Characterization of Satellite DNA Dinoflagellates Glenodinium Two
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COMPARATIVE POPULATION DYNAMICS OF FRESHWATER DINOFLAGELLATES OF THE GENERA PERIDINIUM AND PERIDINIOPSIS
by
Andy Kyle Canion
A thesis submitted to the faculty of The University of Mississippi in partial fulfillment of the requirements of the Sally McDonnell Barksdale Honors College.
Oxford
May 2004
Approved by
___________________________________ Advisor: Dr. Clifford Ochs
___________________________________ Reader: Dr. Tamar Goulet
___________________________________
Reader: Dr. Michael Mossing
© 2004 Andy Kyle Canion
ALL RIGHTS RESERVED
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ACKNOWLEDGEMENTS
I would like to express my gratitude to everyone who provided assistance with this research. Dr. Susan Carty of Heidelberg College and Dr. Jack Holt of Susquehanna University provided much needed help with the identification of dinoflagellate species. Fortune Ogbebo and Jim Weston at the University of Mississippi and John Hart at the Center for Water and Wetland Resources assisted with sample processing. The Sally McDonnell Barksdale Honors College provided the financial support for this research. Lastly, I would like to thank Dr. Cliff Ochs, who served as the advisor for this project. The involvement of all these people was essential for the advent and completion of this project.
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ABSTRACT ANDY KYLE CANION: Comparative Population Dynamics of Freshwater
Dinoflagellates of the genera Peridinium and Peridiniopsis (Under the direction of Cliff Ochs)
Freshwater dinoflagellates, like their marine relatives, have the potential to
reach large population sizes known as blooms. Though they are not toxic like some
marine forms, freshwater blooms may have a large impact in their respective
ecosystem. This study investigated the temporal and spatial changes in population
density of four Peridinium species (P. deflandrei, P. volzii, P. wisconsinense, and P.
limbatum) and one Peridiniopsis species (Peridiniopsis polonicium) in Boondoggle
Lake, a shallow lake (4.5 m) in northern Mississippi (Lafayette Co.). On each
sampling date, measurements of the abiotic environment were made, including
dissolved oxygen, temperature, pH, and turbidity. Also, water samples were taken
from three depths: 0.25 m, 1 m, and 2 m. Estimates of total dinoflagellate density
were made by enumeration of concentrated samples on LM slides. Individual species
were identified using SEM, and estimates of the relative abundance of each species
were made at the SEM, which allowed estimates of the actual densities of each
species to be made. One species, P. deflandrei, was by far the most dominant in the
summer bloom (90% of the total dinoflagellate population) and reached a maximum
population density of 2.75 X 105 cells/ L. P. volzii was the most abundant species in
the spring and late fall, with its maximum density being 5.7 X 104 cells/ L. The other
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three species had temporal patterns similar to either P. deflandrei or P. volzii but
never comprised more than 25% of the total dinoflagellate population. P. limbatum
reached maximum densities in the spring and fall, similar to P. volzii. P.
wisconsinense and Peridiniopsis polonicium reached maximum densities in the
summer, similar to P. deflandrei. The species composition and population density of
dinoflagellates in Boondoggle Lake are determined by many environmental factors.
Those that are likely to be most important include low nutrient levels, an acidic pH
(5.5-6.5), warm temperatures, summer anoxia, wind protection, and interspecific
competition.
