Title: Biological and physical investigations of bodies of water beneath dense water hyacinth populations before and after chemical treatment /
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Title: Biological and physical investigations of bodies of water beneath dense water hyacinth populations before and after chemical treatment /
Physical Description: vi, 264 leaves : ill. ; 28 cm.
Language: English
Creator: Brower, William Wallace, 1948-
Publication Date: 1980
Copyright Date: 1980
 Subjects
Subject: Water hyacinth   ( lcsh )
Botany thesis Ph. D
Dissertations, Academic -- Botany -- UF
Genre: bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Thesis: Thesis--University of Florida.
Bibliography: Bibliography: leaves 261-262.
General Note: Typescript.
General Note: Vita.
Statement of Responsibility: by William W. Brower.
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Bibliographic ID: UF00098277
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: alephbibnum - 000099140
oclc - 06936482
notis - AAL4590

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BIOLOGICAL AND PHYSICAL INVESTIGATIONS OF BODIES
OF WATER BENEATH DENSE WATER HYACINTH
POPULATIONS BEFORE AND AFTER CHEMICAL TREATMENT










By

William W. Brower


A DISSERTATION PRESENTED TO THE GRADUATE COUNCIL OF
THE UNIVERSITY OF FLORIDA
IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE
DEGREE OF DOCTOR OF PHILOSOPHY










UNIVERSITY OF FLORIDA















ACKNOWLEDGEMENTS


The author would like to thank Dr. Joseph S. Davis for his

continued academic and research guidance, and Dr. William Haller

for his financial support and research guidance.

The author would also like to thank his loving wife, Sharon.

The completion of the author's education and this study would

have been impossible without her constant understanding, guidance,

financial support, and excellent typing.













TABLE OF CONTENTS


ACKNOWLEDGMENTS . . . . . . . . . .. . ii

ABSTRACT. . ... . . . . . . . ... . .. iv

INTRODUCTION . . . . . . . . . . . . .

PURPOSE . . . . . . . . ... . . . . . 3

MATERIALS AND METHODS .... . . . . . . .. 5

Descriptions of Study Area . . ... . . . . . 5
Field Sampling Procedure .. . . . . . . . 7
Chemical and Physical Measurements . . . . . . 13
Phytoplankton and Zooplankton Collection
and Counting . . . . . . . . ... . . 15
Periphyton Diatoms . . . . . . . . .. .17
Water Hyacinth Length. . . . . . . . . ... 20
Water Hyacinth Biomass . . . . . . . . . .
Sediment Accumulation. . . . . . . . . ... 21
Statistical Analysis . . . . . . . . . 21

RESULTS . . . . . . . . ... . . . . . . 25

Water Hyacinth Control . ... . . . . ... .25
Chemical and Physical Measurements . . . . . .. 42
Phytoplankton . . . . . . . . .. ..86
Zooplankton. . . . . . . . . .. . . .117
Periphyton Diatoms . . . . . . . . ... . 145
Water Hyacinth Length. . . . . . . . . . .235
Water Hyacinth Biomass . . . . . . . . .. .236
Sediment Accumulation. . . . . . . . . . .237

DISCUSSION. . . .. .. . . . . . . . . . 241

CONCLUSIONS .... . . . . . . . ....... .257

BIBLIOGRAPHY. .. . . . . . . . . ...... .260

BIOGRAPHICAL SKETCH . . . . . . .. . . . . 262











i l















Abstract of Dissertation Presented to the Graduate Council of
The University of Florida
in Partial Fulfillment of the Requirements for the
Degree of Doctor of Philosophy


BIOLOGICAL AND PHYSICAL INVESTIGATIONS OF BODIES
OF WATER BENEATH DENSE WATER HYACINTH
POPULATIONS BEFORE AND AFTER CHEMICAL TREATMENT


By


William W. Brower


August 1980


Chairman: Joseph S. Davis

Major Department: Botany


Dense infestations of water hyacinths (Eichhornia crassipes

Mart. Solms), or other free-floating, mat-forming aquatic weed

species, dramatically affect the water quality below them.

Dissolved oxygen concentrations, summer water temperatures,

the annual range of water temperature, and light penetration

are all reduced below actively growing hyacinth mats, while

suspended organic material, CO2, and HCO3 concentrations are

increased. Phytoplankton populations were fairly abundant

beneath actively growing hyacinth mats, and composed mostly

of blue-green algae (e.g. Oscillatoria limnnetica) and phyto-

planktonic diatoms (e.g. Fragilaria cacpucina var. mesolepta










and Melosira granulata var. angustissima). Under such conditions,

surface periphyton diatom populations were highly variable and

minimal while periphyton diatom densities at greater depths were

very low. Zooplankton populations were large, being composed

mostly of rhizopodal protozoans (such as Arcella spp. and

Centropyxis spp.), and also various rotifers and crustaceans.

Maximal hyacinth fresh weight biomass was found to be 57.7 kg/M

while the maximal dry weight biomass was 6.1 kg/M2

The hyacinth mats were chemically treated with 2,4-D,

which proved to be an efficient means of aquatic weed control.

After chemical treatment, floating mats of dying hyacinths were

persistent on the pond surfaces for several months. Water

quality under the decaying mats was worse than under actively

growing hyacinths. Phytoplankton and zooplankton populations

were much reduced while the periphyton diatom populations were

variable. The zooplankton was mostly composed of rhizopodal

protozoans which were feeding on the decaying vegetation.

Open water conditions were established approximately six

months after herbicide application, and water quality slowly

improved. Dissolved oxygen concentrations, pH, light pene-

tration, water temperatures, and annual range of water temper-

atures all increased, while CO2 and HCO3 concentrations, and

suspended organic material decreased. Phytoplankton populations

were large after hyacinth treatment and disappearance, being

mostly composed of blue-green algae, but with occasional large

seasonal green algae populations. Periphyton diatom populations









increased in both the pond surfaces and depths. Zooplankton

populations were reduced after open water conditions were

established and were largely composed of various rotifers and

crustaceans.

Sediment accumulation studies showed that the dry weight

of sediments deposited below actively growing hyacinths averaged

0.218 kg/M2 during an eight month period (3.6 percent of the

original hyacinth biomass available), while that below chemically

treated hyacinths was 0.626 kg/M2 (20.9 percent of original

biomass). Therefore, sedimentation was much greater (5.8 times)

after herbicide application to hyacinths. However, the majority

of the hyacinth biomass (79.1 percent) was not accounted for in

the sediments.















INTRODUCTION


The water hyacinth, Eichhornia crassipes Mart. Solms,

is a perennial, free-floating, mat-forming aquatic plant, which

often accumulates to form dense infestations in tropical and

subtropical areas (Holm et al. 1969).

The water hyacinth, an exotic species introduced into the

United States of America circa 1890, is native to South America.

Since its introduction, it has caused significant economic and

environmental impact on Southeastern U.S. waterways. According

to Penfound and Earle (1948), water hyacinths cause problems by

(1) obstructing navigation, (2) impeding drainage, (3) destroying

wildlife resources, (4) reducing water related recreation and

(5) constituting a hazard to life. However, perhaps the most

serious effect of dense water hyacinth infestations is their

environmental impact upon the water quality and species compo-

sition of aquatic ecosystems. It is well known that water

hyacinth infestations deteriorate water quality by reducing the

pH, dissolved oxygen concentrations, nutrient availability,

and light penetration of the underlying bodies of water (McVea

and Boyd, 1975). But what effect do water hyacinths have upon

the naturally occurring aquatic producer communities, which are

the basis for the entire aquatic food web? How are the phyto-

plankton and periphyton communities affected, and what effect










will this have upon the zooplankton communities? These are all

questions which have not been adequately investigated in the

past, and to which this study was partially addressed.

Control of aquatic weed populations has been thoroughly

investigated in the last several decades. Mechanical harvesting

of water hyacinths has been attempted time and time again, but

has proved uneconomical. These failures are due to several

factors, all of which continue to make mechanical harvesting

unfeasible on a large scale basis. Firstly, elaborate and

expensive harvesting machinery is needed. This machinery breaks

down often, is difficult and costly to repair, and requires

fairly skilled employees to operate. More importantly, aquatic

vegetation is composed mostly of water. Therefore, most of the

time and energy expended on mechanical harvesting is wasted on

moving water, not plant material.

