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Lake water levels and trophic state variables in Florida lakes
Featured fish: redear sunfish
Featured bird: wood duck
Volunteer bulletin board
Lake water levels (cont.)
April showers may bring more than May flowers in Florida
Featured bird (cont.)
Deiae to Shrn Informatio About -.. Wae Maaemn an th Floid LAKE AT Prga Voum XX 00
Lake water levels and troi
variables in Florida lakes
Maurice Logan, LAKEWATCH sampler on Blue Lake in Polk County, started building a 5-sided, 9 foot high gazebo in 1989 which was well above the water level at the
start of its construction. Picture on left was taken in July 1989 when Blue Lake in Polk County was 2 feet above its lowest point in 39 years. The middle photo shows
Maurice standing on the floor of the gazebo without the water any where near the dock. The lowest water level of 103.38 feet above sea level was recorded by Mr.
Logan in 1982. But last year, with over 78 inches of rain, the water level rose. The current level of the lake is 119.36 feet above sea level-a difference of 16 feet. See
the picture on the right. The 5-sided gazebo is now sitting in a foot of water.
Rainfall either directly through
run off or indirectly through
increasing ground water is
the single greatest factor influencing
lake water levels. Lake levels can
fluctuate over the short term with
large storm events, annually with
seasonal rainfalls or over the long
term. During the last decade Florida
has experience extreme drought
conditions and tremendous rains
associated with hurricanes crossing
the state. During drought conditions
many lakes experienced all time low
water levels and some lakes even
dried completely. The rains from the
hurricanes then pushed many lakes
to all time high water levels causing
flooding in many areas.
The following are some affects
droughts have on lakes that are easy
SBoat access may be
hampered if not totally
Aquatic vegetation in the
lake can increase moving
toward open water areas
Aquatic bird abundance may
increase as shallow water
Muck areas may be
exposed to sunlight and
The following are some affects
high water levels have on lakes that
are easy to detect:
Boating areas may become
more available but more
hazardous because of
Tussocks and floating
vegetation may be floated
up into shallow areas to dry
Adjacent terrestrial and
wetland area may flood
causing increases in fish
Water color may increase
from runoff causing a
decrease in water
Because of these and other
affects, water level fluctuation is
often used as a lake management
tool for improving lake conditions.
However, what does all of this water
level fluctuation do to the water
chemistry of Florida lakes?
This question was recently
addressed by LAKEWATCH staff,
who examined long-term
LAKEWATCH water chemistry data
on 84 lakes that were also monitored
for water levels by Florida Water
Management Districts. This effort
culminated in a scientific publication
entitled "Lake Level and Trophic State
Variables Among a Population of
Florida Lakes and Within Individual
Lakes."* Continued on page 6.
Hoyer, M. V, C. A. Horsburgh, D. E. Canfe/d Jr.,
andR. W Bachmann 2005. Lake leveland rophic
state variables among a population of shallow
Florida lakes and within individuallakes. Canadian
Journalof Fisheries andAquatic Sciences. 62
I ne reaear sunnsn is iignt golden aDove witn ausKy grey spots or Dars on tne siae ana are wnite
light-colored edge on a black earflap, which is how it derives one of its common names-redear.
Te redear sunfish is a popular
sportfish in Florida because of
Sits food value and enjoyment
of catch. It is common throughout the
whole state of Florida. They are native
to the southeast extending north to
North Carolina in the east, to Indiana
and Missouri in the Midwest and west to
Oklahoma and Texas, but have been
transplanted outside the native area as
far north as Pennsylvania and northern
The redear sunfish is light golden
above with dusky grey spots or bars on
the side and are white to yellow/orange
below. They have a bright red or orange
spot with a light-colored edge on a black
earflap, which is how it derives one of its
common names-redear. The pectoral
fin is long and pointed and usually
extends far past the eye when bent
forward. They have a fairly pointed
snout with a small mouth.
Redear are found in ponds, swamps,
and lakes and vegetated pools with mud
or sand bottoms of small to medium
rivers. They are frequently found near
vegetation, stumps, logs and other cover.
They are occasionally found in brackish
Redear sunfish are opportunistic bottom
feeders feeding mainly during the daylight
hours on a variety of organisms including
algae, aquatic plants, zooplankton, and
aquatic and terrestrial insects. Redear also
use extensive flat top teeth in its throat to
crunch mollusk shells thus providing it with
another common name "shellcracker".
