plants
dominate a eutrophic waterbody, its water will have
lower chlorophyll concentrations and often lower
nutrient concentrations and clearer water. The
resulting water clarity will be reflected in Secchi
depth readings that are greater than in eutrophic
waterbodies that have low levels of aquatic plants.
Despite being classified as eutrophic, these
plant-dominated waterbodies display the clear
water, low chlorophyll concentrations, and low
nutrient concentrations that are more characteristic
of mesotrophic or oligotrophic waterbodies.
* Regardless of whether eutrophic waterbodies are
plant-dominated or algae-dominated, they gener-
ally have a layer of sediment on the bottom result-
ing from the long-term accumulation of plant
debris. In some eutrophic lakes, however, the
action of wind and waves can create beaches or
sandy-bottom areas in localized places.
* Eutrophic waterbodies can have occasional algal
blooms and fish kills. However, fish kills generally
occur in hypereutrophic lakes when chlorophyll
concentrations exceed 100 lgg/L.

c See Algae, Aquatic Macrophytes,
Chlorophyll, Fish Kill, Hypereutrophic,
Mesotrophic, Oligotrophic, Secchi Depth,
Trophic State, and Water Clarity.


Fish Kill
is an event in which dead fish are observed. Some fish
kills are extremely noticeable and may be viewed by
the public as being damaging to the fish population.
However, contrary to their appearance, typical fish
kills in lakes only affect a small percentage of the fish








in a waterbody. Fish kills may occur for several reasons.
The most common cause offish kills is related
to the depletion of oxygen in shallow waterbodies.
Oxygen depletion may be caused in various ways.
Three of the most common are as follows:
SWhenever aquatic organisms die, oxygen is pulled
from the water column and is used in the decay
process. Oxygen can become critically reduced in this
way, especially in waterbodies that have an abundance
of algae. For waterbodies in which the concentration of
total chlorophyll exceeds 100 gg/L (indicating a high
algae level), oxygen depletion is a likely cause of a fish
kill. This is because the fraction of the algal population
that is dying naturally is a large amount of mass; and
therefore, its decomposition can consume significant
amounts of oxygen.

SSimilarly, oxygen depletion can also occur
when large amounts of aquatic plants die within
a short time. Herbicide applicators commonly treat
areas of aquatic plants at different times in order to
avoid this situation, or they use herbicides that
cause plants to die slowly.
3 A fish kill due to oxygen depletion can also be
triggered by several days of overcast skies,
especially during hot weather. This can happen
because aquatic plants and algae add oxygen to water
only when there is sufficient sunlight for photosynthe-
sis; however, they consume oxygen all the time in
their normal biological processes. When overcast
skies persist for several days, oxygen levels can
become depleted, because the plants are using more
oxygen than they are producing. Waters are particu-
larly vulnerable when the temperature is high, because
warmer water contains less oxygen to start with than
cooler water does. A symptom of oxygen depletion is
when the fish are "gulping" at the surface.
Some species offish die naturally in large
numbers after spawning or when they are stressed by
unusual or harsh weather conditions. High concen-
trations of hydrogen sulfide (perhaps from a sulfur-
water spring or artesian well) may be the cause of a
fish kill. In this case, sometimes a smell like rotten
eggs is noticeable.

i .i'e .-/lue. Entoriihic. HyliereItitriphic.
.Sl/fiur. ,d11 Total C'h/ro phill.


Floating-
leaved
Plants


are aquatic plants that are '
primarily rooted to the i "
waterbody's bottom l 1-
Water shield (Brasema schreben)
sediments and also have
leaves that float on the water's surface.
Waterlilies, bonnets, spatterdock, and lotus
are examples of floating-leaved plants. Although
usually not rooted on the bottom, water hyacinth
and water lettuce are also included in this plant
classification. Floating-leaved plants are generally
found growing along the shoreline, lakeward of
the emergent plants. Floating-leaved plants
perform many functions in waterbodies. Some of
the most common are described below:
+ According to many aquatic scientists, the
primary role of floating-leaved plants in waterbod-
ies is to provide food and habitat for wildlife and
fish. Food for fish is provided principally when
many varieties of small animals feed on the algae
that have attached themselves to the plants.
+ Floating-leaved plants can reduce shoreline erosion.
+ The decaying material floating-leaved plants
produce over many years (i.e., 100-10,000 years)
accumulates in the sediments, playing an influential
role in making a waterbody shallower.
+ Debris from floating-leaved plants contributes to
the formation of peat deposits, particularly as the
lake becomes more shallow over time and aquatic
plants grow more abundantly.
+ If periods of low water are followed by a rapid rise
in water level, the roots of dead floating-leaved plants
(called rhizomes) can float to the surface where they
block access and cause difficulties with navigation.
+ In many cases, masses of rhizomes uprooted from
the bottom can form floating islands called "tussocks."
Tussocks can become so large that trees can grow on
them.
+ In waterbodies where water hyacinths or water
lettuce grow extremely well, these plants may
completely cover the waterbody's surface and
cause major navigational problems.


1s
i
a-
4.


V.,








c See Aquatic Macrophytes, Emergent
Plants, and Floating-leaved Plant Biomass.

In Florida:
Floating-leaved plants occur in many Florida
waterbodies. If the lake is shallow enough, rooted
floating-leaved plants can grow completely across
it. In Florida waterbodies where there are extensive
loose sediments, the roots of floating-leaved plants
that are anchored to the bottom provide the stable
surface that some species offish need for successful
spawning.
The stems of floating-leaved plants (like
spatterdock) often contain burrowing insects
called bonnet worms that many anglers use for
bait. In many Florida waterbodies, some float-
ing-leaved plants are considered a major aquatic
weed problem and require constant management
in order to maintain acceptably low levels. For
example, water hyacinths can grow so densely
that waterways become impassable.

Health Concerns:
Floating-leaved plants are not generally
thought of as a human health concern, although
they can create problematic situations. For ex-
ample, dense growths of floating-leaved plants
can entangle swimmers. Floating-leaved plants
may also provide habitat for animals like snakes
and alligators that may be dangerous under certain
conditions.

Floating-leaved Plant
Biomass
(as used by Florida LAKEWATCH) is the average
weight of fresh, live floating-leaved plants growing
in one square meter of a lake's bottom area. The
measurement of floating-leaved plant biomass in a
waterbody is one of several measurements that can
be used to assess a waterbody's overall biological
productivity.

c See Average Plant Biomass and
Biological Productivity.


In Florida:
Average floating-leaved plant biomass in
Florida lakes generally ranges from 0 to 19 kg wet
wt/m2. It appears to be linked with a waterbody's
biological productivity. This relationship can be
summarized as follows:
+ in biologically unproductive (oligotrophic) lakes,
the average floating-leaved plant biomass is about
1.0 kg wet wt/m2;
+ in moderately productive (mesotrophic) lakes,
the average floating-leaved plant biomass is about
1.5 kg wet wt/m2;
+ in highly productive (eutrophic) lakes, the
average floating-leaved plant biomass is about 2.0
kg wet wt/m2; and
+ in the most highly productive (hypereutrophic)
lakes, the average floating-leaved plant biomass is
about 3.0 kg wet wt/m2.

c See Trophic State and each of its
categories: Oligotrophic, Mesotrophic,
Eutrophic, and Hypereutrophic.

Frequency of
Occurrence
(of an aquatic plant) is an estimate of the relative
abundance of specific aquatic plants. Florida
LAKEWATCH determines the frequency of
occurrence using the following procedure:
+ A number of evenly-space locations are chosen
around a shore (usually 10 per lake, but up to 30
locations in a large lake). Locations are selected
so that they will give a reasonable representation
of the vegetation present in the waterbody.
+ At each location, a visual inventory is per-
formed in each of three areas one in the
emergent plant zone, one in the floating-leaved
plant zone, and one in the submersed plant zone.
+ The frequency of occurrence is the percentage
of locations at which a particular plant was seen.
For example, if ten locations were sampled and
the plant maidencane was seen at four of them,
the frequency of occurrence of maidencane
would be 40% (that is, 4 divided by 10, then
multiplied by 100%).








Fresh Plant
Weight .
is the weight offresh, live
plant material that has J
been collected from a
waterbody and shaken or
spun to remove excess
water. These plants are
considered to be "wet"/
because they are fresh and
full of intemal moisture.
The unit ofmeasure used
by Florida LAKEWATCH is "kilograms wet weight per
square meter" (abbreviated "kg wet wt/m2").

Geologic Region
is an area that has similar soils and underlying
bedrock features. The characteristics of the geologic
region in which a waterbody is located may be
responsible for the water's chemical characteristics
and trophic state. Geology can also have a signifi-
cant influence on the shape of a waterbody's basin, a
factor that affects many of a waterbody's features.

( See Lake Region, Morphometry, and
Trophic State.


Groundwater
is water that is underground. Groundwaters are
distinguished from "surface waters" which are found
on top of the ground. In Florida, groundwater resides
at different depths in several regions called aquifers.

Humic Acids
are produced when organic matter such as dead
leaves decay. Humic acids can color water so that it
appears reddish or reddish-brown, like tea. In some
cases, the water can appear almost black.

c- See Color.

Hydraulic Flushing Rate
is the rate at which water in a waterbody is replaced
by new water.


c( See Limiting Environmental Factors.