During the last two decades there have been extensive

investigations into the use of various herbicide formulations

as a means to control chemically dense growths of aquatic

vegetation. This appears to be the most economically sound

means of aquatic weed control available at this time.

The most commonly used herbicide to control water hyacinths

is 2,4-D (2,4-Dichlorophenoxyacetic acid). This herbicide has

been successfully used for many years throughout the South-

eastern U.S., and especially Florida, where aquatic weed problems

can become quite severe. However, little emphasis has been placed

upon the in vivo conditions which arise due to herbicide application

and the effects that they have upon water quality and aquatic

biological communities.















PURPOSE


The objectives of this study were as follows:

1. Determine the effort required to eradicate water

hyacinths from small farm ponds using a herbicide

formulation of the oil soluble amine of 2,4-D

(Emulsamine E-3).

2. Study the aquatic biological communities (phyto-

plankton, periphyton diatoms, and zooplankton)

associated with naturally occurring dense infes-

tations of water hyacinths, populations of chemically

treated hyacinths, and those in open water conditions

after hyacinth treatment and disappearance.

3. Compare water quality parameters (chemical and

physical) associated with natural hyacinth pop-

ulations and open water conditions after hyacinth

treatment and disappearance.

4. Investigate the interrelationships and inter-

actions existing between aquatic producer (periphyton




Emulsamine E-3 is a registered product of Union Carbide
Agricultural Products Incorporated. Emulsamine E-3 contains
50.7 percent of the dodecyl and 12.7 percent of the tetradecyl
amine salts of 2,4-Dichlorophenoxyacetic acid. The product
is formulated as an oil soluble salt and contains 359.5 gm
acid equivalent per liter.










diatom and phytoplankton) and consumer (zooplankton)

communities, along with the physical and chemical

parameters which affect them.

5. Compare the environmental impact of herbicide

application to water hyacinths, to the impact

of naturally occurring populations of water

hyacinths on the aquatic environment.















MATERIALS AND METHODS


Description of Study Area


The three ponds studied are located in Silver Springs

Groves, a commercial citrus grove near Macintosh, Florida.

These three ponds are shallow bodies of water used for irri-

gation of the surrounding groves during dry periods and for

frost protection during cold weather. The ponds were constructed

in 1961. They originally had sand bottoms and clear water,

being fed by several small springs and ground water runoff.

Water hyacinths eventually invaded the area in the late 1960's,

and totally covered the surface of all three ponds (Fig. 1).

The ponds are highly eutrophic, receiving an abundance

of nutrients from springs and surface runoff of the fertilized

citrus groves. The once sand-bottomed ponds developed thick

deposits of dead and decaying organic material on the pond

bottoms which originated from naturally dying water hyacinths

and other vegetation. Water quality under these conditions

was poor. The water contained much suspended and dissolved

organic matter, little (if any) dissolved oxygen, abundant

nutrients, and smelled strongly of hydrogen sulfide.

The three ponds will be referred to as Ponds One, Two,

and Three, for convenience. All three ponds are interconnected,

with the highest ponds (Pond One and Pond Two, respectively)










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S 33 VI
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S44 One 4 04 4 q 4 4-













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< 0. 0. 0 Pond 0 /> <










Figure ap of Silver Springs Groves study area $
S = citrus trees, mixed hardw.



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feeding the lowest (Pond Three). Pond One is separated from Pond

Two by a dike, through which runs a 30 cm culvert that

allows water to flow from Pond One to Pond Two. Ponds Two and

Three are connected by a standpipe which allows overflow from

Pond Two to enter Pond Three. Overflow water from Pond Three

exits through a similar standpipe, and drains into a small creek

which eventually enters Orange Lake. Pond One has a surface

area of 0.81 hectares, with depths to a maximum of 1.5 M.

Pond Two is located between Ponds One and Three and is

the deepest of the three ponds, with depths up to a maximum

of 3.4 M and a surface area of 0.99 hectares.

Pond Three with a surface area of 1.87 hectares has a

fairly circular main body and a canal-like arm leading towards

Pond Two. Pond Three has a maximum depth of 2.0 M.



Field Sampling Procedure


The ponds were studied during a thirty-four month time

span from April 8, 1975, until January 18, 1978. Samples were

taken every three or four weeks throughout the study period,

except during a drawdown period (when the ponds were drained

to remove nutrient-rich water and to consolidate and oxidize

the sediments) in the summer and fall of 1976. Phytoplankton,

zooplankton, and periphyton diatom samples were taken during

each sampling period. Water samples and physical measurements

were obtained as often as possible.










Before herbicide application, all sampling had to be done

from a small jonboat towed across Ponds One and Two, or from

a dock built out into Pond Three, due to dense hyacinth popu-

lations. A rowboat was used for sample collection after open

water conditions were established,

The initial herbicide applications of 2,4-D were done by

professional field crews from the State of Florida Game and

Freshwater Fish Commission. Using an airboat and spraying

equipment, 2,4-D was applied to Ponds Two (Fig. 2) and Three

(Fig. 3) on May 15, 1975, at the rate of 3.34 kilograms of

active ingredient/hectare. Respraying was necessary two and six

months later (July 15, 1975, and November 19, 1975, respectively)

to insure complete control of hyacinths. Due to regrowth, these

ponds were resprayed after two months. At that time the pond

surfaces were covered with mats of organic detritus and dead

and dying hyacinths, many of which had started to reproduce

vegetatively by sprouting. After six months the hyacinth mats

were resprayed again, but by this time the mats only occupied

approximately one-fourth of the pond surfaces.

Ponds Two and Three were the experimental ponds treated

with 2,4-D, while Pond One was left untreated as an experimental

control for the first twelve months of the study. Pond One

was selected as the control pond since it is the highest pond,

and received no flow from either of the two experimental ponds.

Pond One was chemically treated with 2,4-D on April 15, 1976,

using the same procedures as on Ponds Two and Three. Efficient

























Figure 2. Pond Two during initial herbicide treatment on May 15, 1975.


























IL


























Figure 3. Pond Three during initial herbicide treatment on May 15, 1975.






























-
= '.1:


, r"Up


y3










hyacinth control was achieved with this first chemical treatment.

Retreatment (with Diquat) was not necessary until March 1977,

to control a marginal fringe of hyacinths, pennywort, and

duckweed.



Chemical and Physical Measurements


The determination of chemical parameters was done from

water samples collected during each field sampling. At least

two samples were collected from each pond at a depth of 30 cm

below the pond surface. Water samples were collected in clean,

airtight, dark polyethylene bottles, which were labeled and

immediately refrigerated in the field. Samples were transported

back to the lab where they were analyzed within 24 hours to

determine the following chemical parameter concentrations and

physical parameters: pH, HCO CO2, turbidity, soluble salts,

and specific conductivity. These samples were fixed with a

preservative (phenyl mercuric acetate), and later analyzed at

the University of Florida Soils Lab to determine the following

chemical parameter concentrations: nitrate-nitrogen, potassium,

total phosphate-phosphorus, available phosphate-phosphorus,

calcium and magnesium.

Turbidity was measured using a Hach turbidimeter, Model

2100A, measuring turbidity in Nephelometric Turbidity Units

(NTU's) which are equivalent to JTU's and FTU's. Specific

conductivity was determined by a YSI conductivity bridge,









Model 31, measuring specific conductivity in terms of micro-

mhos/cm The pH was measured with a Brinkmann pH meter,

Model PH-102.

Light penetration was determined by Secchi disk disappearance

and by a light meter. The Secchi disk used was 25 cm in diameter,

and divided into four alternating black and white quadrants.

The light meter (a LI-COR Model LI-185 Quantum/Radiometer/

Photometer) was equipped with a quantum type light probe

(Lambda Instrument Corp.), which measures quanta in the photo-

synthetically active radiation spectrum between 400 and 700
-2 -1
nannometers in microeinsteins M sec

The photosynthetic response of plants for which data are

available approximates this 400 to 700 nannometer range.

Readings obtained from this light meter must be multiplied by

1.40 when used in water to correct for the immersion effect

(since the light entering the diffuser scatters in all directions).

Light penetration readings using the quantum sensor were made

at 10 cm depth intervals throughout the water column, and also

above the water surface at different levels within the plant

cover (when present).