Redear spawn when water temperatures
reach 700F, usually April through August in
northern Florida and as early as March
through August in Central and South
Florida. They usually prefer water three to
four feet deep and a firm bottom. They will
frequently nest near water lilies,
maidencane and other emergent aquatic
vegetation. Males build and defend the nest
until larvae hatch often making grunting
noises during courtship. Females can lay up
to 30,000 eggs during a spawn.
Redear grow faster than other sunfish
and nine to ten inch redear are not
uncommon in Florida. They can live to over
eight years. The State record is 4 Ibs, 4oz
caught in Merritt's Mill Pond in 1986.
Redear are strong fighter but are
more difficult to catch than other
sunfish because they do not take
readily to artificial lures but prefer
natural baits. According to the Florida
Fish and Wildlife Conservation
Commission most redear in Florida
are taken on cane poles with small
hooks, corks and split shot for weight.
Redear meat is white and flaky and
In a study of 60 Florida lakes, redear
were found in 46 of the 60 lakes
sampled. These lakes ranged from 2
to 12,412 hectares in size and had an
average depth of 0.6 to 5.9 meters.
These lakes ranged from very weedy
(100% of the surface area covered in
aquatic plants) to very open (less than
1% of the surface area covered in
aquatic plants). The lakes were very
green (chlorophyll > 240 [ig/l) to very
clear (chlorophyll <1 igg/I). This
suggests that redear sunfish can
inhabit many diverse types of lakes in
( Ai sposI
A male :..:..3 ,. .3L ,,IC ir, r,,s nmu .11,...:.I.:.re.3 0 ,re i ,r,g plumI age The 1 .. :., : lors i.rl, I r:l de- ,r s.:-,er. ark gr, eer.'.-It
back and wings, chestnut breast and neck, green head, and white throat patch with white stripes forming a
complex pattern on the face and neck. There's even some maroon and purple coloation to tie everything together.
The wood duck is a distinctly North
American species and has as its only
close relative the Mandarin Duck, which
is found in eastern Asia. Other common
names for this species include woodie,
summer duck, acorn duck, swamp duck,
and squealer because of the squealing
alarm call they sometimes make when
startled. They prefer quiet undisturbed
woodlands, creeks, rivers, floodplains,
lakes, deciduous hardwood swamps, and
beaver ponds. When swimming in the
water, wood ducks are usually secretive
and make use of overhanging woody
vegetation as cover until approached
The wood duck is one of the most
beautiful ducks in North America. From
October through June is when the males
are in their most dazzling multi-colored
breeding plumage. The body colors
include iridescent dark green-blue back
and wings, chestnut breast and neck,
green head, and white throat patch with
white stripes forming a complex pattern
on the face and neck. They even have
some maroon and purple coloration to tie
everything together. Females have a
duller coloration consisting of a gray-
brown neck and head with a white
teardrop shaped eye-ring, white throat,
gray-brown breast stippled with white that
fades to a white belly, and a dark brown
back. On the wings, both males and
females have blue-green colored
speculums with a white rear borders.
Male wood ducks have red eyes and red
bills while females have brown eyes and
gray bills. Both sexes have long crests
that point downwards at the back of the
The wood duck is a medium sized
bird from 14 to 20 inches in length, with a
wingspan of 28 to 30 inches, and
weighing about 1 to 1.5 pounds. They
have short necks and long, square-
shaped tails. In flight, wood ducks tend to
keep their heads held above the level of
the body with their bills pointed down at
an angle. Because they have long and
relatively broad wings, they are agile
flyers and can easily weave in and out of
the tree canopies where they roost and
nest. Woodies also have sharp claws on
their webbed feet that help them perch on
tree limbs where they spend much of
their time when not swimming, feeding, or
flying. Although they share some habits
with dabbling ducks, they are considered
by experts to be members of the Tribe
Cairinini or perching ducks.
This species rides relatively high in
the water and feeds on the water's
surface similar to dabbling ducks. The
adult wood duck is mainly herbivorous
with plant materials making up about
90% of its diet. Important plant
materials include algae, watermeal,
water shield, duckweed, cypress
seeds, sedges, grasses, pondweeds,
mulberries, wild grapes, and acorns. In
some areas where it is grown, corn
may also be included in their diet.
The wood duck is widely
distributed in the United States where
it nests in areas east of the Mississippi
River, along the lower Missouri River
into South Dakota, in eastern Texas,
along the Pacific coast, and in the
southeastern coastal states. It winters
mainly along the Atlantic coast from
New York south, along the gulf coast
into central Texas, to the lower
Mississippi River valley and western
California. Some wood ducks winter in
Mexico south to the Distrito Federal.