Hypereutrophic
is an adjective used to describe the level of
biological productivity of a waterbody. Florida
LAKEWATCH and many professionals classify
levels of biological productivity using four trophic
state categories oligotrophic, mesotrophic,
eutrophic, and hypereutrophic. Of the four
trophic state categories, the hypereutrophic state is
defined as having the highest level of biological
productivity. The prefix "hyper" means over
abundant. Hypereutrophic waterbodies are among
the most biologically productive in the world.
Hypereutrophic waterbodies generally have the
characteristics described below.
+ Hypereutrophic waterbodies have extremely
high nutrient concentrations.
*While hypereutrophic waterbodies can be
dominated by non-sportfish species (gizzard shad
and catfish), they can also support large numbers
and large sizes of sportfish including largemouth
bass, speckled perch, and bream.4
+ A hypereutrophic waterbody has either an
abundant population of algae or an abundant
population of aquatic macrophytes and some-
times it will support both.
+ Hypereutrophic waterbodies that are dominated
by algae are characterized by having high chloro-
phyll concentrations (greater than 40 pg/L). These
waterbodies will have reduced water clarity,
causing Secchi depth readings to be less than 1
meter (about 3.3 feet). In contrast, when aquatic
macrophytes instead of algae dominate a hyper-
eutrophic waterbody, its water can have lower
chlorophyll concentrations. The resulting water
clarity will be reflected in Secchi depth readings
that are greater, mimicking those of less biologi-
cally productive waterbodies.
+ Regardless of whether a waterbody is plant-
dominated or algae-dominated, typically it will
41 .. evaluated several ways by measuring "numbers
acre" and/or "weight acre. Fish can also be sampled
using one or more ofa variety of catch methods. Each combination of
measurement and samphng techniques may give i.. indications of
which fish are dominant in a waterbody.







have thick sediments on its bottom as the decaying
plant and/or algal debris accumulates.
+ Hypereutrophic waterbodies may experience
frequent algal blooms.
+ Oxygen depletion may also be a common cause
offish kills in these waterbodies.


c See Algae, Aquatic Macrophytes,
Chlorophyll, Fish Kill, Secchi Depth,
and Trophic State.


Teeming
with
life...


Newspapers and
other media have ,
been known to
characterize
hypereutrophic
lakes as being
"dead." However,
quite the reverse
is true. To say that
is true. To say that Line illustration courtesy of UF/FAS
a waterbody is CenterforAquat c and Invasi Plant
hypereutrophic
implies it's capable of producing and supporting
the greatest abundance of living organisms
such as plants, invertebrates, fish, and wildlife.


Iron
is a common element found in the soils of the earth.
Its chemical symbol is "Fe." Iron exists in either
ferrous (Fe") or ferric (Fe") forms.
The Role of Iron in Waterbodies:
Iron is an essential nutrient for aquatic
plants and algae. In addition, iron performs an
important function in aquatic systems through its
interaction with another nutrient, phosphorus.
Specifically, the presence of iron influences
whether phosphorus is in a form that can be used
by plants and algae. This relationship also
depends on whether adequate oxygen is present.
Here's what happens in the two cases:


Case 1 when oxygen is present in sufficient
amounts in the waterbody:
* iron will tend to bind with phosphorus;
* aquatic plants and algae cannot use phosphorus
in this form;
* the result may be that the growth of aquatic
plants and algae is limited.

Case 2 when oxygen is not present in sufficient
amounts in the waterbody:
* iron-phosphorus compounds dissolve;
* aquatic plants and algae can use phosphorus in
this dissolved form;
* the result may be that the growth of aquatic
plants and algae is increased.
Waterbody managers may try aerating iron-
rich waters as a strategy to reduce phosphorus
concentrations in order to limit nuisance aquatic
plant and algal growth, hoping for the results
described in Case 1. This effort may be thwarted,
however, if sulfur is plentiful in the water. Iron
has the chemical characteristic of preferring to
bind with sulfur instead of with phosphorus,
when there is adequate oxygen present, as with
an aerator. Therefore, in aerated sulfur-rich
waters, phosphorus would still be available for
aquatic plant and algae use, and the expected
decline in aquatic plant and algal growth would
not be realized.
An understanding of the role iron plays in the
phosphorus cycle is a particularly important man-
agement tool in waterbodies where the primary
supply of phosphorus is that which is dissolved
from the bottom sediments into the water column.
In this situation, iron manipulation is one of only a
few management strategies that have the potential
to limit phosphorus availability effectively.
In Florida:
Waterbodies in the Florida LAKEWATCH
database analyzed prior to January 1998, had
average total iron concentrations which ranged
from 0 to 2.4 mg/L. Over 75% of these water-
bodies had total iron concentrations less than
0.24 mg/L. The highest concentrations of iron are
found in Florida's highly colored waterbodies.
This is understandable, because iron combines


:







readily with organic molecules like those that make
water appear tea-colored, probably causing these
waterbodies to become iron enriched.
Health Concerns:
Iron is not considered a known threat to human
health. It may, however, be toxic to invertebrates and
fish. Canada has issued a guideline stating that total
iron should not exceed 0.3 mg/L, which is higher than
the concentration found in most Florida lakes. If iron
is a cause of toxicity to Florida's aquatic organisms,
and there is no evidence that it is, only a few Florida
lakes are potentially at risk.

Lake region
is a geographic area in which
lakes have similar geology, soils, ;-
chemistry, hydrology, and bio-
logical features. In 1997, using
Florida LAKEWATCH data
and other information, the
United States Environmental ProtectionAgency divided
Florida into 47 lake regions using these similarities as
their criteria.
Lakes in an individual lake region exhibit
remarkable similarities. However, lakes in one lake
region may differ significantly from those in a
different lake region. For example, most lakes in
the New Hope Ridge/Greenhead Slope lake region
in northwestern Florida (in Washington, Bay,
Calhoun, and Jackson Counties) tend to have lower
total nitrogen, lower total phosphorus, lower
chlorophyll concentrations and higher Secchi
depths when compared to other Florida lakes.
While lakes in the Lakeland/Bone Valley


A copy of Lake Regions of Florida can
be obtained by contacting the U.S.
Environmental Protection Agency at 200
SW 35th Street, Corvallis, OR 97333 and
requesting Publication EPA/R=97/127.
A color poster of the Florida Lake Regions
can be obtained from the Florida Depart-
ment of Environmental Protection (Talla-
hassee phone: 850/921-9918). These
sources are valid as of October, 1999.


Upland lake region in central Florida (in Polk and
Hillsborough Counties) tend to have higher total
nitrogen, higher total phosphorus, higher chloro-
phyll concentrations and lower Secchi depths when
similarly compared.
Using descriptions of lake regions, waterbody
managers can establish reasonable, attainable water
management goals for individual lakes. Lake
region characteristics can also be used to help
choose management strategies that are likely to be
effective in achieving management goals. In
addition, lakes with water chemistry that differs
markedly from that of other lakes in the same lake
region can be identified and investigated to deter-
mine the cause of their being atypical.
The lake regions are mapped and described in
Lake Regions of Florida (EPA/R=97/127). The
Florida LAKEWATCH Program can provide a free
handout describing: (1) how and why the lake
regions project was developed; (2) how to compare
your lake with others in its Lake Region; and (3)
how the Lake Region Classification System can be
useful to you.

Limiting Environmental
Factors
are factors whose presence or absence causes the
growth of aquatic plants and/or algae to be restricted.
Examples of some limiting environmental factors
are described below.
+ Suspended solids (tiny particles stirred up from
the bottom sediments or washed in from the water-
shed) can reach concentrations high enough that the
growth of plants and algae is limited because sun-
light is blocked out. This is a common situation in
shallow lakes, especially those with heavy wave
action like Lake Okeechobee in south Florida.
+ The color of dissolved substances, though clear,
can block sunlight and retard the growth of algae.
Many of Florida's lakes are tea-colored (reddish
or reddish-brown) because of dissolved organic
substances in the water. Even when tea-colored
lakes are rich in nutrients, the growth of algae and
submersed aquatic plants can be limited because
the colored water prevents sunlight from reaching
them.








+ The "hydraulic flushing rate" is the rate at which
water in a waterbody is replaced with new water.
The flushing rate can influence algal abundance
significantly. Waterbodies with high flushing rates
- such as many of Florida's springs, reservoirs, and
lakes that are actually just wide spots in rivers -
have low algal levels even though they may have
high nutrient concentrations. This seemingly
paradoxical condition exists because the algae are
flushed out of the system before they have the time
to grow to their maximum potential there.
+ Aquatic macrophytes should also be considered
as a limiting environmental factor, because their
presence may limit the growth of free-floating
algae in Florida waterbodies indirectly.
If macrophyte coverage (PAC) is less than
30% of a waterbody, the presence of macrophytes
does not appear to influence open-water algal
levels. However, lakes with aquatic macrophytes
covering over 50% of their bottom area typically
have reduced algal levels and clearer water.
SOne explanation is that either aquatic macro-
phytes, or perhaps the algae attached to them, use
the available phosphorus in the water, competing with
the free-floating algae for this necessary nutrient.
2 Another explanation is that the macrophytes
anchor the nutrient-rich bottom sediments in
place, buffering the action of wind, waves, and human
effects, and preventing re-suspension of nutrients into
the water column that can stimulate algal growth.
3 These same macrophytes act as a third type of
buffer by preventing wind and wave action
from re-suspending the actual algal cells and/or
other suspended solids into the water column. By
preventing algal cells from re-entering the water
column, macrophytes (plants) also act to inhibit
any further algal growth, due to the fact that the
algal cells are "lost" in the bottom sediments.
Often the management of a waterbody is
focused solely on the manipulation of nutrients as a
strategy for controlling growth of algae and/or
plants. However, a truly skilled manager will evalu-
ate all the potentially limiting environmental factors
and consider all the possibilities.
See Algae, Aquatic Macrophytes, Color,
Humic Acids, and Trophic State.


Limiting Nutrient
is a chemical necessary for plant growth that is
available in smaller quantities than needed for
aquatic plants and algae to achieve their maxi-
mum abundance. Once the limiting nutrient in a
waterbody is exhausted, algae stop growing. If
more of the limiting nutrient is added, larger
algal populations will result until their growth is
again limited by nutrients or by limiting environ-
mental factors.
In Florida waterbodies, nitrogen and phospho-
rus are most often the limiting nutrients. Aquatic
plants may not respond as directly to nutrient
limitation in the water as do algae because many of
these plants can also take their required nutrients
from the bottom sediments, through their roots, as
well as from the open-water.5
In most freshwater lakes in Florida, the limiting
nutrient is believed to be phosphorus. However, in
watersheds where the soils contain sizeable deposits
of phosphorus, nitrogen will usually be the limiting
nutrient. Nitrogen may be the limiting nutrient in
some saltwater systems. Less commonly, silica can
be the limiting nutrient in some waters. Trace
nutrients (like molybdenum and zinc) that are
necessary for the growth of plants and algae may
also be in limited supply in some circumstances.