Visual estimates of the percentage of pond surface area

covered by water hyacinths, pennywort (Hydrocotyle spp.), and

duckweed (Lemna spp.), were made on each sampling date. These

estimates, when added together, approximate the total percentage

of pond surface areas covered by floating aquatic vegetation.









Phytoplankton and Zooplankton Collection and Counting


Surface quantitative phytoplankton and zooplankton samples

were collected on most sampling dates from the deepest accessible

portion of each pond. These quantitative samples were obtained

by pouring measured amounts of surface pond water through a

plankton net (#25-standard nylon with 83 meshes/cm). Precautions

were taken to insure that all of the plankton poured into the

net was collected in the tube attached to the bottom of the net.

This was done by lowering the net into the water (leaving the

mouth of the net above water), and then letting the water drain

out several times.

Immediately after collection, all phytoplankton and zoo-

plankton samples were labeled and preserved with 10 percent

formalin. Rose bengal solution (prepared according to Standard

Methods, 1965) was added to the samples to facilitate the counting

of zooplankters, especially rotifers and crustaceans.

The phytoplankton samples were thoroughly mixed before

counting. A subsample was removed with a Pasteur pipette and

placed into a Palmer counting cell. Phytoplankton was then

counted using a binocular microscope at a magnification of 312X.

Ten to fifty random fields within the Palmer cell were then

counted. The number of fields counted depended on the density

of phytoplankton within the sample.

Phytoplankters were counted and identified to genus, and

to species when possible. This identification was facilitated

by G.W. Prescott's Algae of the Western Great Lakes Area (1962),









and Whitford and Schumacher's Fresh-Water Algae in North Carolina

(1969). Planktonic diatoms were usually identified only to

genus (unless the species names were obvious), since the diatom

samples were not "cleaned" to aid in identification. These plank-

tonic species were usually similar to the members of the peri-

phytonic diatom populations.

The average number of the individual phytoplankters per

field and total phytoplankton were calculated. Phytoplankters

were counted and recorded in terms of cells per liter of original

pond water. Whole colonies and broken colonies (Microcystis,

Volvox, Eudorina, Synura, Dinobryon, etc.) were observed and

counted in terms of individual cells to determine an average

number of cells per colony. This average was then used to

convert from colonies to individual cells per liter.

Zooplankton samples were similarly counted in a Sedgewick-

Rafter Counting Cell at a magnification of 156X. Zooplankton

included protozoans, rotifers, rotifer larvae, crustaceans,

crustacean larvae, and crustacean eggs. Colonial forms were

counted in terms of individuals. The total zooplankton counts

were in terms of total zooplankton individuals per liter of

original pond water.

Zooplankters were usually identified only to genus, except

in the case of certain cosmopolitan rotifers and crustaceans

which were identified to species. This identification was

aided by Ward and Whipple's Freshwater Biology (1959).

The Sedgewick-Rafter counting cell serves for counting

and estimating population sizes of microzooplankton (e.g.










rotifers, protozoans, nauplii larvae), but biases the estimations

of macrozooplankton (e.g. Cyclops, Diaptomus, chironomids)

populations. For this reason, macrozooplankton was also determined

on the basis of individuals per liter of original pond water.

These macrozooplankton counting wheel determinations were found

to be more realistic than counts made with the Sedgewick-Rafter

counting cell when used for macrozooplankters. All zooplankters

larger than nauplii larvae are reported in terms of the counting

wheel population estimations, while nauplii larvae and smaller

organisms are reported in terms of the Sedgewick-Rafter counting

cell population estimations.



Periphyton Diatoms


Periphyton diatoms were collected on artificial substrate

by using diatometers (Biomonitor Inc., Ripon, Wisconsin) containing

glass microscope slides. These diatometers are plastic frames

each holding eight glass slides which are held in place by a

wire frame with attached styrofoam floats. The glass slides

are held in a vertical position in the water column and are

exposed to the water and available sunlight. The floats keep

the submerged diatometers in a horizontal position. The slides

within remain vertical to reduce sediment accumulation, which

would bury attached diatoms.

Diatometers were installed in each of the three ponds

on April 22, 1975. Surface and one meter depth diatometers

were placed in Ponds One and Three, while Pond Two (the deepest)









received surface, one meter and two meter depth diatometers.

The diatometers were secured by weights to the pond bottoms.

Slides were exposed to the water column for periods of

three or four weeks, after which time they were removed and

clean slides reinserted. Removed slides were then labeled

and allowed to air-dry. No special preserving technique was

necessary for such dried slides since the siliceous frustules

of diatoms will not desiccate or deteriorate in air. Slides

so obtained can be stored indefinitely.



Periphyton Diatom Density Counts


Diatom density counts were made to estimate the total number

of diatom valves per cm in the three ponds (surface and depths)

throughout the study period. This was done by counting all the

diatom valves observed in a vertical strip 2.54 cm long and 46

microns wide down a dried slide from the diatometers. The

several density counts obtained for each sample were averaged

and numerically converted to diatom valve density per cm of

artificial substrate.



Periphyton Diatom Slide Preparation


The diatoms on one of the dried diatom slides from each

collection were "cleaned" to oxidize all organic matter. This

organic matter, if not removed, would interfere with the

identification of the diatoms. "Cleaning" (Van der Werff,

1958) was accomplished by adding 100 ml of 30 percent H202










to the air-dried diatometer slide in a 1000 ml beaker. The

slide was allowed to remain in this solution for 24-48 hours.

A small amount of K2Cr207 was then added to the beaker initiating

an exothermic reaction. After the boiling subsided, this solution

was poured into a 200 ml beaker which was then filled to the

top with distilled water. After four hours, the top 150 ml

of solution in the beaker was decanted. The beaker was then

refilled with distilled water. This step was repeated until

the solution in the beaker became colorless, indicating that

the K2Cr207 was now absent from the solution and the diatoms

were ready to mount on slides.

The cleaned samples were then pipetted onto coverslips,

using clean Pasteur pipettes and allowed to air dry. This

process was repeated until visual observation indicated an

adequate accumulation of diatom frustules on the coverslips.

Microscopic investigation of the coverslips was necessary to

determine whether enough diatoms were on the coverslips, especially

in samples where sand or other siliceous deposits were present.

The remaining cleaned diatom mixture left over after making the

slides was put into vials and stored for future reference.

After they were air-dried, the coverslips were placed diatom-

side up on a hot plate, and heated at approximately 5400C for

30 minutes to evaporate moisture and to oxidize any remaining

organic matter. After 30 minutes, slides were removed from the

hot plate with forceps and inverted onto a drop of Hyrax mounting

medium on a clean glass slide. The slide (with coverslip and









Hyrax) was then placed on the hot plate to drive the solvent

from the Hyrax. The slides were then removed from the hot plate

and labeled.



Diatom Species Proportional Analysis


The prepared diatom slides were then examined to obtain

a species proportional analysis of the diatom populations in-

habiting the three ponds throughout the sampling period. This

was done by counting 200 diatom valves per slide, and at least

100 valves on those slides which were thinly populated with diatoms.

Counting and identification of the diatom valves was done under

the oil immersion objective (1162.5 magnifications). Identi-

fication was aided by several taxonomic keys such as Patrick

and Reimer (1966) and Hustedt (1930).



Water Hyacinth Length


The length (meters) of water hyacinths was measured in

Pond One (control pond) and Pond Two (treatment pond) for the

first three months of the study (April 8, 1975, to June 29,

1975). The length of hyacinth plants was measured in situ,

from petiole tips to root tips. Several such measurements were

similarly obtained from each pond and averaged.









Sediment Accumulation


The investigation of sediment accumulation beneath actively

growing hyacinth populations, and chemically treated populations

was not a prime objective of this study, but an attempt was

made to study this phenomenon.

Submerged pans, each with an exposed surface area of
2
0.09 M2, were suspended from buoys in Ponds One and Two, one

meter below the pond surfaces. Two sediment pans were placed

in Pond One (control pond), and three in Pond Two (treatment

pond). These sediment pans were placed in the ponds on May

14, 1975, before herbicide application, and carefully removed

on January 12, 1976, after all floating debris had disappeared.

The sediment-water slurry taken from the pans was then

filtered to separate the organic material from the water. This

organic material was then dried in an oven at 600C for 48 hours

and the dry weight determined.