Like other perching ducks, wood
ducks normally nest in tree cavities but
will accept artificial nest boxes.
Preferred nesting sites include trees
hollowed out by large woodpeckers
like the Pileated Woodpecker or hollow
logs and branches resulting from
broken limbs, lightning, fire scars,
heart rot, and logging operations.
Nests are located from 3 to 45 feet
above the ground in trees that are
greater than 16 inches in diameter.
Ideally the nests will be located near
water although sometimes they are
found up to half a mile from water. To
encourage nesting in artificial nest
boxes, wooden boxes should be
provided in open woods or on a pole in
standing water where the female can
see the nest box opening. Line the box
with sawdust to serve as a nesting
material because this species does not
carry nesting materials.
Females begin breeding when
one year old and line the nest with
down and fine feathers pulled from
their breasts. Nesting occurs from
March to July and after laying from 8
to 15 dull white eggs, the female will
incubate them for 28 to 35 days until
they hatch. If the weather is unusually
cold, or if the female is kept away from
Continued on page 8.
~v AC L' I I: I j: 1 -
In the past, many LAKEWATCH volunteers
have participated in the Secchi Dip-In. This project,
housed out of Kent State University in Ohio, helps
instill a sense of connection among all volunteer water
samplers throughout the world.
If you want to participate in this program this
year please go to their website (listed below) and
download a copy of the quiestionaire directly. All of the
data, including 2005 data, are now available on the
The Dip-In provides a national perspective of
water quality. It gives a comprehensive glimpse of
transparency at volunteer-monitored sites across the
United States, Canada and the rest of the world.
Scientists and volunteers can get a sense of how
transparency varies according to water type, regional
geology and land use. What is more important, these
annual Dip-In snapshots can be put together to form a
picture of changes in transparency over time.
If you want all of the information for your state,
please contact Bob Carlson via e-mail at
Dipin@kent.edu or call (330) 672-3992.
This year's Secchi Dip-In will take
place June 24 to July 16.
To download this year's questionnaire go to:
If you or someone you know is interested in joining the
LAKEWATCH team and help sample any of the
following lakes, please contact our office by calling
1-800-525-3928 or e-mail us at email@example.com.
Bradford County Lakes
Continued on page 8.
Thank you, Mr.
Logan, for shar-
ing your lake
The photos on the front
page were provided by
Maurice Logan of Blue Lake
located in Polk County. Mr. Logan has been recording
rainfall and lake levels in Blue Lake since mid-1967. You
may remember a past LAKEWATCH article that high-
lighted his lake level and rainfall data ("Where Does
Lake Water Come From?" in Volume XV on page 5).
His efforts deserve repeating!
Mr. Logan has documented that the water level
in Blue Lake is directly influenced by rainfall. He re-
corded the lowest levels (103.38 ft above sea level) in
1982 when the annual rainfall was only 31.89 inches.
He also recorded record high levels (119.36 ft above sea
level) last year with over 78 inches in annual rainfall. Mr.
Logan's has documented that Blue Lake has fluctuated
by as much as 16 feet over the last 39 years. WOW!
Maurice has also been an active LAKEWATCH
sampler since early 1991. He has collected 147 months
of LAKEWATCH data and he doesn't appear to be
slowing down. He just celebrated his 90th Birthday in
March-Happy Birthday Mr. Logan!
Update to the Lake Griffin Project
The University of Florida/Institute of Food
and Agricultural Sciences' Department of Fisheries
and Aquatic Sciences with funding from the Lake
County Water Authority is stocking Florida large-
mouth bass into Lake Griffin located in Lake
County. This is the second year of this project. All
fish stocked are tagged. Anyone catching a tagged
fish is asked to call our office and report where and
when they caught each fish along with the tag
number of the fish.
Thanks to all our Bass Anglers for calling in
the information. It is a crucial part of this project.
The ultimate end result is to improve the fishing on
Judging from the number of phones coming
in, this has been a successful project!
Good job LAKEWATCHers!
We thank all of you for taking the time to fill out and return the
mail list update information / questionnaire form from the last
newsletter. We received the biggest response thus far-literally
Thank you all!
/ To continue to receive the LAKEWA TCH newsletter you need to
f/il out the information form from the last LAKEWA TCH newslet-
ter (last page) and return it. Ifyou haven't returned your form
and still want to remain on our maii/g list please call us at I-
800-LAKEWA Tch (525-3928) so we can verify your mailing
S" Collection Center Update
In Citrus County, the TOOFAR office in Inverness will be modifing their office hours for the spring/
summer. They will be open Monday through Thursday from 10 am to 3 pm. The office will be closed
on Friday. The new hours will be in effect from Memorial Day through Labor Day.