See Limiting Environmental Factors,
Nitrogen, Phosphorus, and Silica.



Limnology
is the scientific study
ofthe physical, chemi-
cal, and biological
characteristics of
inland (non-marine)
aquatic systems. A "7
limnologist is a scientist
who studies limnology.



5Atlas c ; .1990.
University Dress, Photo by JoeRichard
Edmonton, Canada.








Morphometry (Morphometric)
is the measurement of shapes. Morphometric
parameters of a waterbody can be best understood
by looking at a detailed map of the waterbody,
preferably a map showing the contours of the
bottom (called a bathymetric map). Morphometric
parameters of a waterbody also include its mean
depth, maximum depth, shoreline length, volume,
and size of its basin. These characteristics significantly
affect all aspects of how a waterbody functions.

c See Mean depth.

Nitrogen
is an element that, in its different forms, stimulates the
growth of aquatic macrophytes and algae in water-
bodies. Nitrogen is represented in the Periodic
Table of Elements as N.

ce See Limiting nutrient, Nutrients,
and Total nitrogen.


Nutrients
are chemicals that algae
and aquatic macrophytes
need for growth. Nitro-
gen and phosphorus are
the two most influential
nutrients in Florida
waterbodies. Nutrients in
waterbodies can come
from a variety of sources.
In most cases Florida LAKEWATCH
nutrients are carried volunteers collect monthly
samples for nutrient analysis.
into a waterbody
primarily when water drains through the surround-
ing rocks and soils, picking up nitrogen and phos-
phorus compounds along the way. For this reason,
knowledge of the geology and physiography of an
area can provide insight into how much nutrient
enrichment can be reasonably expected in an
individual waterbody from this natural source.
For example, lakes in the New Hope Ridge/
Greenhead Slope lake region in northwestern
Florida (in Washington, Bay, Calhoun, and
Jackson Counties) can be expected to have low


nutrient levels because they are in a nutrient-poor
geographic region. Whereas, lakes in the Lakeland/
Bone Valley Upland lake region in central Florida
(in Polk and Hillsborough Counties) can be ex-
pected to have very high nutrient levels because the
land surrounding the lakes is nutrient-rich.
There are many other sources of nutrients,
however, and they are generally not as substantial
as nutrient contributions from surrounding rocks
and soils. Some occur naturally, and others are
the result of human activity. For example nutri-
ents are conveyed in rainfall, stormwater runoff,
seepage from septic systems, bird and animal
feces, and the air itself. Most nutrients can move
easily through the environment. They may come
from nearby woods, farms, yards, and streets -
anywhere in the watershed.

c See Algae, Aquatic macrophytes,
Chlorophyll, Lake regions, Limiting nutrients,
Total nitrogen and Total phosphorus.


Oligotrophic
is an adjective used to describe the level of biological
productivity of a waterbody. Florida LAKEWATCH
and many professionals classify levels of biological
productivity using four trophic state categories -
oligotrophic, mesotrophic, eutrophic, and
hypereutrophic.
Of the four trophic state categories, the
oligotrophic state is defined as having the lowest
level of biological productivity. (The prefix
"oligo" means scant or lacking.)
An oligotrophic waterbody is capable of
producing and supporting relatively small popula-
tions of living organisms (plants, fish, and wildlife).
The low level of productivity in oligotrophic
waterbodies may be the result of low levels of
limiting nutrients in the water, particularly nitrogen
or phosphorus, or by other limiting environmental
factors.
Oligotrophic waterbodies generally have
the following characteristics:
* Nutrients are typically in short supply, and
aquatic macrophytes and algae are less abundant.
* Oligotrophic waterbodies typically have less plant








debris accumulated on the bottom over the years
since aquatic macrophytes and algae are less abundant.
* Oligotrophic waterbodies often tend to have
water clarity greater than 13 feet, due to low
amounts of free-floating algae in the water
column. The clarity may be decreased however,
by the presence of color (from dissolved sub-
stances), stirred-up bottom sediments, or
stormwater runoff (particulate matter).
* Fish and wildlife populations will generally be
small, because food and habitat are often limited.
Oligotrophic waterbodies usually do not support
abundant populations of sportfish such as large-
mouth bass and bream, and it usually takes longer
for individual fish to grow in size. Fishing may be
good initially if the number of anglers is small, but
can deteriorate rapidly when fishing pressure
increases and fish are removed from the waterbody.
* A waterbody may have oligotrophic character-
istics even though it has high nutrient levels.
This can occur when a factor other than nutrients
is limiting the growth of aquatic macrophytes
and algae. For example, a significant amount of
suspended sediments (stirred-up sediments or
particles washed in from the watershed) or
darkly colored water can retard macrophyte and
algae growth by blocking sunlight.

ce See Color, Limiting environmental
factors, Limiting nutrient, Nutrients,
Secchi depth, Total nitrogen, Total
phosphorus, Trophic state, and
Water clarity.


Looks can be deceiving...
Because oligotrophic waterbodies typically
have such clear water (Secchi depth readings
greater than 13 feet), people often mistakenly think
these waters are pure and healthy for human
consumption. Unfortunately, human disease and
death can be caused by bacteria, pathogens, and
other toxic substances that are invisible to the
naked eye. It should not be assumed that any
surface water is safe to drink no matter how
clear it looks. It should also be noted that in Florida,
fish having some of the highest levels of mercury
have been caught in oligotrophic waters.


PAC
is an abbreviation for
percent area covered
and is a measure of the
percentage of the bottom
area of a waterbody with
aquatic macrophytes
growing on, or over it.
Aquatic scientists use
PAC to assess the abun-
dance and importance of
aquatic plants in a waterbody.
Waterbodies in the Florida LAKEWATCH
database analyzed prior to January 1998 had PAC
values ranging from 0 to 100%. PAC values are
linked with the biological productivity trophicc
state) of waterbodies:
* In the least productive (oligotrophic) waterbod-
ies, PAC values are usually low. In rare cases where
they are high (occasionally reaching 100%), it is
usually because a thin layer of small plants is
growing along the bottom.
* In moderately productive (mesotrophic) and
highly productive (eutrophic) waterbodies, PAC
values are generally greater than those measured in
oligotrophic waterbodies, and the average plant
biomass is also greater.
* In extremely productive (hypereutrophic) water-
bodies dominated by planktonic algae, PAC values
are often less than 25%. In Florida however, many
hypereutrophic waterbodies contain mostly aquatic
macrophytes, not algae. In these cases, PAC values
often tend to be greater than 75%.

c* See Algae, Aquatic macrophyte, Average
plant biomass, and Trophic state.


Particulates
are any substances in small particle form that are
found in waterbodies, often suspended in the water
column. Substances in water are either in particulate
form or dissolved form. Passing water through a
filter will separate these two forms. A filter will trap
most of the particulates, allowing dissolved sub-
stances to pass through.


20








Periphyton
are algae attached to underwater objects such as
aquatic plants, docks, and rocks. There are several
types of periphyton. They're named according to
where they grow as follows:
+ epiphytic algae grow on the surface of aquatic plants;
+ epipelic algae are attached to sediments;
+ epilithic algae are attached to rocks; and
+ benthic algae grow along the bottom of a water-
body (including epipelic and epilithic algae).
Periphyton communities contribute to a
lake's overall biological productivity. Not only
do they provide food and habitat for fish and
invertebrates, but they can also affect nutrient
movement through the aquatic ecosystem in
important ways. For example, when periphyton
are abundant, they can absorb nutrients from the
water so effectively that the growth of free-
floating forms of algae may be restricted.
Periphyton are not typically measured by
Florida LAKEWATCH. Water samples taken by
LAKEWATCH volunteers are used to measure
only free-floating algae, called phytoplankton,
suspended in the water column.

ce See Algae, Biological productivity,
Nutrients, Phytoplankton, and
Water clarity.


pH
is a scale of numbers from 0 through 14 that is used
to indicate the acidity of a waterbody. Water is said
to be acidic if the pH is below 7, and basic when the
pH is above 7. A pH value of 7 is considered
neutral, which means it's neither acidic or basic.
The scientific definition of pH is "the negative
logarithm of the hydrogen ion (H+) concentration."
It's important to note that each one of the 14
increments on the pH scale represents a ten-fold
change in acidity. For example, lake water with a
pH of 5.0 is ten times more acidic than lake water
with a pH of 6.0. Scales used in this manner are
"logarithmic" like the Richter scale used for
determining earthquake intensity.


The Role of pH
in Waterbodies:
pH influences aquatic biological systems in a
variety of ways. In the early years of the 20th
century, pH was regarded as the "master variable"
and was routinely studied by aquatic scientists in an
attempt to understand its complex role. Studies
have established that the pH values in waterbodies
range from less than 4 to over 10. Waterbodies in
the low end of the pH scale are of particular interest
to scientists concerned about the effects of acid
rain on aquatic plants, fish, and wildlife.
In Florida:
Waterbodies in the Florida LAKEWATCH
database analyzed prior to January 1998 had pH
values ranging from less than 4 to nearly 12.
Approximately half of the Florida lakes sampled
have pH values between 5.8 and 7.8.

c* See Water quality (for Florida standards).

The location of a waterbody has a strong
influence on its pH. For example, lakes in the
Okefenokee Plains lake region in north Florida (in
Baker, Columbia, and Hamilton Counties) tend to
have pH values below 4.8, and lakes in the Lake-
land/Bone Valley Upland lake region in central
Florida (in Polk and Hillsborough Counties) tend to
have values above 7.5.

- See Lake region.


Fish, plants and wildlife have different
sensitivities to pH. For example, the young of
some fish species cannot survive in water that
has a pH below 5.0. However, with few excep-
tions, lakes with low pH in Florida are able to
support healthy fish populations.
Most living organisms in Florida systems
appear to be well adapted to acidic conditions,
possibly because low pH seems to be a naturally-
occurring environmental factor. Consequently,
many aquatic scientists do not consider acid rain
to be as great a threat to Florida's waterbodies as
it is to those in the northeastern United States.