Statistical Analysis


The data of this study were statistically analyzed using

the facilities of the Northeast Regional Data Center located

on the University of Florida Campus in Gainesville, Florida.

The procedures and programs of SAS 76-78 (Statistical Analysis

System) were used to sort and analyze all data.

Correlation coefficients were determined between all variables

using the SAS CORR procedure. This procedure determines the

correlation coefficient between two variables and approximates









the significance probability of the correlation coefficient.

The significance probability of a correlation coefficient is the

probability that a value of the correlation coefficient as

large or larger in absolute value than the one calculated would

have arisen by chance, if the two random variables were truly

uncorrelated (Barr et al. 1976).

Only those correlations which had a significance probability

of 10 percent or less are reported and are noted as being either

positively or negatively correlated.

The SAS STEPWISE procedure was then used to determine which

of the collection of independent variables that showed significant

correlations should most likely be included in a regression model.

This procedure is useful for determining the relative strengths

of the relationships between proposed independent variables and

a dependent variable and involves the use of stepwise multiple

regressions.

This procedure first finds the single-variable model which

produces the largest R2 statistic (R2 is the square of the

multiple correlation coefficient). For each of the other

independent variables, STEPWISE calculates an F-statistic

reflecting that variable's contribution to the model, if it

were to be included. If the F-statistic for one or more variables

has a significance probability greater than the specified

"significance level for entry" (50 percent in this study), then

the variable with the largest F-statistic is included in the

model. In this way, variables may be added one by one to

the model. However, after a variable is added, STEPWISE looks










at all the variables already included in the model. Any variable

no longer producing a parial F-statistic significant at the

specified significance level for staying in the model (50 percent)

is then deleted from the model. Only after this check is made

and any required deletions accomplished, can another variable

be added to the model (after F-statistics are again calculated

for the variables still remaining outside the model, and the

evaluation process is repeated). Variables are thus added one

by one to the model until no variable produces a significant

F-statistic. The process terminates when no variable meets the

conditions for inclusion in the model, or when the variable to

be added to the model is one just deleted from it (Barr et al.

1976). The previously described procedure includes the STEPWISE

option of the STEPWISE procedure.

Using the above mentioned statistical procedures, the best

possible models for specific parameters were determined from lists

of selected independent variables until the largest variance in

the dependent variable was accounted for. The lists of independent

variables from which the STEPWISE procedure selected the best

possible regression models were as follows:

A. Total phytoplankton and phytoplankters: pH, bicarbonate,

turbidity, soluble salts, potassium, available phosphate-

phosphorous, calcium, magnesium, specific conductivity,

water temperature, percent total vegetation cover,

Secchi disk disappearance, light penetration, and

nitrate-nitrogen.









B. Total zooplankton, zooplankters, etc.: percent total

vegetation cover, water temperature, dissolved oxygen,

pH, and total phytoplankton.

C. Periphyton diatoms, etc.: pH, bicarbonate, turbidity,

soluble salts, potassium, available phosphate-

phosphorous, calcium, magnesium, specific conductivity,

water temperature, percent total vegetation cover,

Secchi disk disappearance, light penetration, nitrate-

nitrogen, and total phytoplankton.

Only those models which showed a significance probability

of 10 percent or less are reported in this study.















RESULTS


Water Hyacinth Control


The application of 2,4-D by airboat spray crews to dense

growths of water hyacinths proved to be a very efficient means

of control. The hyacinth plants began to wither and curl

within hours after herbicide application to Ponds Two and Three

on May 15, 1975. A swathlike pattern of dying hyacinths was

visible within three days after treatment (Fig. 4). This swath

pattern is typically found after airboat application of herbicides

to dense growths of water hyacinths due to propeller dispersion.

A thick cover of decaying water hyacinths remained on the

surface of the treatment ponds six weeks after treatment (June

29, 1975), with approximately 75 percent of the plants dead.

However, many small patches of live juvenile and seedling plants

were present and the underwater portions of many apparently

dead plants were still green and viable. Sprouting (vegetative

reproduction) of new small plants was also occurring from many

of the old "dead" plants.

At this time it was apparent that respraying of the treatment

ponds was necessary even though the initial treatments had

been effective (75 percent control). If respraying had not

been done soon, undesirable regrowth would have eventually


























Figure 4. Pond Two one week after initial herbicide treatment on
May 22, 1975, showing swathlike pattern of dying hyacinths.






















a









resulted in complete pond coverage. Retreatment took place on

July 15, 1975. Herbicide application was much simpler and more

thorough, due to the increased maneuverability of the airboat

through the dead hyacinth mats.

During September 1975, four months after the initial

treatment, the majority of hyacinths were dead, forming large

floating mats of decaying organic material. Such floating

mats are commonly referred to as "sudds" (Fig. 5). During

this time foul water conditions existed which included strong

H2S odors, very little dissolved oxygen, an abundance of floating

and suspended organic material in the water, and dark brownish-

gray colored water. During this period water quality was even

worse than that occurring under actively growing hyacinth mats.

Prevailing winds often swept the sudds across the pond surfaces,

from end to end. Various grasses, sedges, and other plants

had colonized these sudds by October and November of 1975.

These floating mats of organic material (sudds) had dis-

appeared by December 1975, six months after the initial treatment.

This cleared most of the pond surfaces, leaving open water con-

ditions (Fig. 6). The remaining plants included a minimal

surrounding marginal fringe of pennywort (another surface mat-

forming species) and water hyacinths. These fringes were

retreated with 2,4-D as before.

This retreatment of the marginal hyacinth and pennywort fringe

with 2,4-D killed almost all of the water hyacinths but had little

effect upon the pennywort population. This pennywort fringe re-

mained viable in several large patches, but was dormant during winter.
























Figure 5. Pond Two four months after initial herbicide treatment,
and two months after retreatment. Floating mats
of organic material ("sudds") are found on the pond surface.



































~~- c






A0
40


























Figure 6. Pond Two in April 1976, after open water conditions have
been established (before pond drawdown).







6~ ?









The pennywort fringe, which began actively growing in

early spring, was sprayed in March and April of 1976 with

Silvex (2,4 Trichloropropionic acid) according to label instruc-

tions with a portable sprayer operated from a sixteen foot

jonboat. This final spraying killed and controlled the marginal

fringes. Marginal fringes reappeared at times, but they did

not constitute a major problem in either treatment pond during

the remainder of the study.

Although herbicide application controlled the water hyacinths

and pennywort, other aquatic weeds appeared in the treatment

ponds. Duckweed had always been present in all three ponds

occurring in small numbers among the members of the actively

growing hyacinth and pennywort communities. Treatment of the

mat-forming species permitted duckweed to eventually dominate

the pond surfaces (treatment Ponds Two and Three). Heavy

phytoplankton blooms were also prevalent during this time.

Duckweed was first noticed on Pond Two in May and June 1976,

and by the end of July 1976, covered most of the pond surface

area.

Most likely, the control of the duckweed populations could

have easily been achieved using herbicide application but this

was not done for two reasons. Firstly, the duckweed was being

harvested in rather small amounts (a pickup truckload from time

to time) to feed experimental populations of the aquatic weed

eating fish, the white amur (Ctenopharyngodon idella Val.),

which were being grown at a different location. Secondly,









the effect of duckweed mats on water quality could be inves-

tigated. The duckweed populations disappeared when the pond

drawdowns occurred.

A drawdown of Ponds Two and Three was started on June 20,

1976. The water level in Pond Three dropped quickly. The pond

was almost drained by July 18, 1976. Pond Two drained more

slowly, and was only down one meter on September 28, 1976.

Pond Two was totally drained by October 1976.

The water levels in the treatment ponds were drawn down

during this study to remove the nutrient-rich water contained

in the ponds after chemically treating the aquatic vegetation,

to consolidate and oxidize the abundant sediments on the pond

bottoms, and to study sediment thickness and nutrient composition

in conjunction with another study.

Before the ponds were totally drained, 2.0 ppm of Rotenone

was added to kill all the fish living in the remaining water

of each pond. No fish were found in either treatment pond.

The water levels in Ponds Two and Three were re-established

in January 1977, by which time the sediments in both ponds

had consolidated significantly (Fig. 7). During the remainder

of the study period, only small marginal fringes of hyacinths,

pennywort, alligatorweed (Alternanthera philoxeroides), and

duckweed appeared in the treatment ponds. These small marginal

fringes occasionally arose, but were easily controlled by herbicide

application from a hand sprayer or by manual removal.