Please make note of this change.
Greetings From the Water
Algae Filter Refresher Course
When folding your algae sample filters, please I
be sure to fold them exactly in half, with the
algae inside. Don't let any green algae show! If
any part of the algae sample is uncovered and
exposed while putting the filter into its wrapper,
some of it can rub off the sample filter and stick to the outside wrapper. That
portion of the algae is lost and the sample is less than accurate. You work hard to
collect these samples and we all want them to be the very best they can be. Thanks
for your help and keep up the good work!
No algae are n \ome algae are
Like this! Not like this!
Continued from page 1.
30 \ r = -0.85
17 18 19 20
30 r = 0.01
20 :. ":
41 42 43 4.
I I I
r = -0.01
I 1 5001 I
S10 11 17 18 19 2(
20 Little Weir
r = -0.62
16 17 18
r = -0.70
11 12 13
2 ,. :.****, .
15 16 17 18
42 43 44
Lake level (m MSL)
5 .. r = 0.82
4 17 18 19
2000 = 0.92 7.
0 9 10 11 12
Little Half Moon
15 _r =0.70
12 13 14 15
2- ." ".. -
26 27 28 29
26 27 28 29
Plots of total phosphorus (TP), total nitrogen (TN), and chlorophyll (Chl) concentrations and
Secchi depth (Secchi) versus corresponding monthly water levels for selected lakes (MSL, mean
sea level). Group -1 includes lakes with significant inverse relationships (about 25% of the lakes),
Group 0 includes lakes with no relationships (about 50% of the lakes), and Group 1 includes lakes
with direct relationships (about 25% of the lakes) between trophic state variables and lake levels.
So what does this mean for me?
The importance of this finding for LAKEWATCH volunteers is that it may be beneficial to monitor lake
water level along with their standard monthly water sampling. Determining if there is a relation between
lake water level and trophic state variables may help in future management activities for the lake.
Within the last year approximately 100 volunteers have begun to monitor lake levels. If any additional
volunteers would like to begin monitoring water levels on their lake contact your Regional Coordinator
at 1-800-LAKEWATch (525-3928) for information on how to get started.
The data were
analyzed and the
The results of this research
were somewhat surprising.
There were no holistic
relations between lake level
and lake trophic state
variables among all lakes.
Looking at individual lakes,
however, showed that
trophic state variables
decreased with increasing
water level in about 25% of
the lakes. A selection of
these lakes are displayed by
Group -1 in the graphs to the
left. Trophic state variables
increased with water level in
about 25% of the lakes. A
selection of these lakes are
displayed by Group 1 in the
graphs to the left. Finally,
trophic state variables
showed no real relation to
water level in about 50% of
the lakes. These lakes are
represented by Group 0
lakes in the graphs to the left.
The conclusion for these
findings suggest that
predicting how water levels
will impact trophic state
variables among a
population of lakes will be
difficult if not impossible and
that accurate prediction will
have to be made after first
individual lake systems.
Showers May Bring More 4 ,
May Flowers in Florida.../
traditional rainy season in Florida is between May and September. As much as we all
rain and in many circumstances look forward to the rainy season and the onset of Spring, the rain can
nted events. In the Florida LAKEWATCH Fish Kill Circular' data from canals located in the South Florida
t District were evaluated. Average rainfall for Florida's traditional rainy season (May through September)
of the annual average, whereas rainfall for the preceding four months accounted for only 18% of the
see the top figure below-the black line represents the rainfall average for each month in South Florida).
it same graph that a large majority (640%) of the fish kill events occurred between May and September
nts fish kill events for each month in South Florida canals).
ltly received a similar data set from the Florida Fish and Wildlife Conservation Commission. This data set
t are located in North Central Florida. There was a similar relationship in North Central lakes as was
orida canals between rainfall and fish kills. Average rainfall for this same time period accounted for 60% of
, whereas rainfall for the preceding four months accounted for only 250% of the annual average. The
kill events (60o) also occurred between May and September.
| Canals in South Florida
Lakes in North Central Florida
II--I : .I,
d above are a good example of how useful long-term data can be for making such compari-
ng evidence that many of the fish kills in Florida are related to rain events, particularly
.......sons. First, heavy rains tend to wash large amounts of organic matter such as dried
a canals, lakes, and ponds. As bacterial organisms begin to decompose the new material,
han normal. Secondly, cloudy skies decrease the amount of sunlight that the algae and
the Photosynthesis is the process that algae and plants produce oxygen. Since warm water
n cold water, the low levels of oxygen in the water caused by both of these scenarios is
ha'; y often occur when the water temperatures are warm. So, there is a potential for oxygen
t ter to get low enough to result in a summer fish kill under warm, cloudy, rainy weather-which,
cri a typical Florida summer."
t...n. v iie e "t ha cmany o th fise.h'3. kni -in F loid ar0e ra Fish Kills in Floridae
TCHllll p nfom n a ;'7 nr l:n3 cloudy I d Jcra's L e .. l able for downloadfrom our
Phtsntei is..... t o h g p p c e ee
Continued from page 4.