Health Concerns:
pH is not generally thought of as a known
human health concern. However, when pH is lower
than 5.0, some people experience eye irritation.
pH is important in municipal drinking
water supplies. The acceptable range of pH for
drinking water is generally from 6.5 to 8.5. This
range, however, is not based on direct health
concerns, but is primarily based on minimizing
the corrosion and encrustation of metal water
pipes. However, pH can affect drinking water
supplies as described below.
* When pH is lower than 6.5 or exceeds 8.5,
chlorine in drinking water supplies becomes a less
effective disinfectant.
* When pH is lower than 6.5 or exceeds 8.5,
chlorine in drinking water supplies can contribute
to the formation of cancer-causing trihalomethanes.
* When pH of drinking water is in the acidic
range, it can cause copper pipes and lead soldering
in pipes to dissolve.

Phosphorus
is an element that, in its different forms, stimulates the
growth of aquatic macrophytes and algae in water-
bodies. Phosphorus is represented in the Periodic
Table of Elements as P.
ce See Limiting nutrient, Nutrients, and
Total phosphorus.

Physiographic region
is a geographic area whose boundaries enclose
territory that has similar physical geology (i.e., soil
types, land formations, etc.).

Phytoplankton
are microscopic, free-floating
aquatic plant-like organisms
suspended in the water column.
They are sometimes called
planktonic algae or just algae.
Though individual phytoplankton are tiny in size,
they can have a major influence on a waterbody.
For example, phytoplankton abundance often
determines how biologically productive a water-
body can be; small amounts of phytoplankton often


result in less fish and wildlife. Also, the public is
concerned about the abundance of phytoplankton,
because it significantly affects water clarity.
Aquatic scientists assess phytoplankton
abundance by estimating its biomass. This is known
as "relative abundance." Two common methods
used are: (1) viewing phytoplankton through a
microscope and counting each organism, and (2)
measuring chlorophyll concentrations in water
samples. Florida LAKEWATCH uses the chlorophyll
method because it's faster and less costly.

c See Algae and Chlorophyll.

Planktonic algae

c See Phytoplankton.

Plant biomass

ce See Average plant biomass.


Plant frequency (%)

ce See Frequency of occurrence.


Plant species

c See Common plant name and Scientific
plant name.

Potassium
is an important mineral and a nutrient necessary for
plant growth. It's found in many soils and constitutes
a little over 2% of the earth's crust. Natural sources of
potassium are numerous in aquatic environments.
Man-made sources include industrial effluents
Sand run-off from agricultural areas. (Potassium is
W used extensively in crop fertilizers.) Its chemical
symbol from the Periodic Table of Elements is K.
The Role of Potassium in Waterbodies:
Because potassium salts are readily soluble in
water, potassium is found primarily in dissolved
form in waterbodies rather than in particulate form.
The concentration of potassium in natural
surface water is generally less than 10 mg/L, but


22








potassium concentrations as high as 100 mg/L can
occur. Potassium is essential to plant and animal
nutrition. Because potassium concentrations in
freshwaters are generally adequate for meeting the
nutritional needs of the biological community,
potassium is not usually considered as being a
limiting nutrient like phosphorus and nitrogen.

r See Limiting nutrient and Particulates.

In Florida:
Waterbodies in the Florida LAKEWATCH
database analyzed prior to January 1998 had
potassium levels ranging from 0 to 50 mg/L.
Over 75% of these waterbodies had potassium
concentrations less than 3.2 mg/L. Higher potas-
sium concentrations generally occur naturally along
the coast, because marine waters have higher
average potassium concentrations than freshwater.
If potassium concentrations in a coastal area
waterbody are uncharacteristically high, it may
indicate saltwater is seeping through the ground
into the waterbody, called saltwater intrusion.
Health Concerns:
Potassium concentrations at the levels found
in freshwaters cause no known direct or indirect
human health problems.

PVI
is a measure of the percentage
of a waterbody's volume
that contains aquatic
macrophytes. Historically,
PVI was an abbreviation
for the phrase percent r
volume infested with
:; 't~i ..
aquatic plants. Recently it
has become an abbreviation
for the more neutral phrase
percent volume inhabited. Regardless of the
terminology, PVI is used to assess the abundance
and importance of aquatic macrophytes in a
waterbody.


er See Algae, Aquatic macrophyte, Average
plant biomass, and Trophic state.


In Florida:
Waterbodies in the Florida LAKEWATCH
database analyzed prior to January 1998 had PVI
values ranging from 0 to 100%. In Florida, PVI values
are strongly linked with the biological productivity
trophicc state) of waterbodies as described below:
* In the least biologically productive (oligotrophic)
waterbodies, PVI values are generally very low.
* In moderately biologically productive (mesotrophic)
waterbodies and highly productive (eutrophic)
waterbodies dominated by aquatic plants, PVI
values are higher than those measured in oligotrophic
waterbodies.
* Highly biologically productive (hypereutrophic)
waterbodies dominated by algae usually have very
low PVI values. Hypereutrophic waterbodies
dominated by aquatic plants, usually have very
high PVI values.

Salinity
is the saltiness of water and is influenced by leaching
rock and soil formations, runoff from a watershed,
atmospheric precipitation and deposition, and
evaporation. It is measured in units of parts per
thousand (abbreviated "ppt"). The Atlantic Ocean
and the Gulf of Mexico typically have salinity values
around 35 ppt, although there is significant variation,
particularly in near shore areas. Salinity often tends
to be lower in areas receiving inflows of freshwater,
like the mouths of rivers. Salinity often tends to be
higher in areas where the evaporation rate is high -
in hot, dry climates.

- See Chloride, Sodium, and
Specific conductance.


23








Scientific plant name
is a name used by scientists to help avoid the
confusion caused by the use of common plant
names, which often tend to be inconsistent.
Professionals have assigned a unique scientific
name to each plant. Scientific names are usually
based on Latin or Greek words and are written in
italics or underlined. For example, the aquatic
plant whose common name is maidencane has
the scientific name Panicum hemitomon.
A scientific plant name consists of two parts.
The first part is called the "family name" or genus
and the second part refers to the species. For example,
Potomogetonpectinatus is the scientific name of a
specific species of pondweed. Potomogeton is the
genus and pectinatus is the species. Potomogeton
illinoensis is a different species of pondweed. By
using scientific names, containing both genus and
species, scientists can be very specific.

c See Common plant name and Plant species.

Secchi depth
is a measurement that
indicates water clarity.
Traditionally, the transpar-
ency or water clarity of a
waterbody is measured using
an 8-inch diameter disc
called a Secchi disc- named
for its inventor, Pietro
Angelo Secchi. A Secchi
disc is usually painted in
alternating quadrants of
black and white, though it LAKEWATCH uses solid white
can also be solid white. A Secchi discs, as shown here.
cord is attached through the center of the disc and
is marked off in intervals, usually in feet or meters.
To measure water clarity, the disc is lowered
into the water to find the depth at which it first
vanishes from the observer's sight. (Note: if the
disc can still be seen as it rests on the lake bottom
or if it disappears into plant growth, the depth at
which this happens is not considered the Secchi
depth.)


Silica
is the name for compounds containing silicon in
combination with oxygen. Silicon is the second
most abundant element in the earth's crust, and
silica is found in all waterbodies. Silica generally
occurs in freshwaters in both dissolved and
particulate forms. Silicon is represented in the
Periodic Table of Elements as Si and the chemical
formula for soluble silica is H4SiO,.
Although human activities (i.e., fluoridation of
drinking water and some industrial processes), are
sources of silica, even pristine waters contain silica
compounds. Many freshwaters contain less than 5
mg/L of silica, while concentrations as high as 4000
mg/L have been measured in saline waterbodies.
The Role of Silica in Waterbodies:
Silica is considered an essential micronutrient
for microorganisms and diatoms (a type of algae).
These organisms use silica to form shells and
other protective structures. Diatoms are capable of
using large amounts of silica, and diatom popula-
tions may be limited when silica is in short supply.
Silica concentrations in water are affected by
several mechanisms. For example:
* As diatom populations increase, the rate at
which they pull silica from the water also
increases (usually in the Spring). This can result
in a decline of silica concentrations in the water.
* Silica is removed from the water column alto-
gether when diatoms die and sink to the bottom,
forming silica-enriched sediments.
* When pH is above 7, the amount of dissolved
silica in the water column is affected by the
presence of iron and aluminum; either one can reduce
the amount of dissolved silica in the water column.
* The amount of silica in the water column can
increase when humic compounds (organic sub-
stances that make water tea-colored) are present.
In Florida:
Waterbodies in the Florida LAKEWATCH
database analyzed prior to January 1998 had silica
levels ranging from 0 to about 14 mg/L. Over 75%
of these waterbodies had silica concentrations less
than 2.4 mg/L.


c- See Water clarity.


24








Health Concerns
Silica poses no known threat to human
health at the concentrations found in waterbodies.

Sodium
is the sixth most abundant element on earth. Sodium
is often associated with chloride; common table
salt is mostly sodium chloride. Sodium is used
extensively in industrial processes, food processing,
and in some water softening devices. Sodium is
represented in the Periodic Table of Elements as Na.
The Role of Sodium
in Waterbodies:
All waters contain sodium. Sodium is essential
to all animals and some microorganisms and plants.
Generally, sodium is not considered a limiting factor
for freshwater organisms, unless sodium concentra-
tions reach levels at which freshwater organisms
cannot survive. As sodium concentrations increase in
a waterbody, there can be a continuous transition
from freshwater organisms to those adapted to
brackish water and then ultimately, to marine
(saltwater) organisms. High sodium concentrations
can be expected in the following:
+ areas near the coast that receive sodium-enriched
groundwater from saltwater intrusion;
+ areas where evaporation is excessive (perhaps in
hot and/or dry climates); and
+ areas receiving human pollution including
agricultural runoff containing fertilizer residues,
discharges containing human or animal waste,
and backwash from water softeners using the
sodium exchange process.

c* See Chloride, Salinity, Surface water, and
Limiting nutrient.

In Florida:
Waterbodies in the Florida LAKEWATCH
database analyzed prior to January 1998 had
sodium concentrations which ranged from 1 to
over 1100 mg/L. Over 75% of these waterbodies
had sodium concentrations less than 13 mg/L.
The higher concentrations of sodium are found
in lakes located near the coast and in lakes where
the groundwater entering the lakes has been in
contact with natural salt deposits.