Pond One was left untreated (as a control) for the first

twelve months of the study so that comparisons between actively


























Figure 7. Pond Three in January 1978, after open water conditions
have been established following pond drawdown.

































































































































































































































..............



















.................













...........













.................. ...... .....

........ .. ........









growing hyacinth and chemically treated hyacinth ponds could

be made (Fig. 8). However, on April 15, 1976, Pond One was

treated with 2,4-D as Ponds Two and Three had been treated one

year before. Thus, Pond One acted as an experimental control

pond during year one of the study, and then as another experimental

treatment pond (lagging one year behind Ponds Two and Three).

Treatment of hyacinths in Pond One showed the same results as in

the treatment of Ponds Two and Three. Hyacinth control was con-

siderable after three to four weeks. Very efficient control

was evident after six to eight weeks. After nine weeks (June

23, 1976) foul water conditions existed, with stong H2S odors,

and floating or suspended organic matter in the water. The

water was a cloudy brownish-gray color, and contained little

dissolved oxygen. Herbicide treatment of hyacinths does not

create foul water conditions, for such water quality conditions

are also commonly found beneath actively growing hyacinth popu-

lations, before herbicide treatment. However, herbicide treatment

does temporarily worsen water quality.

In Pond One, approximately 70 percent of the hyacinths

were controlled by the middle of July 1976. Pond One was re-

treated on July 15, 1976, to control the remaining hyacinths,

which were beginning to vegetatively reproduce (Fig. 9). The

large decaying, floating mats of organic material (sudds) remain-

ing after hyacinth control supported populations of pennywort and

various grasses. These decaying mats (being similar to those

found in Ponds Two and Three) persisted through October, after


























Figure 8. Pond One (control pond) in April 1975, showing intact,
untreated floating mats of aquatic vegetation.
















C r
























Figure 9. Pond One (control pond) on July 15, 1976, during herbicide retreatment.







1.









which time they had all eventually broken up, and aerobically

oxidized or sunk. Pond One then had open water conditions

except for a large marginal fringe of hyacinths, pennywort,

and duckweed.

This fringe was sprayed with Diquat (Chevron Chemical

Co.) according to label instructions in March 1977. This

spraying controlled most of the marginal fringe but did not erad-

icate it. A small fringe (one to three feet in width) grew

back during early summer, and was prevalent during the rest

of that season.

In general, the treatment of Ponds One, Two, and Three

showed that very dense infestations of water hyacinths can be

controlled (75 to 90 percent control is fairly easy to achieve),

and eventually eradicated by chemical treatment. However, under

high nutrient conditions (such as in these citrus ponds), regrowth

and the appearance of other aquatic weed infestations can be

expected. Only by monthly monitoring, and occasional herbicide

applications or hand removal of fringe or regrowing plants, can

control of floating aquatic plant populations be achieved under

such conditions.



Chemical and Physical Measurements


Hydrogen Ion Concentration (pH)


The pH during the study period ranged from 6.20 to 9.04

in Pond One, 6.20 to 9.30 in Pond Two, and 6.00 to 9.80 in

Pond Three (Fig. 10). The lowest pH's (6.0 to 7.3) were found









10.0 +
I 3i
9.5 t


9.o / \ '

SI
S8.5 + / I *
H "/ / I ,


S i / \

7.5 + :






A J A NMAM AS NA M JD F





DAI TE
'A M J J A S O N D "J F M A M J J A S O N D" J F M A M J J A S O N D J F
1975 1976 1977


Figure 10. Citrus Ponds surface pH
(- = Pond One, ---= Pond Two, *....... Pond Three).









under actively growing, or dying hyacinth mats, due to the high

levels of CO2 found during these periods. Higher pH's (7.3 to

9.8) occurred after disappearance of the hyacinth mats (open

water conditions), while CO2 concentrations were lower. After

hyacinth disappearance, higher pH's occurred during spring and

summer, while lower pH's occurred during fall and winter.



Bicarbonate (HCO,)


The concentration of bicarbonate ion (HCO ) during the

study period ranged from 33.4 to 89.2 ppm in Pond One, 37.3

to 104.6 ppm in Pond Two, and from 5.8 to 95.7 ppm in Pond

Three (Fig. 11). In general, the concentration of HCO was

higher under actively growing or dying hyacinth mats, and

lower after hyacinth disappearance (open water conditions).

Higher HCO concentrations were found during summer, while

lower concnetrations occurred during winter.



Carbon Dioxide (CO2)


The concentration of carbon dioxide (CO2) during the

study period ranged from 0.7 to 47.8 ppm in Pond One, 1.2 to 34.7

ppm in Pond Two, and from 0.2 to 39.0 ppm in Pond Three (Fig. 12).

The concentration of CO2 was high under actively growing or

dying hyacinth mats (18 to 48 ppm), when respiration far exceeded













128


1975 1976 1977

DATL

Figure 11. Citrus Ponds surface bicarbonate ion concentrations in ppm
( = Pond One, - = Pond Two, ....... = Pond Three).













I
40 +



42 +


36 +



30 +



24 +



18 +



12 +



6 +



0 +


DA E


Figure 12. Citrus Ponds surface carbon dioxide concentrations in ppm
(-- = Pond One, ---= Pond Two, **......= Pond Three).









photosynthesis due to decomposition and lack of light. The con-

centration of CO2 was low after hyacinth disappearance (10 ppm

or less), when photosynthesis had increased, and equalled or

exceeded respiration.



Turbidity


Turbidity readings ranged from 2.4 to 55.5 NTU's in Pond

One, 1.6 to 130.0 NTU's in Pond Two, and from 1.2 to 106.8 NTU's

in Pond Three (Fig. 13). Turbidity readings decreased in the

years after hyacinth treatment. Turbidities were largest during

warm water periods, and smallest during cool water periods.

Turbidities increased during hyacinth treatment and while the

hyacinth populations were dying in Ponds Two and Three.



Soluble Salts


The concentration of soluble salts during the study period

ranged from 142.5 to 324.5 ppm in Pond One, 138.0 to 397.0 ppm

in Pond Two, and from 160.0 to 409.0 ppm in Pond Three (Fig. 14).

Soluble salts were lowest under actively growing hyacinth pop-

ulations and highest in the years following hyacinth disappearance.



Specific Conductivity


Specific conductivity determinations were only done after

herbicide treatment of the ponds. The specific conductivity of
Pond One ranged fro 301.0 to 4055 micromos/cm, 2 0 o 39
Pond One ranged from 301.0 to 405.5 micromhos/cm 275.0 to 397.0










144 +


126 +


108 +


90 +


72 +


54 +


36

18 I


0 +


1975 1976 1977

DA TF


Figure 13.


Citrus Ponds surface turbidity in nephalometric turbidity units
(--- = Pond One, ---= Pond Two, .......= Pond Three).













380 A






205 1 .1-3r ----
345

310 '

P
P 275
M
... 3 .... i .......... .



205 3/ 3-


170 +


135 +
*A MJ JASO N D J F M A M i J A S 0 ND J F MA M J 5 OND
1975 1976 1977

DA TE
Figure 14. Citrus Ponds surface soluble salts concentrations in ppm
(--- = Pond One, --- = Pond Two, *.......= Pond Three).










micromhos/cm2 in Pond Two, and from 230.0 to 409.0 micromhos/cm2

in Pond Three (Fig. 15). In general, the highest specific con-

ductivities were found after hyacinth disappearance, and after

open water conditions had become firmly established, when nutrients

liberated from decomposing hyacinths were abundant. The specific

conductivities of all three ponds were similar during the spring

and summer of 1976. This is the period after hyacinth disappearance

on Ponds Two and Three, and during which time herbicide application

was occurring on Pond One. The specific conductivities of all

three ponds were similar during the summer of 1977. However,

during the fall and winter months of 1976-1977 and 1977-78,

the specific conductivity values varied greatly. After hyacinth

disappearance, Pond One always had the highest specific conduc-

tivity, and Pond Three had the lowest, while Pond Two was usually

intermediate. This is as expected, since water flowed from Pond

One, to Pond Two, to Pond Three; and nutrients were removed

by the growing vegetation in each pond. Therefore, the nutrient

levels (and therefore, specific conductivity) decreased in each

successive pond.