+ Access to lake experts around the state.
+ Quarterly and annual water chemisty
reports on the lake(s) of your choice.
+ Free quarterly newsletters and educa-
tional publications about lake ecology.
+ The knowledge that you are contributing
to the future of Florida's lakes.
This newsletter is generated by the Florida
LAKEWATCH program, within UF/IFAS' Department
of Fisheries and Aquatic Sciences. Support for the
LAKEWATCH program is provided by the Florida
Legislature, grants and donations. For more information
about LAKEWATCH, to inquire about volunteer training
sessions, or to submit materials for inclusion in this
publication, write or call:
PO Box 110600
Gainesville, FL 32611
All unsolicited articles, photographs, artwork or other
written material must include contributor's name,
address and phone number. Opinions expressed are
solely those of the individual contributor and do not
necessarily reflect the opinion or policy of the Florida
LAKEWATCH program. Inclusion does not constitute
endorsement, nor does exclusion represent censure of
any item, organization, individual, or institution by the
University of Florida or the Florida LAKEWATCH
Continued from page 3.
the nest for some reason, incubation may require a few extra days. The males
do not help with incubation.
The hen broods her newly hatched young for 24 hours before calling
them from the nest site. They respond with peeping calls and immediately
spring upward towards the -. ---.. .- ..
nest entrance, pausing ..--~. -..
momentarily before .
launching themselves s -
outward to the water or
land that is sometimes as
much as 60 feet below.
Surprisingly enough, they
usually land unhurt. If the
nest is located over land,
the clutch is quickly led to
water, which may take as
long as several hours.
Snapping turtles have been
known to take a heavy toll -
on the young as they learn -' i
how to swim.
The brood bonds .
break up after 5 weeks and -n-
the ducklings are fully Females have a duller coloration-a gray-brown neck and head
feathered and can fly at with a white teardrop shaped eye-ring, white throat, gray-brown
from 8 to 10 weeks of age. breast stippled with white that fades to a white belly, and a dark
brown back. Both males and females have blue-green colored
Ducklings require a high speculums with white rear borders on their wings. Pictured above
protein diet to fuel their are a female (in front) and male (in back) wood duck.
rapid growth so aquatic invertebrates such as dragonflies, aquatic insects and
their larvae, beetles, and spiders are eaten during the early weeks in their life
cycle. For successful recruitment into the adult population it is important that
these food sources be abundant where the young grow and develop.
Wood ducks have an amazing ability to return to the same breeding
area year after year. Sometimes several females will lay their eggs in one big
"dump" nest that can contain from 30 to 50 eggs! Although these dump nests
are sometimes abandoned, if they are successfully hatched and brooded they
can greatly increase production. Over much of the year, wood ducks occur in
pairs or small flocks of 4 to 15 birds, but hundreds may gather at fall and
winter roost sites.
Heavy hunting pressures and habitat destruction through the early
1900s nearly brought the wood duck to near extinction. The total closure of
wood duck hunting season from 1918 to 1941 along with habitat
manipulation, the creation of artificial nesting sites, and captive breeding
programs led to a rapid recovery in numbers over the following 20 years.
However, the wood duck is no longer common in the Central Valley. There are
now estimated to be well over 2 million wood ducks in North America. Another
threat has come from the introduction of European Starlings that invade
nesting cavities and displace the native birds like the wood duck.
The wood duck was a common species reported by Florida
LAKEWATCH bird survey participants. This species was observed on 36
different lakes located throughout Florida and sightings ranged from as few as
a single duck to as many as 44 ducks per survey. The average number of
wood ducks observed was about 6 birds per survey. Data reported by the
volunteers revealed that morning sightings were as likely as afternoon or
early evening sightings. Although wood ducks were reported for all 12 months
of the year, they were observed more frequently for the months of February
through June. This may be related to their breeding/brooding behavior
patterns where they may be more readily observed and localized.