25


Health Concerns:
At the concentrations found in freshwaters,
sodium generally causes no known direct threat
to human health.

Specific conductance
is a measure of the capacity of water to conduct
an electric current. A higher value of conductance
means that the water is a better electrical conductor.
The unit of measure for conductance can be
expressed in two ways:
+ microSieman per centimeter of water mea-
sured at a temperature of 25 degrees Celsius
(abbreviated [S/cm @ 250 C).
+ Micromhos per centimeter (abbreviated
micromhos/cm or [mhos/cm).

The Role of Specific Conductance in
Waterbodies:
Specific conductance increases when more of
any salt including the most common one, sodium
chloride, is dissolved in water. For this reason,
conductance is often used as an indirect measure of
the salt concentration in waterbodies. In general,
waters with more salts are the more productive ones
- except, of course, where there are limiting
nutrients or limiting environmental factors involved.
Natural factors can also cause higher conduc-
tance values in the open water. For example,
drought conditions can increase the salt concen-
trations in a waterbody in two ways: (1) drought
can cause inflowing waters to have higher salt
concentrations, and (2) heat and low humidity
can increase the rate of evaporation in open
water, leaving the waterbody with a higher
concentration of salt.
Because animal and human wastes (sewage,
feed lot effluent, etc.) contain salts, the measurement
of conductance can be used for the detection of
contamination. Since most discharges of indus-
trial and municipal wastewater directly into lakes
in Florida have been stopped, measurements of
conductance are now used in this context prima-
rily to detect septic tank seepage along shore-
lines. It's important to keep in mind that elevated
conductance measurements may have various
causes and do not by themselves prove there is
contamination from human or animal wastes.








ce See Biological productivity, Chloride,
Limiting environmental factors, Limiting
nutrient, Salinity, and Sodium.


In Florida:
Waterbodies in the Florida LAKEWATCH
database analyzed prior to January 1998 had
average conductance values that ranged from 11 to
over 5500 0iS/cm @ 250 C. Over 75% of these
waterbodies had conductance values less than
190 0S/cm @ 250 C.
The location of a waterbody has a strong
influence on its conductance. For example, lakes
in the New Hope Ridge/Greenhead Slope lake
region in northwestern Florida (in Washington,
Bay, Calhoun, and Jackson Counties) tend to have
conductance values below 20 6iS/cm @ 250 C.
While lakes in the Winter Haven/Lake Henry
Ridges lake region in central Florida (in Polk County)
tend to have values above 190 6iS/cm @ 250 C.

c See Water quality (for Florida standards).

Health Concerns:
There are no known human health concerns
directly related to specific conductance. In waters
where human or animal waste contamination is
suspected, bacterial tests should be conducted
regardless of whether conductivity values are high.

c See Lake region.



Submersed plants
are large plants that grow primarily below the
water's surface. Eelgrass, hydrilla, and coontail are
examples of submersed plants. Some of these
plants are rooted to the waterbody's bottom sedi-
ments, like eelgrass and hydrilla; while some, like
coontail, are not.


ce See Aquatic macrophytes.


Submersed vegetation provides habitatfor fish. Many
aquatic scientists consider this its most important role.

The Role of Submersed Aquatic Plants in
Waterbodies:
The importance of having submersed vegeta-
tion and the amount of submersed vegetation
necessary to achieve specific management goals
are both subjects of ongoing research and debate at
the present time. In general, submersed aquatic
plants perform several functions in waterbodies.
Some of them are described below.
* Submersed vegetation provides habitat for fish.
Many aquatic scientists consider this its most impor-
tant role.
* Submersed vegetation provides food and habitat
for wildlife populations (fish, ducks, invertebrates).
* Submersed vegetation affects nutrient cycles and
other chemical cycles in complex ways.
* Submersed vegetation can increase water clarity.
* Submersed vegetation stabilizes bottom sediments.
* Submersed vegetation can increase or decrease
dissolved oxygen concentrations, depending on its
abundance and the availability of light.
* Submersed vegetation contributes to the filling-in
of waterbodies by depositing decayed material that
accumulates on the bottom.

c See Aquatic macrophytes and
Submersed plant biomass.


26







In Florida:
Submersed plants occur in virtually all
Florida waterbodies. In an individual waterbody,
the availability of light, water clarity, water depth,
and sediment stability affect where submersed
plants will grow.
Professional management of aquatic plants
in Florida is extensive, because native and non-
native submersed plants can reach nuisance
levels. An abundance of submersed aquatic
plants can adversely affect recreational boating,
swimming, fishing, and fish populations. Also,
some people find submersed aquatic plants to be
aesthetically unappealing.
Health Concerns:
Submersed plants are not generally consid-
ered a danger to human health, but they can
cause problems indirectly in some circum-
stances. For example:
* submersed plants can camouflage underwater
objects, obstructing the ability of swimmers and
boaters to see potential hazards;
* submersed plants can entangle swimmers.

Submersed plant
biomass
(as used by Florida LAKEWATCH) is the average
weight of fresh, live submersed aquatic macrophytes
growing in one square meter area of a waterbody.
The measurement of the average submersed plant
biomass is one of several measurements that can
be used to assess a waterbody's overall biological
productivity and to assess the potential importance
of submersed plants.

ce See Average plant biomass and
Biological productivity.

In Florida:
Waterbodies in the Florida LAKEWATCH
database analyzed prior to January 1998 had an
average fresh weight of submersed plants ranging
from 0 to over 22 kg wet wt/m2. The biological
productivity of a waterbody is strongly related to
submersed plant biomass. This relationship is
summarized as follows:


* In biologically unproductive (oligotrophic)
waterbodies, the average submersed plant biomass
is about 0.5 kg wet wt/m2.
* In moderately productive (mesotrophic) water-
bodies, the average submersed plant biomass is
about 1.0 kg wet wt/m2.
* In highly productive (eutrophic) waterbodies, the
average submersed plant biomass is about 2.0 kg
wet wt/m2.
* In the most highly productive (hypereutrophic)
waterbodies, where algae are not the dominant
plants, the average submersed plant biomass is
about 5.0 kg wet wt/m2.

c* See Trophic state and each of its
categories: Oligotrophic, Mesotrophic,
Eutrophic, and Hypereutrophic.



Sulfates
are chemical compounds that contain the elements
sulfur and oxygen. They are widely distributed in
nature and can be dissolved into waterbodies in
significant amounts. The chemical formula for
sulfates is SO4=.
There are a variety of diverse sources for
sulfates in waterbodies. Sulfate concentrations in
a waterbody are influenced primarily by natural
deposits of minerals and organic matter in its
watershed. Sulfate is also widely used in industry
and agriculture, and many wastewaters contain
high concentrations of sulfate. Acidic rainfall
(containing sulfuric acid) is a major source of
sulfate in some waterbodies.
The primary source of sulfate in rain in
industrialized areas is through atmospheric
discharges from power plants that burn sulfur-
containing fuels and from certain industries.
The primary source of sulfate in rain in
non-industrialized areas is through atmospherically
oxidized hydrogen sulfide (the chemical symbol
for hydrogen sulfide is H S) which is produced
along coastal regions by anaerobic bacteria.
Volcanic emissions also contribute sulfur to the
atmosphere.







The Role of Sulfur in Waterbodies:
Sulfate is used by all aquatic organisms
for building proteins. Sulfur changes from one
form to another (known as "cycling") in quite
complex ways. Sulfur cycling can influence the
cycles of other nutrients like iron and phosphorus
and can also affect the biological productivity and
the distribution of organisms in a waterbody.
Bacteria can significantly influence the
sulfur cycle in water. For example, under conditions
where dissolved oxygen is lacking, certain bacteria
can convert sulfate to hydrogen sulfide gas
(H2S). Hydrogen sulfide gas has a distinctive
rotten egg smell, and in high concentrations can
be toxic to aquatic animals and fish.

cr See Biological productivity
and Nutrients.

In Florida:
Waterbodies in the Florida LAKEWATCH
database analyzed prior to January 1998 had
sulfate concentrations which ranged from 0 to
about 500 mg/L. Over 75% of these waterbodies
had concentrations of sulfates less than 20 mg/L.
Health Concerns:
Sulfates pose no known direct threat to
human health. In some Florida lakes, the decom-
position of large deposits of organic matter along
the shorelines will cause the formation of pockets
of hydrogen sulfide gas in the bottom sediments.
On the rare occasion when people step into these
pockets, they can experience a burning sensation
on their skin. Florida natives may refer to these
sediments as "hot mud."

Surface
water
is water found on the
earth's surface. It is
distinguished from
groundwater which UF/iAsceifrAquaandinvvePlan
is found underground.
Surface waters include many types of waterbodies
such as lakes, rivers, streams, estuaries, ponds and
reservoirs.


Total alkalinity
is a measure of water's capacity to neutralize acids.
Total alkalinity is often abbreviated TALK. The unit
of measure for total alkalinity is generally milligrams
per liter of total alkalinity as equivalent calcium
carbonate (abbreviated mg/L as CaCO3). Even
though alkalinity is expressed in units that reference
calcium carbonate, alkalinity levels are not determined
by calcium carbonate alone.
The alkalinity of a waterbody is influenced by
the soils and bedrock minerals found in its water-
shed and by the amount of contact the water has
had with them. For example, lakes in limestone
regions, which are rich in calcium carbonate, often
tend to have higher values for alkalinity. Those in
sandy soil regions, which are poor in calcium
carbonate, often tend to have lower values.
Alkalinity (and its opposite, acidity) can
also be influenced significantly by the presence
of several different substances, for example:
* phosphorus (in phosphatic soils and rocks);
* nitrogen (from ammonia);
* silica (from silicates);
* organic acids (like humic acids); and
* gases (specifically carbon dioxide and hydrogen
sulfide).

c- See pH.

When alkalinity is a concern, it's generally
related to the formation of a crusty accumulation of
calcium deposits, called scale, in tanks and pipes.

c See Calcium.