Nitrate-Nitrogen


Nitrate-nitrogen concentrations were determined only for

the first two years of the study. Since these procedures proved

to yield variable, and apparently unreliable data, these deter-

minations were discontinued in 1977.












1
425 +


400 +




Mi
s 350 / / ' 2-- .





275 +






250+ +
I :


225 +
'A M J J A S O N D J F M A M J J A S O N O J F M A M J J A S O N D F
1975 1976 1977

DATE

Figure 15. Citrus Ponds surface specific conductivity in micromhos/cm2
(-- = Pond One, ---= Pond Two, ....... = Pond Three).









Overall, the nitrate-nitrogen concentrations in all three

ponds usually fluctuated between 0.0 and 0.8 ppm. One large

peak of nitrate-nitrogen was found in each pond during the study

(Fig. 16).



Potassium


The concentration of potassium ranged from 2.3 to 19.4

ppm in Pond One, 0.8 to 21.6 ppm in Pond Two, and from 2.7 to

22.2 ppm in Pond Three (Fig. 17). Initially, potassium levels

were very low in Ponds Two and Three (treatment ponds) before

herbicide application. The potassium levels in these ponds

increased greatly after herbicide application while hyacinths

were dying and decaying, apparently as a result of potassium

released from decomposing hyacinths. A similar pattern was

observed in Pond One during its treatment in 1976. After open

water conditions existed, the potassium levels of all three

ponds seemed to stabilize between 7 and 14 ppm.



Total Phosphate-Phosphorus


The concentration of total phosphate-phosphorus ranged

from 0.0885 to 0.8200 ppm in Pond One, 0.1425 to 0.8330 ppm

in Pond Two, and from 0.1165 to 1.3095 ppm in Pond Three (Fig.

18). In the treatment ponds (Ponds Two and Three), total

phosphate-phosphorus increased greatly after chemically treating

the hyacinths, apparently due to release of phosphate-phosphorus

by decomposing vegetation. Total phosphate-phosphorus eventually












6.4 +


5.6


4.8 +
I

4.0 +


3.2 +


2.4 //


1.6 + i /


0.8 1
AI ..
S-4 /."
0.0 0 _ _ ___1


A 975 J A
1975


O N D J F M A


M J J
1976


A S O N D J F M A


M J 977
1977


A S 0 N D J F


DATE


Figure 16. Citrus Ponds surface nitrate-nitrogen concentrations in ppm
(--- = Pond One, ---= Pond Two, .......-= Pond Three).



















































Citrus Ponds surface potassium concentrations in ppm
(-- = Pond One, --- Pond Two, .......*= Pond Three).


I
24 +


21


10 +


15 +


12 +


9 +


6 +



3 t


o0


DA TE


Figure 17.




















































Citrus Ponds surface total phosphate-phosphorus concentrations
in ppm (-- = Pond One, ---= Pond Two, *.......= Pond Three).


1.28


1.12


0.96


0.80


0.64



0.48


0.32



0.16


0.00


DATE


Figure 18.






56

decreased to the lower levels found under open water conditions

(0.15 to 0.50 ppm) in 1977 due to removal of phosphate-phosphorus

by phytoplankton, and the flushing-out of excess nutrients by

incoming spring and runoff water. A similar large increase

occurred after chemical treatment in Pond One in 1976. As this

nutrient-enriched water moved downstream it would also elevate

the nutrient levels of Ponds Two and Three. Lower levels of

total phosphate-phosphorous were found in Pond One after open

water conditions were established.



Available Phosphate-Phosphorus


The concentration of available phosphate-phosphorus ranged

from 0.0115 to 0.6920 ppm in Pond One, 0.0055 to 0.9120 ppm

in Pond Two, and from 0.0010 to 1.3085 ppm in Pond Three (Fig.

19). During the study period, the concentrations of available

phosphate-phosphorus followed the same tendencies as total

phosphate-phosphorus.



Calcium


The concentration of calcium ranged from 17.25 to 49.00

ppm in Pond One, 16.50 to 48.40 ppm in Pond Two, and from 16.75

to 45.00 ppm in Pond Three (Fig. 20). Except for a low con-

centration of calcium in the three ponds during the winter

of 1975-1976, all the ponds normally showed calcium concentrations














1.6 +

1.4 +



1.2 +


1.0 +






0.6 +


0.64


0.2 4


0.0 +


1975 1976 1977

DATE


Figure 19. Citrus Ponds surface available phosphate-phosphorus concentrations
in ppm (- = Pond One, Pond Two, .......*= Pond Three).












I
55 +


50 +


45 +
I

40 +


35 +


30 +


25 +


20 +


15 +


1975 1976 1977

DATE


Citrus Ponds surface calcium concentrations in ppm
(-- = Pond One, ---= Pond Two, ........= Pond Three).


Figure 20.









ranging from 28 to 49 ppm. The concentration of calcium in all

three ponds seemed to be quite stable, and showed only a slight

increase during open water conditions.



Magnesium


The concentration of magnesium ranged from 3.2 to 17.3

ppm in Pond One, 4.9 to 17.2 ppm in Pond Two, and from 2.3

to 16.5 ppm in Pond Three (Fig. 21). The concentration of

magnesium was similar to that of calcium, but concentrations

of magnesium appeared to be fairly constant throughout the study

(with the exception of winter 1975-1976).



Dissolved Oxygen


The concentration of dissolved oxygen in the pond surfaces

during periods of dense hyacinth cover varied with the seasons

(due to changing air and water temperatures). Dissolved oxygen

concentrations under actively growing hyacinth mats were less

than 3.0 ppm in spring, less than 1.5 ppm in summer, and less

than 9.0 ppm during winter and fall (Fig. 22). Changing water

temperatures considerably influenced this, since the solubility

of oxygen in water increases with decreasing water temperature.

Air temperature, and its effect on the hyacinth mat, also in-

fluences the amount of dissolved oxygen. During fall and winter,

air temperatures are lower, thus slowing down plant growth.

Winter frosts also cause natural killing of the hyacinths, thus

reducing the size of the hyacinth mat. Lower air temperatures









































DA TE


Citrus Ponds surface magnesium concentrations in ppm
(--- = Pond One, ---= Pond Two, ........= Pond Three).


Figure 21.









































DATE


Citrus Ponds surface dissolved oxygen concentrations in ppm
(---- = Pond One, Pond Two, *.......= Pond Three).


Figure 22.









were generally associated with large open spaces developing in

the mat, allowing more oxygen to enter the water column. Further-

more, less oxygen is removed from the water for plant respiration

by the hyacinth roots since less biomass is found during the winter.

Surface dissolved oxygen concentrations dropped to less

than 1.0 ppm during chemical treatment of hyacinths. Within

six months after the initial herbicide applications in each

pond, the surface dissolved oxygen concentrations had increased

considerably. Surface dissolved oxygen concentrations were

much higher (normally four to sixteen ppm) and fluctuated

greatly (due to changes in water temperature, solar radiation,

phytoplankton populations, etc.) after open water conditions

existed.

The concentration of dissolved oxygen at one meter depths

below the pond surfaces is shown in Fig. 23. The highest

oxygen concentrations in all ponds were found during the cool

water periods (fall and winter). Little oxygen was found at

one meter depths during warm water periods (usually less than

0.5 ppm) under actively growing mats. Dissolved oxygen levels

at a one meter depth improved yearly after hyacinths disappeared

and open water conditions existed.

In summary, dissolved oxygen concentrations were minimal

under actively growing dense hyacinth mats and chemically

treated dying hyacinth mats, and were maximal during cool water

periods when the vegetation cover was reduced. Figures 24-28 show

oxygen-temperature profiles for specific sampling dates during

the study.












































M A M J J A SON D
1977


DATE


Figure 23. Citrus Ponds one meter depth dissolved oxygen concentrations
in ppm (-- = Pond One, ---= Pond Two, ........= Pond Three)


1
16 +


'4 +


12 +


10 +


1975










WATER TEMPERATURE (oC)
16.0 14.0 12.0 18


16 14


DISSOLVED OXYGEN (PPM)


Pond Two
profiles
hyacinth


dissolved oxygen and temperature
beneath actively growing water
populations before chemical treatment.


a) April 8, 1975


b) April 22, 1975


(--- =water temperature in degrees centigrate,
........- dissolved oxygen concentration in ppm).


SURF


Figure 24.










Figure 25. Pond Two dissolved oxygen and temperature profiles beneath chemically treated water
hyacinth populations.



a) June 4, 1975, three weeks after chemical treatment (a thick cover of dead
and decaying water hyacinths remained on the pond surface).












b) October 20, 1975, five months after chemical treatment (large floating mats
of decaying organic material, or "sudds", were found on the pond surface).



(- = water temperature in degrees centigrade,
----- = dissolved oxygen concentration in ppm.)










WATER TEMPERATURE (OC)
26 24 22 20 18 16 24 22 20
SURF- L 1' I I I RF- I






D
E
p 1M M
T
H

I
N
FOND TWO POND TWO
M 6-4-75 10-20-75
E
T 2M 2M-
E
R
S


DISSOLVED OXYGEN (IPM)











Figure 26. Pond Two dissolved oxygen and temperature profiles after removal of water hyacinth
populations by chemical treatment, and establishment of open water conditions.


a) December 10, 1975, seven months after chemical treatment, and one month after
open water conditions were established.









b) January 9, 1975, two months after open water conditions were established.









c) April 15, 1975, five months after open water conditions were established.


(--- = water temperature in degrees centigrade,
------ = dissolved oxygen concentration in ppm.)











18 16 14


WATER TEMPERATURE (OC)
12 10


22 20 18


POND TWO
12-10-75


0 2 '
10 6 2


POND TWO
1-9-76


POND TWO
4 -15-76











Figure 27. Pond Two dissolved oxygen and temperature profiles after establishment of open
water conditions.


a) July 27, 1976, eight months after open water conditions were established
(fourteen months after chemical treatment).









b) September 28, 1976, ten months after establishment of open water conditions.









c) January 22, 1977, fourteen months after open water conditions were established.


(--- = water temperature in degrees centigrade,
------- = dissolved oxygen concentration in ppm.)











28 26 211


SURF


WAT'l'ER TEMP'ERATIRE ( Oc )
28 P 211


12 10 8


DI SSI VE'D OXYGENU (111M)









Figure 28. Pond Two dissolved oxygen and temperature profiles after establishment of open water
conditions.


a) May 3, 1977, eighteen months after open water
(two years after chemical treatment).


conditions were established


b) August 4, 1977, twenty-one months after open water conditions were established.









c) November 16, 1977, two years after open water conditions were established (two
and a half years after chemical treatment).


( -- = water temperature in degrees centigrade,
-------- = dissolved oxygen concentration in ppm.)










WATER TEMPERATURE (OC)
26 24 22 30 28 26
SIIRF I I 1_ I URF I I I







D
E Mi




T


I
N

M
E 2M- 2NM
T POND TWO POND TWO
E 5-3-77 8-4-77
R


DISSOLVED OXYGEN (PPM)









Dissolved oxygen was found to be negatively correlated with

percent total vegetation cover, and positively correlated with

light penetration in the pond surfaces and depths. Therefore,

the greater the amount of vegetative cover, the less the light

penetration, and the less dissolved oxygen was found. Dissolved

oxygen was also negatively correlated with water temperature

in the pond depths.



Water Temperature


Water temperatures fluctuated between 8.5 and 32.6C during

the study period. Surface water temperatures (Fig. 29) showed

a slightly greater range than did one meter depth water temper-

atures (Fig. 30). The yearly range of water temperatures

increased after water hyacinths were removed (1976), and open

water conditions became established (1976-1977). The smallest

yearly range of water temperature occurred when the ponds had

a thick cover of water hyacinths (1975). The hyacinth mats

apparently acted as an insulative barrier which kept the pond

water temperatures cooler than air temperatures in summer and

warmer than air temperatures during winter.

The average difference between surface and one meter depth

water temperatures was 2.6C before and during treatment of

hyacinths, and 1.3C after hyacinth disappearance in Pond One

(control pond). The average difference was 4.2C before and

during hyacinth treatment in Pond Two (treatment pond), and

1.7C after hyacinth disappearance. The average difference was












I
33 *


30 +


27 +


24 +


21 +


18 +


15 +


12 +


9 +


A






.7:


A M J A A S O N D J F M A M A A


1976


M J J A S O N D
1977


J F


DAATE


Citrus Ponds surface water temperature in degrees centigrade
(--- = Pond One, --- Pond Two, .......= Pond Three).


$;










I:



I:\

/


I.





I ~


II





tV


1975


Figure 29.


I


I


^ "'


S II u J r M A







































1975 1976 1977

DA TE


Citrus Ponds one meter depth water temperature in degrees
centigrade (- = Pond One, ---= Pond Two, *.......= Pond Three).


Figure 30.









4.7C before and during treatment in Pond Three, and 1.7C after

hyacinth disappearance. There was a larger temperature difference

between pond surfaces and one meter depths when the ponds were

covered by dense hyacinth mats. Less difference in water temp-

erature occurred with depth after mat disappearance.



Secchi Disk


Light penetration was determined by the depth of Secchi

disk disappearance (Fig. 31). Secchi disk readings were minimal

during periods of dense hyacinth cover and during periods of

heavy phytoplankton growth (summers) after hyacinth disappearance.

Secchi disk readings were maximal during cool water periods

(late fall and winter) before and after hyacinth disappearance

when phytoplankton populations were minimal.

Secchi disk disappearance in the pond surfaces was negatively

correlated to total phytoplankton, total blue-green algae, and

water temperature.



Light Penetration


Light penetration was also measured by means of a light

meter using a quantum type probe. Surface light penetration

was measured at a depth of one centimeter below the pond surfaces

(measuring the amount of light entering the water column).

Surface light penetration readings were fairly variable, depending

on the amount of vegetation present, which caused shading effects

on the ponds beneath (Fig. 32). In general, surface readings













2.4 +


2.1 +


1.8 +

1.5




1.2 +


0.9 +-


0.6 +


0.3 +


o.O +
A M J J A S
1975


DATE


Citrus Ponds depth of light penetration, measured as the depth
(in meters) of Secchi disk disappearance
(- = Pond One, ---= Pond Two, .......*= Pond Three).


Figure 31.












1600 +


1.00 t. i


1200 + 2 I '


R 1000 +
0 I II

I \
N 800 + I /


S I I: \ :

400 \ I
E \



200 +



A M J J A S O N D J F M A M J A S O N D J F M A M J J A S O N D F
1975 1976 1977

DArE

Figure 32. Citrus Ponds surface light penetration, measured as micro-
einsteins/M2/sec by light meter
(- = Pond One, ---= Pond Two, ....... = Pond Three).









showed an increasing trend, and were less variable after hyacinth

disappearance. The graph depicting light penetration at one

meter depths (Fig. 33) shows a much closer relationship between

vegetation cover and light penetration than did surface light

penetration. Light penetration was minimal at the one meter level

when hyacinth mats were present, and when phytoplankton blooms

were occurring. Light penetration was maximal during winter

(cool water months), when vegetation cover and phytoplankton

blooms were minimal. Figures 34-35 show light penetration

profiles for several sampling dates during the study.

Light penetration in the surface of Pond One was negatively

correlated with total chrysophytes, total phytoplankton diatoms,

and percent total vegetation cover, and positively correlated

with dissolved oxygen. No significant correlations were found

in the surface of Ponds Two and Three.

Light penetration was negatively correlated with both water

temperature and percent total vegetation cover, and positively

correlated to dissolved oxygen in the pond depths.



Percent Total Vegetation Cover


Estimates were made throughout the study to determine what

percentage of the pond surfaces were covered with floating vegetation

(Fig. 36). The water hyacinth and pennywort populations decrease

their percentage of surface coverage during winter in northern

Florida due to frost damage and decreased growth rates.












I
320 +


280 1


240
M I '"

R 200 +


N160


S 120 + /





So + ..I f .{ /




A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F
1975 1976 1977

DATE

Figure 33. Citrus Ponds one meter depth light penetration, measured as
microeinsteins/M2/sec by light meter
(- = Pond One, --- = Pond Two, *....... = Pond Three).