The Role of Alkalinity in Waterbodies:
Total alkalinity is a major determinant of
the acid neutralizing capacity (ANC) of water-
bodies. High alkalinity waters are often more
biologically productive than low alkalinity
waters. Consequently, total alkalinity was once
used as an indirect measure of a lake's produc-
tivity. In recent years, research has shown that
waterbodies with low alkalinity levels are more
susceptible to the effects of acidic water inputs
such as acid rain.


28







In Florida:
Waterbodies in the Florida LAKEWATCH
database analyzed prior to January 1998 had total
alkalinity concentrations ranging from 0 to over
300 mg/L as CaCO3. Over 75% of these waterbod-
ies had total alkalinity concentrations less than 35
mg/L as CaCO3.

- See Water quality (for Florida standards).

The location of a waterbody has an especially
strong influence on its total alkalinity concentra-
tion. For example, lakes in the Okefenokee Plains
lake region in north Florida (in Baker, Columbia,
and Hamilton Counties) tend to have total alkalin-
ity values of 0 mg/L as CaCO3. While lakes in the
Tsala Apopka lake region in central Florida (in
Citrus, Sumter, and Marion Counties) tend to have
values above 40 mg/L as CaCO3.

c See Lake region.

Health Concerns:
There is no known level of total alkalinity
in Florida waterbodies that indicates a threat to
human health.

Total chlorophyll
is a measure of all types of chlorophyll.
The abbreviation for total chlorophyll is TCHL.

c See Chlorophyll.


Total nitrogen
is a measure of all the various forms of nitrogen
that are found in a water sample. Nitrogen is a
necessary nutrient for the growth of aquatic plants
and algae. Not all forms of nitrogen can be readily
used by aquatic plants and algae, especially nitro-
gen that is bound with dissolved or particulate
organic matter. The chemical symbol for the
element nitrogen is "N," and the symbol for total
nitrogen is "TN."
Total nitrogen consists of inorganic and
organic forms. Inorganic forms include nitrate
(NO3 ), nitrite (NO2 ), unionized ammonia (NH4),

29


A Better

Way...
Chlorophyll measure-
ments are useful in
assessing the trophic
state of a body of water. -
However, the use of
chlorophyll measure-
ments alone may
produce misleading -
results; chlorophyll
measurements don't LAKEWATCH volunteers
take into account the filter lake water o obtain
biological productivity
expressed in the form of aquatic macrophytes.
Assessments that also include aquatic plant
abundance would be more accurate, particularly
in waterbodies with significant macrophyte
populations.

ce See Aquatic macrophytes and
Chlorophyll.


ionized ammonia (NH3,), and nitrogen gas (Na).
Amino acids and proteins are naturally-occurring
organic forms of nitrogen. All forms of nitrogen are
harmless to aquatic organisms except unionized
ammonia and nitrite, which can be toxic to fish.
Nitrite is usually not a problem in waterbodies,
however, because (if there is enough oxygen
available in the water for it to be oxidized) nitrite
will be readily converted to nitrate.

ce See Nitrogen.

The Role of Nitrogen
in Waterbodies:
Like phosphorus, nitrogen is an essential
nutrient for all plants, including aquatic plants and
algae. In some cases, the inadequate supply of TN in
waterbodies has been found to limit the growth of
free-floating algae (i.e., phytoplankton). This is
called nitrogen limitation, and occurs most com-
monly when the ratio of total nitrogen to total
phosphorus is less than 10 (in other words, the TN
concentration divided by the TP concentration is less
than 10 or TN/TP < 10). TN in water comes from
both natural and man-made sources, including:








* air (some algae can "fix" nitrogen pulling it
out of the air in its gaseous form and converting it
to a form they can use);
* stormwater run-off, including natural run-off
from areas where there is no human impact (nitro-
gen is a naturally-occurring nutrient found in soils
and organic matter);
* fertilizers; and
* animal and human wastes (sewage, dairies,
feedlots, etc.).

c* See Algae, Algal biomass, Chlorophyll,
Limiting nutrient, and Phytoplankton.


In Florida:
Waterbodies in the Florida LAKEWATCH
database analyzed prior to January 1998 had total
nitrogen concentrations which ranged from less than
50 to over 6000 itg/L. Using these average concentra-
tions of total nitrogen from this same database, Florida
lakes were found to be distributed into four trophic
states as follows.6
* approximately 14% of these lakes (those with
TN values less than 400 tig/L) would be classified
as oligotrophic;
* about 25% of these lakes (those with TN values
between 401 and 600 tig/L) would be classified as
mesotrophic;
* 50% of these lakes (those with TN values be-
tween 601 and 1500 tig/L) would be classified as
eutrophic; and
* nearly 11% of these lakes (those with TN values
greater than 1500 tig/L) would be classified as
hypereutrophic.


See Trophic state and each of its categories:
Oligotrophic, Mesotrophic, Eutrophic, and
Hypereutrophic; and Water quality.


6 F distribution of trophic state is based solely on total
nitrogen values without utilizing on total
phosphorus, chlorophyll, water clarity, or aquatic
macrophyte abundance.


The location of a waterbody has a strong
influence on its total nitrogen concentration. For
example, lakes in the New Hope Ridge/Greenhead
Slope lake region in northwestern Florida (in Wash-
ington, Bay, Calhoun, and Jackson Counties) tend to
have total nitrogen values below 220 itg/L. While
lakes in the Lakeland/Bone Valley Upland lake
region in central Florida (in Polk and Hillsborough
Counties) tend to have values above 1700 itg/L.

c See Lake region.

Health Concerns:
The concentration of total nitrogen in a water-
body is not a known direct threat to human health. It
is the individual forms of nitrogen that contribute to
the total nitrogen measurement and the use of the
water that need to be considered. For example,
nitrate in drinking water is a concern. Drinking water
with nitrate concentrations above 45 mg/L has been
implicated in causing blue-baby syndrome in infants.
The maximum allowable level of nitrate, a compo-
nent of the total nitrogen measurement, is 10 mg/L in
drinking water. Concentrations of nitrate greater than
10 mg/L generally do not occur in waterbodies,
because nitrate is readily taken up by plants and
used as a nutrient.

Total phosphorus
is a measure of all the various forms of phosphorus
that are found in a water sample. Phosphorus is an
element that, in its different forms, stimulates the
growth of aquatic plants and algae in waterbodies.
The chemical symbol for the element phosphorus is
P and the symbol for total phosphorus is TP. Some
phosphorus compounds are necessary nutrients for
the growth of aquatic plants and algae. Phosphorus
compounds are found naturally in many types of
rocks. Mines in Florida and throughout the world
provide phosphorus for numerous agricultural and
industrial uses.
The Role of Phosphorus
in Waterbodies:
Like nitrogen, phosphorus is an essential
nutrient for the growth of all plants, including
aquatic plants and algae. Phosphorus in waterbodies
takes several forms, and the way it changes from
30








one form to another (called cycling) is complex.
Because phosphorus changes form so rapidly,
many aquatic scientists generally assess its avail-
ability by measuring the concentration of total
phosphorus rather than the concentration of any
single form. In some waterbodies, phosphorus may
be at low levels that limit further growth of aquatic
plants and/or algae. In this case, scientists say
phosphorus is the limiting nutrient.
For example, in waterbodies having TP concen-
trations less than 10 itg/L, waters will be nutrient
poor and will not support large quantities of
algae and aquatic plants.
There are many ways in which phosphorus
compounds enter waterbodies. The more com-
mon ones are described below:
* Some areas of Florida and other parts of the
world have extensive phosphate deposits. In
these areas, rivers and water seeping or flowing
underground can become phosphorus enriched
and may carry significant amounts of phospho-
rus into waterbodies.
* Sometimes phosphorus is added intentionally to
waterbodies to increase fish production by fertilizing
aquatic macrophyte and algal growth.


* Phosphorus can enter waterbodies inadvertently
as a result of human activities like landscape
fertilization, crop fertilization, wastewater disposal,
and stormwater run-off from residential
developments, roads, and commercial areas.

c See Algae, Limiting nutrient,
Phytoplankton, Total nitrogen,
Water clarity, and Water quality.


In Florida:
Waterbodies in the Florida LAKEWATCH
database analyzed prior to January 1998 had total
phosphorus concentrations which ranged from less
than 1 to over 1000 itg/L. Using these average
concentrations of total phosphorus from this same
database, Florida lakes were found to be distributed
into the four trophic states as follows:7
* approximately 42% of these lakes (those with
TP values less than 15 itg/L) would be classified
as oligotrophic;
* about 20% of these lakes (those with TP values
between 15 and 25 itg/L) would be classified as
mesotrophic;


Judging a lake by its label...
Although it's unreasonable to do so, the trophic state classification
of a waterbody is sometimes used as an indicator of "good" or -'
"bad" quality. For example, because oligotrophic waterbodies often
have very clear water, they are commonly characterized as being
"good." While typical eutrophic and hypereutrophic waterbodies,
with their pea soup green water and naturally weedy shorelines,
might be seen as being "bad."
Neither of these characterizations is necessarily fair; the
judgement of the quality of a waterbody should depend on how it is
going to be used. For instance, fish caught in supposedly "good"
oligotrophic waterbodies of Florida have some of the highest
concentrations of mercury in the state, making them potentially
"bad" sites for catching a fish dinner. Similarly, so-called "bad"
eutrophic and hypereutrophic waterbodies support some of
Florida's most abundant fish and bird populations, making them, in
reality, potentially "good" sites for fishing and birdwatching.
So, it's not sufficient to judge the quality of a waterbody by its
trophic state alone. Instead, one should consider what specific qualities are desirable or undesirable
based on how you intend to use the waterbody.

c* See Trophic state.








* 30% of these lakes (those with TP values
between 25 and 100 tig/L) would be classified as
eutrophic; and
* nearly 8% of these lakes (those with TP values
greater than 100 itg/L) would be classified as
hypereutrophic.

c- See Trophic state and each of its
categories: Oligotrophic, Mesotrophic,
Eutrophic, and Hypereutrophic; and
Water Quality.

The location of a waterbody has a strong
influence on its total phosphorus concentration. For
example, lakes in the New Hope Ridge/Greenhead
Slope lake region in northwestern Florida (in Wash-
ington, Bay, Calhoun, and Jackson Counties) tend to
have total phosphorus values below 5 tig/L. While
lakes in the Lakeland/Bone Valley Upland lake
region in central Florida (in Polk and Hillsborough
Counties) tend to have values above 120 tig/L.

c- See Lake region.