Figure 34. Pond One light penetration profiles, measured as
microeinsteins/M2/sec with depth. Light penetration
measurements were taken above and below the pond
surface.


a) June 4, 1975, profile beneath actively growing
hyacinth populations (thick mat of hyacinths
was found above the pond surface).











b) December 10, 1975, profile beneath actively
growing water hyacinth populations (thin mat
with large holes, due to frost kill-back).











c) August 26, 1976, profile beneath large floating
mats of dead and decaying organic material
("sudds") four months after chemical treatment
of water hyacinth populations.













MICROEINSTEINS
2000 1600 1200 800 400 0
MAT i ,
TOP


WATER'
SURF

POND ONE 6-4-75
50

100


D 150
E YAT 2000 1600 1200 800 400 0
P TOP
T I'ATER
H SURF

I 50
N POND ONE 12-10-75

C 100


150

AIR 2000 1600 1200 800 400 0
'IATER
SURF

50 -
POND ONE 8-26-76
100 -















Figure 35. Pond One light penetration profiles after establishment
of open water conditions measured as microeinsteins/M2/
sec with depth.


a) February 22, 1977, profile
disappearance of sudds and
open water conditions (ten
chemical treatment).


four months after
establishment of
months after


b) June 3, 1977, profile eight months after
established open water conditions.










c) January 18, 1978, profile fifteen months after
established open water conditions (twenty-
one months after chemical treatment).
























U)>










C) c
0



0
on c n ~



U) o pi~











C)
H









P1


O
0



0\













128 +


112 +


96 t


80 4-
I

64 +


48 -


32 +


16 +


0 +


A S O ND J F MA M J J A S
1975 1976

D)ATEf


1977


Citrus Ponds percent of total vegetation cover (water hyacinth,
pennywort, and duckweed populations included) on the pond
surfaces ( = Pond One, ---= Pond Two, *.......= Pond Three).


II\







**. I


Figure 36.









Duckweed only appeared in quantity in Pond Two during 1976

when it covered up to 89 percent of the pond surface. In general,

most floating vegetation problems were well under control by 1977

except for occasional small recurring marginal fringes. The

percentage of total vegetation cover in 1977 for Ponds One and

Two varied between 1 and 15 percent, and 1 to 30 percent in Pond

Three.



PhytopIankton


The phytoplankters to be discussed in the following sections

are grouped according to their placement in the classification

hierarchy. Total phytoplankton is discussed first, followed by

discussions of the major algal groups (blue-green algae, chry-

sophytes, and green algae) and their dominant species found

during the study.



Total Phytoplankton


Total surface phytoplankton ranged from 6.84 X 103 to 1.07

X 107 cells/liter in Pond One, 5.81 X 103 to 5.31 X 107 cells/

liter in Pond Two, and from 3.48 X 102 to 7.95 X 10 cells/

liter in Pond Three during the study (Fig. 37).

Total phytoplankton was found to be maximal during cool

water periods and minimal during warm water periods under actively

growing hyacinth mats. This seems to be due to increased light

penetration during winter when the hyacinth coverage decreased,











I
8.0 +
L

0 *1 \
: /i \ 1 /- 1
G 7.2 + ,/





L 5.6 + I
A i \I I
N
K I
0 co
o: !' ." ,,- : *-. .
C 4.0 +
E
L "
S 3.2+
L
I
1 2.4 +


1.6 +
A M J J A S O N D J F M A M J A SO N D J M A J A S N J F
1975 1976 1977

DATE
Figure 37. Citrus Ponds total surface phytoplankton, expressed as the
number of cells/liter in log1o
(---- = Pond One, Pond Two, ........= Pond Three).









and decreased light penetration in summer when hyacinth mats

are growing most actively.

Total phytoplankton decreased due to decreased light penetration

and foul water conditions after the hyacinths were treated, and

later increased after open water conditions were established.

Total phytoplankton was minimal during cool water periods and

maximal during warm water periods after open water conditions were

established.

Total phytoplankton was positively correlated with water

temperature and pH, and negatively correlated with Secchi disk

disappearance in the surfaces of Pond Two and Three. Total

phytoplankton was negatively correlated with magnesium in the

surface of Pond One.

Stepwise multiple regressions were used to select the best

possible models to explain the variations in the data. Stepwise

multiple regressions selected soluble salts as the best model

for Pond One, pH, bicarbonate, soluble salts, and specific con-

ductivity for Pond Two, and bicarbonate and percent total vegetation

cover for Pond Three.



Total Blue-Green Algae


Total surface blue-green algae reached a maximum of 1.06 X

107 cells/liter in Pond One, 5.31 X 107 cells/liter in Pond Two,

and 2.61 X 10 cells/liter in Pond Three during the study (Fig.

38).











8 *






6i+


Sj












I
+~


1975 1976 1977
DA TE


Citrus Ponds total surface blue-green algae, expressed as the
number of cells/liter in logo
( = Pond One, --- Pond Two, .......* = Pond Three).


Figure 38.









Total blue-green algae showed a distribution similar to that

of total phytoplankton in all three ponds. This was not unexpected

since on many sampling dates total phytoplankton was mostly

composed of blue-green algae.

Blue-green algae were prevalent throughout the year beneath

actively growing hyacinth populations, but decreased rapidly

when hyacinth populations were dying (after herbicide application).

Blue-green algae populations were minimal during cool water

periods, and maximal during warm water periods after hyacinth

disappearance (open water conditions).

Total blue-green algae were positively correlated with water

temperature, and percent total vegetative cover, and negatively

correlated with Secchi disk disappearance in the pond surfaces.

Stepwise multiple regressions were used to select the best

possible models to explain the variations in the data in all ponds.

Stepwise multiple regressions selected water temperature as the

best model for Pond One, nitrate-nitrogen and Secchi disk dis-

appearance for Pond Two, and bicarbonate and specific conductivity

for Pond Three.



Anabaena Schmerer Elenkin


This filamentous blue-green alga reached a maximum of 1.03

X 105 cells/liter in Pond One, 5.00 X 10 cells/liter in Pond

Two, and 6.55 X 105 cells/liter in Pond Three during the study

(Fig. 39).











1
8 +
I
7 +


6 -


5+


4 +


3 +


2 +


1 +


0 + =


A M J J A S O N D J F M A M JJ
1975 1976


A S 0 N D


Ei :1
I: 3


J F M A M J J A S O N D J F
1977


DATE


Figure 39.


Citrus Ponds surface Anabaena Schmerer, expressed as the
number of cells/liter in logi0
(----= Pond One, ---= Pond Two, ........= Pond Three).


I I I
I I


I\



I' I~
i/ i\



II I
\I
|


V- --









A. Schmerer populations were maximal on one sampling date

in the spring of 1976 in all three ponds. Other blooms occurred

in Ponds One and Two during summer and fall 1977.

A. Schmerer appears to reach maximal populations during

warm water periods under open water conditions.

No significant correlations were found in any of the three

ponds, and stepwise multiple regressions did not provide significant

models.



Anbaena spiroides Klebahn


Anabaena spiroides was not found during the study in Pond

One. A. spiroides bloomed during the summers of 1976 and 1977

in Ponds Two and Three. It reached a maximum of 4.06 X 10

cells/liter in Pond Two, and 1.59 X 106 cells/liter in Pond Three

during the study (Fig. 40).

A. spiroides, like A. Schmerer, appears to reach maximal

populations during warm water periods under open water conditions.

No significant correlations were found in any of the three

ponds, and stepwise multiple regressions did not provide significant

models.



Oscillatoria linmetica Lemmermann


This filamentous blue-green alga reached a maximum of 1.85

X 10 cells/liter in Pond One, 1.78 X 10 cells/liter in Pond Two,

and 1.89 X 10 cells/liter in Pond Three during the study (Fig. 41).
























1




:
:











i


i


V.




kt~I

Fl

F


S if


F


A M J J A S
1975




Figure 40.


0 N 0 J F M


Citrus
number
(--


A M J J
1976


A S O N D J F M A M J J A S O
1977

DATE


N 0 J F


Ponds surface Anabaena spiroides, expressed as the
of cells/liter in log10
= Pond One, ---= Pond Two, ........ = Pond Three).


___ m_~ I____


1 111_


I P P A P B

















































Citrus Ponds surface Oscillatoria limnetica, expressed as the
number of cells/liter in logo1
(-- = Pond One, ---= Pond Two, .......= Pond Three).


I
6.4 +


5.6 +






4.0 +
,.o +


3.2 +


2.4 +


1.6 +


0.8 +


0.0 +


UATE


Figure 41.




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