Health Concerns:
There is no known level of total phosphorus in
waterbodies that poses a direct threat to human health.

Transparency

c- See Water clarity.


Trophic state
is defined as "the degree of biological productivity
of a waterbody." Scientists debate exactly what is
meant by biological productivity, but it generally
relates to the amount of algae, aquatic macrophytes,
fish and wildlife a waterbody can produce and sustain.
Waterbodies are traditionally classified into
four groups according to their level of biological
productivity. The adjectives denoting each of these
trophic states, from the lowest productivity level to
the highest, are oligotrophic, mesotrophic,
eutrophic, and hypereutrophic.

7 This distribution of trophic state is based solely on total phosphorus
values without utilizing information on total nitrogen, water
clarity, or aquatic macrophyte abundance.


A bum rap...
Since waterbodies with low concentrations of
TP (total phosphorus) will have relatively clear
water, the public may think their water quality is
better than waterbodies with higher TP. It's a
misconception, however, that clearer water is
intrinisically better than water that is less clear.
Unfortunately, the association of clear water with
low phosphorus levels has given the public the
mistaken notion that phosphorus is a pollutant.


Aquatic scientists assess trophic state by using
measurements of one or more of the following:
* total phosphorus concentrations in the water;
* total nitrogen concentrations in the water;
* total chlorophyll concentrations a measure of
free-floating algae in the water column; and
* water clarity, measured using a Secchi disc; and
* aquatic plant abundance.
Florida LAKEWATCH professionals base
trophic state classifications primarily on the amount
of chlorophyll in water samples. Chlorophyll
concentrations have been selected by LAKE-
WATCH as the most direct indicators of biological
productivity, since the amount of algae actually
being produced in a waterbody is reflected in the
amount of chlorophyll present. In addition, Florida
LAKEWATCH professionals may modify their
chlorophyll-based classifications by taking the
aquatic macrophyte abundance into account.

c See Algae, Biological productivity,
Chlorophyll, Eutrophic, Hypereutrophic,
Mesotrophic, Nutrients, Oligotrophic, and
Trophic State Index (TSI).


32








Trophic State Index (TSI)
is a scale of numbers from 1 to 100 that can be used
to indicate the relative trophic state of a waterbody.
Low TSI values indicate lower levels of biological
productivity, and higher TSI values indicate higher
levels. The use of TSI is an attempt to make evalua-
tions of biological productivity easier to understand.
Using mathematical formulas, TSI values can
be calculated individually for four parameters: total
nitrogen concentrations, total phosphorus concen-
trations, total chlorophyll concentrations, and
Secchi depth. Sometimes a single TSI value for a
waterbody is calculated by combining selected
individual TSI values.
The State of Florida classifies waterbodies
according to "designated uses" that have been
assigned to each. (See Water Quality in this
circular for a more detailed description.)
The Florida Department of Environmental
Protection (FDEP) assesses water quality in
Florida by evaluating whether each waterbody is
able "to support its designated use." 8 The FDEP
assessment is based solely on TSI values as follows:
* waterbodies with TSI values from 0 to 59 are
rated as "good and fully support use;"
* those waterbodies with TSI values between 60 to
69 are rated as "fair and partially support use;" and
* waterbodies with TSI values from 70 to 100 are
rated as "poor and do not support use."
Individual TSI values may be further combined
in a special type of averaging to produce an
Average Trophic State Index (abbreviated TSIve).9
Government and regulatory agencies responsible
for water management often use the average value,
overlooking the fact that the designing author,
Dr. Robert Carlson of Kent State University in
Ohio, never intended TSI values to be reduced to
a single number. TSI values for individual
parameters could differ markedly within any
specific waterbody, and this significant variation
will be obscured when the TSI is calculated.
Dr. Carlson has noted that TSI values should
not be averaged; consideration of the differences in
individual TSI values in a waterbody can provide
insight and a better understanding of its biological
productivity.

33


Pitfalls of using TSI...
Applying words like good, fair, and poor to
TSI ranges has contributed to the
unfortunate misconception that trophic state
is synonymous with the concept of water
quality. While higher TSI values indicate
waterbodies with high levels of biological
productivity, this is not necessarily a "poor"
condition.
This can lead to evaluations that are
confusing. For example, consider a water-
body with a TSI of 80. Its high TSI rating tells
us that the lake has a high level of biological
productivity a capacity to support abundant
populations of fish and wildlife.
However, if we use Environmental Protec-
tion standards (see left column adjacent to this
text), the same TSI rating of 80 puts the
waterbody in the category described as "poor
and does not support use," regardless of the
fact that it is, in reality, able to support an
abundance of fish and wildlife. While this lake
may not be ideal for swimming or diving, it is
fully able to support recreational activities such
as fishing and bird watching.

c See Trophic state and Water Quality.


8The Florida Water Quality Assessment 305 (b) Report, 1996.
9 In Florida, the Secchi depth parameter is often not
incorporated into the TSI calculations because so many of
Florida's lakes are darkly colored waters. Also, the Florida
Department of Environmental Protection uses only the
measurements of total nitrogen and total phosphorus when
the concentration of total is not available .
If either of the nutrient concentrations is not available,
however, FDEP will not calculate the TSI.








The Florida LAKEWATCH Program does
not use the TSI system (neither the TSIave nor
individual TSI values). Instead LAKEWATCH
finds it more informative to use the individual
values of the four measured parameters without
transforming them into TSI values.

c- See Trophic State, Water Clarity,
and Water Quality.

Water clarity
is the transparency or clearness of water. While
many people tend to equate water clarity with
water quality, it's a misconception to do so.
Contrary to popular perceptions, crystal clear
water may contain pathogens or bacteria that
would make it harmful to drink or to swim in,
while pea-soup green water may be harmless.
Water clarity in a waterbody is commonly
measured by using an 8-inch diameter Secchi
disc, attached to a string/rope. The disc is lowered
into the water, and the depth at which it vanishes
from sight is measured. Measured in this way,
water clarity is primarily affected by three com-
ponents in the water:
* free-floating algae called phytoplankton,
* dissolved organic compounds that color the
water reddish or brown; and
* sediments suspended in the water, either stirred
up from the bottom or washed in from the shore.
Water clarity is important to individuals
who want the water in their swimming areas to

c See Algae, Humic acids, and Secchi depth.


be clear enough so that they can see where they
are going. In Canada, the government recommends
that water should be sufficiently clear so that a
Secchi disc is visible at a minimum depth of 1.2
meters (about 4 feet).
This recommendation is one reason that
many eutrophic and hypereutrophic lakes that
have abundant growths of free-floating algae do
not meet Canadian standards for swimming and
are deemed undesirable. It should be noted that
these lakes are not necessarily undesirable for
fishing nor are they necessarily polluted in the
sense of being contaminated by toxic substances.

c- See Trophic State.

The Role of Water Clarity
in Waterbodies:
Water clarity will have a direct influence on
the amount of biological production in a water-
body. When water is not clear, sunlight cannot
penetrate far and the growth of aquatic plants
will be limited. Consequently aquatic scientists
often use Secchi depth (along with total phosphorus,
total nitrogen, and total chlorophyll concentra-
tions) to determine a waterbody's trophic state.
Water clarity affects plant growth, but
conversely, the abundance of aquatic plants can
affect water clarity. Generally, increasing the
abundance of submersed aquatic plants to cover
50% or more of a waterbody's bottom may have
the effect of increasing the water clarity.
One explanation is that either submersed
macrophytes (plants), or perhaps algae attached
to aquatic macropyhtes, use the available nutri-
ents in the water, depriving the free-floating algae
of them. Another explanation is that the submersed
macrophytes anchor the nutrient-rich bottom
sediments in place buffering the action of wind,
waves, and human effects depriving the free-
floating algae of nutrients contained in the bottom
sediments that would otherwise be stirred up.
Because plants must have sunlight in order
to grow, water clarity is also directly related to
how deep underwater aquatic macrophytes will
be able to live. This depth can be estimated using
Secchi depth readings.


34








c( See Aquatic macrophytes, Algae,
Biological productivity, Chlorophyll, Color,
Particulates, Phytoplankton, Secchi depth,
Trophic state, and Water quality.

In Florida:
Waterbodies in the Florida LAKEWATCH
database analyzed prior to January 1998 had
Secchi depths ranging from less than 0.2 to over
11.6 meters (from about 0.7 to 38 feet).

r See Water quality.

The trophic state of a waterbody can be
strongly related to the water clarity. Using these
average Secchi depth readings from the Florida
LAKEWATCH database analyzed prior to
January 1998, Florida lakes were found to be
distributed into the four trophic states as follows:10
* approximately 7% of the lakes would be
classified as oligotrophic (those with Secchi
depths greater than 3.9 meters or about 13 feet);
* about 22% of the lakes would be classified as
mesotrophic (those with Secchi depths between
2.4 and 3.9 meters or between about 8 to 13 feet);
* 45% of the lakes would be classified as eutrophic
(those with Secchi depths between 0.9 and 2.4
meters or between about 3 to 8 feet); and
* 26% of the lakes would be classified as hyper-
eutrophic (those with Secchi depths less than 0.9
meters or about 3 feet).

cr See Trophic state and each of its categories:
Oligotrophic, Mesotrophic, Eutrophic, and
Hypereutrophic.


The location of a waterbody has a strong
influence on its water clarity. For example, lakes
in the New Hope Ridge/Greenhead Slope lake
region (Washington, Bay, Calhoun, and Jackson
Counties) tend to have Secchi depths greater
than 9 feet (3 meters). While lakes in the Lake-
land/Bone Valley Upland lake region (in Polk
and Hillsborough Counties) tend to have Secchi
depths less than 3 feet (0.9 meters).


r See Lake region.

Health Concerns:
Water clarity is not known to be directly
related to human health.

Water depth
is the measurement of the depth of a waterbody
from the surface to the bottom sediments. Water
depth can vary substantially within a waterbody
based on its morphology (shape). Florida LAKE-
WATCH volunteers measure water depth using a
weighted Secchi disk attached to a string or cord
that is marked in one -foot increments. The
weighted Secchi disk is dropped down until it hits
bottom and then the distance is determined by
measuring the length of rope between the bottom
and the surface of the water. These measurements
are then recorded for future reference.
Water depth can also be measured using a
device called a fathometer by bouncing sonic
pulses off the bottom and electronically calculating
the depth. Fathometer readings taken continuously
along a number of transects (shore-to-shore trips
across the waterbody) are used to calculate an average
lake depth. The calculated average lake depth is
approximately the same as the waterbody's average
water depth, called mean depth.

*r See Mean Depth, PVI (Percent Volume
Inf-\ ti,1 Ior Inhabited), PAC (Percent Area
Covered), and Submersed aquatic plants.


Water quality
is a subjective, judgmental term used to describe the
condition of a waterbody in relation to human needs or
values. The phrases "good water quality" or "poor
water quality" are often related to whether the water-
body is meeting expectations about how it can be used
and what the attitudes of the waterbody users are.
Water quality is not an absolute. One person
may judge a waterbody as being high quality, while

10 This distribution of trophic state is based solely on Secchi depth values
without utilizing information on nutrient concentrations,
concentrations or aquatic macrophyte abundance.


35




















someone with a different set of values may judge the
same waterbody as being poor quality. For example,
a lake with an abundance of aquatic macrophytes in
the water may not be inviting for swimmers but may
look like a good fishing spot to anglers.
Water quality guidelines for freshwaters have
been developed by various regulatory and govern-
mental agencies. For example, the Canadian Coun-
cil of Resource and Environmental Ministers
(CCREM) provides basic scientific information
about the effects of water quality parameters in
several categories, including raw water for drinking
water supply, recreational water quality and aes-
thetics, support of freshwater aquatic life, agricul-
tural uses, and industrial water supply.

c- See Recommended Reading
at the end of this circular.

Water quality guidelines developed by the
Florida Department of Environmental Protection
(FDEP) provide standards for the amounts of
some substances that can be discharged into
Florida waterbodies (Florida Administrative
Code 62.302.530). The FDEP guidelines provide
different standards for waterbodies in each of
five classes that are defined by their assigned
designated use as follows:
* Class I waters are for POTABLE WATER SUPPLIES;
* Class II waters are for SHELLFISH PROPAGATION OR
HARVESTING;
* Class III waters are for RECREATION, PROPAGATION
AND MAINTENANCE OF A HEALTHY, WELL-BALANCED
POPULATION OF FISH AND WILDLIFE;
* Class IV waters are for AGRICULTURAL WATER
SUPPLIES; and
* Class V waters are for NAVIGATION, UTILITY AND
INDUSTRIAL USE.


r See Biological productivity, Trophic state,
Trophic State Index (TSI), and Water clarity.


All Florida waterbodies are designated as
Class III unless they have been specifically classi-
fied otherwise (refer to Chapter 62-302.400, Florida
Administrative Code for a list of waterbodies that are
not Class III). Excerpts from the FDEP guidelines,
including some of the parameters measured by
Florida LAKEWATCH, are shown in the table on
page 37.

Watershed
is the area from which water flows into a water-
body. Drawing a line that connects the highest
points around a waterbody is one way to delineate
a watershed's boundary. A more accurate delin-
eation would also include areas that are drained
into a waterbody through underground pathways.
In Florida, these might include drainage pipes or
other man-made systems, seepage from high
water tables, and flow from springs. Activities in
a watershed, regardless of whether they are
natural or man-made, can affect the characteristics
of a waterbody.

Width of emergent and

floating-leaved zone (Average)
is an estimate of the average width (in meters or
feet) of the lake zone that is colonized by emer-
gent and floating-leaved plants. It's estimated
from the shoreline to the lakeward edge of the
plants.

See Emergent plants and Floating-
leaved aquatic plants.

In Florida:
Waterbodies in the Florida LAKEWATCH
database analyzed prior to January 1998, had
emergent and floating-leaved zone widths that
ranged from 0 meters to completely covering a
waterbody's surface. When waterbodies have
significant coverage by emergent and floating-
leaved plants, it would probably be more accurate
to call them deep water marshes, instead of lakes.
36















Parameter Standard Unit of Measure


Alkalinity Shall not be depressed below 20. mg/L as CaCO3



Chlorides No standard.


Conductance,
specific


Shall not be increased more than 50% above background
or to 1275, whichever is greater.


Nitrate No standard. ig/L



(a) nutrients The discharge of nutrients shall continue to be limited as needed to
prevent violations of other standards contained in this chapter. Man- ntg/L
induced nutrient enrichment (total nitrogen or total phosphorus) shall
be considered degradation in relation to the provisions of
Sections 62.302.300, 62-302,700 and 62.242, F.A.C.



(b) nutrients In no case shall nutrient concentrations of a body of water be altered so g/L
as to cause an imbalance in natural populations of aquatic
flora or fauna.


pH Shall not vary more than one unit above or below natural back-
ground or more than two-tenths unit above or below natural back-
ground of open waters, provided that the pH is not lowered to less
than 6 units or raised above 8.5 units. If natural background is less
than 6 units, the pH shall not vary below natural background or vary
more than one unit above natural background or more than two-
tenths unit above natural background of open waters.
If natural background is higher than 8.5 units, the pH shall not vary
above natural background or vary more than one unit below natural
background or more than two-tenths unit below natural background
of open waters.



Transparency Shall not be reduced by more than 10% as compared to the Depth of the
natural background values. compensation point
for photosynthetic
activity.





37
















Florida LAKEWATCH publications
are available by request. Call: 1-800-LAKEWATCH (1-800-525-3928).


* Florida LAKEWATCH Newsletters
containing educational articles on various topics are available on the Florida LAKEWATCH
web site at http://www.ifas.ufl.edu/~LAKEWATCH/index.htm or by contacting the
LAKEWATCH office and requesting a copy.

* Florida LAKEWATCH Data: What Does It All Mean?

* Florida Lake Regions: A Classification System

* Trophic State: A Waterbody's Ability to Support Plants, Fish, and Wildlife

* Information Circular 101: A Beginner's Guide to Water Management-The ABCs

* Information Circular 102: A Beginner's Guide to Water Management-Nutrients

+ Information Circular 103: A Beginner's Guide to Water Management-Water Clarity

Note: The circulars listed above are only the first three of a series; check with the
LAKEWATCH office or websitefor an updated listing.



Florida-specific Research and Information


Bachmann, M., M.V. Hoyer, and D.E. Canfield, Jr. 1999. Living at the Lake: A Handbook for Florida
Lakefront Property Owners. University of Florida, Institute of Food and Agricultural Sciences.
Publication SP 247.

Canfield, D.E. Jr., K.A. Langeland, M.J. Maceina, W.T. Haller, J.V. Shireman, and J.R. Jones. 1983.
Trophic state classification of lakes with aquatic macrophytes. Canadian Journal of Fisheries and
Aquatic Sciences. 40: 1713-1718.

Hoyer, M.V. and D.E. Canfield, Jr. 1994. Handbook of Common Freshwater Fish in Florida Lakes.
University of Florida, Institute of Food and Agricultural Sciences. Publication SP 160.

Hoyer, M.V., D.E. Canfield, Jr., C.A. Horsburgh, K. Brown. 1996. Florida Freshwater Plants. A Hand
book of Common Aquatic Plants in Florida Lakes. University of Florida, Institute of Food and
Agricultural Sciences. Publication SP 189.


38


Rm R n g *










Other Relevant Research and Information




Boyd, C.E. 1990. Water Quality in Ponds and Aquaculture. Auburn University, Auburn, Alabama.

Carlson, R.E. 1977. A trophic state index for lakes. Limnology and Oceanography. 22:361-369.

Carlson, R.E. 1979. A review of the philosophy and construction of trophic state indices. p. 1-52. [In] T.E.
Maloney (ed.). Lake and Reservoir Classification Systems. U.S. Environmental Protection
Agency. EPA 600/3-79-074.

Carlson, R.E. 1980. More complications in the chlorophyll-Secchi disk relationship. Limnology and
oceanography. 25:378-382.

Carlson, R.E. 1981. Using trophic state indices to examine the dynamics of eutrophication. p. 218-221.
[In] Proceedings of the international Symposium on Inland Waters and Lake Restoration. U.S.
Environmental Protection Agency. EPA 440/5-81-010.

Carlson, R.E. 1983. Discussion on "Using differences among Carlson's trophic state index values in
regional water quality assessment," by Richard A. Osgood. Water Resources Bulletin. 19:307-309.

Carlson, R.E. 1984. The trophic state concept: a lake management perspective. p.427-430. [In] Lake and
Reservoir Management: Proceedings of the Third Annual conference of the North American Lake
Management Society. U.S. Environmental Protection Agency. EPA 440/5-84-001.

Carlson, R.E. 1992. Expanding the trophic state concept to identify non-nutrient limited lakes and reservoirs. pp.
59-71 [In] Proceedings of a National Conference on Enhancing the States' Lake Management Programs.
Monitoring and Lake Impact Assessment. Chicago.

CCREM (Canadian Council of Resource and Environment Ministers). 1995. Canadian Water Quality Guidelines.
Prepared by the Task Force on Water Quality Guidelines of the Canadian Council of Resource and
Environment Ministers.

Chamberlin, T.C. 1890 (original printing); 1965 (reprinted). The Method of Multiple Working Hypotheses.
Science. 24: 754-758

Cooke, G.D., E.B. Welch, S.A. Peterson, and PR. Newroth. 1993. Restoration and Management of Lakes
and Reservoirs. Second edition. Lewis Publishers.

Forsberg, C. and S.O. Ryding, 1980. Eutrophication parameters and trophic state indices in 30 Swedish
waste-receiving lakes. Archiv fur Hydrobiologie 88: 189-207.

Ryding, S.O. and W Rast. 1989. The control of eutrophication of lakes and reservoirs. Man and the
Biosphere series, UNESCO, Paris. 314p.

Wetzel, R.G. 1983. Limnology. Second Edition. Saunders College Publishing.


39




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