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TABLE OF CONTENTS
LIST OF FIGURES………………………………………………………………….vii SECTION 1: INTRODUCTION……………………………………………………...1 SECTION 2: MATERIALS AND METHODS……………………………………...11 SECTION 3: PHYSICAL AND CHEMICAL CHARACTERISTICS OF BOONDOGGLE LAKE………………………………………………17 SECTION 4: INDENTIFICATION OF DINOFLAGELLATE SPECIES FROM BOONDOGGLE LAKE………………………………………………28 SECTION 5: SPATIAL AND TEMPORAL PATTERNS IN POPULATION FOR DINOOFLAGELLATES IN BOONDOGGLE LAKE……………….41 SECTION 6: DISCUSSION…………………………………………………………55 LIST OF REFERENCES…….………………………………………………………61
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LIST OF FIGURES
Figure 1.1: Key morphological features of freshwater armored dinoflagellates...........3 Figure 1.2: Basic life cycle of sexually reproducing freshwater armored dinoflagellates…………………………………………………………….7
Figure 3.1: Temperature and dissolved oxygen profiles for selected dates beginning March 2002 and ending July 2003………………………………..…18-20
Figure 3.2: Temporal patterns of pH for three depths: 0.25 m, 1 m, and 2 m……….23 Figure 3.3: Temporal patterns in Secchi depth………………………………………24 Figure 5.1: Total dinoflagellate population density………………………………….42
Figure 5.2: Population proportion at 0.25 m…………………………………………44 Figure 5.3: Population proportion at 1 m…………………………………………….45 Figure 5.4: Population proportion at 2 m…………………………………………….46 Figure 5.5: Individual population trends at 0.25 m…………………………………..48 Figure 5.6: Individual population trends at 1 m……………………………………...49 Figure 5.7: Individual population trends at 2 m……………………………………...50 Figure 5.8: Correlation of total dinoflagellate density to temperature……………….53 Figure 5.9: Correlation of P. deflandrei density to temperature……………………..54
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Section 1: General Introduction
1.1 Overview of Dinoflagellates
Dinoflagellates are a monophyletic group of single-celled eukaryotes that could
originally be found in the classification schemes of both zoologists and botanists.
Although they share cellular features with members of both the plant and animal
kingdom, they are now believed to be most closely related to either photosynthetic
protists or protozoa (Carty 2003). Molecular evidence suggests they branched from the
eukaryotic lineage early in the evolution of eukaryotes (Herzog 1986). At present,
approximately 2000 extant species of dinoflagellates have been identified (Pfiester and
Anderson 1987).
The most extensive studies of dinoflagellates have been in marine environments
due to their important ecological roles and potential detrimental effects on marine biota
as well as humans. Blooms of marine dinoflagellates known as red tides have the
potential to cause fish kills, and dinoflagellate toxins, which are produced only by marine
forms, can cause human illnesses such as toxic shellfish poisoning and ciguatera (Graham
and Wilcox 2000).
Freshwater dinoflagellates, although not as dangerous to humans, can have an
equally large role in their respective ecosystems. Freshwater blooms of the genera
Ceratium and Peridinium have been documented in numerous lakes (Moore 1981;
Pollingher and Hickel 1991; Stewart and Blinn 1976; Whiting et. al. 1978; Wu and Chou
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1998; Yan and Stokes, 1978). Certain Peridinium blooms have been known to reach high
enough population densities to be labeled as freshwater “red tides.” One such red tide
was documented in Clear Lake, California, where Peridinium pernardii reached densities
of 5 X 106 cells/ L (Horne, et. al. 1971). Another freshwater bloom of Peridinium with
densities reaching 10-93 X 106 cells/L occurred in an oligotrophic reservoir near Tokyo
in 1975 (Nakomoto 1975). A bloom of Peridiniopsis polonicium was responsible for fish
kills in Lake Sagami near Tokyo, one of the few cases of a toxic freshwater dinoflagellate
bloom (Hashimoto, et. al. 1968).
Below, I review the basic biology of dinoflagellates, including morphology,
classification, nutrition, life history, and ecology. This review focuses on motile
freshwater armored dinoflagellates and the two genera that were investigated in this
study, Peridinium and Peridiniopsis.
1.2 Morphology and Classification
Freshwater dinoflagellate species show diverse patterns of morphology. They are
loosely grouped in the categories of thecate (armored) and athecate (naked), depending
on the presence or absence of sub-membranous cellulose plates. If present, the collection
of plates is known as the theca (Taylor 1987). The two genera of focus in this study,
Peridinium and Peridiniopsis, are thecate genera. A diagram of a freshwater armored
dinoflagellate is shown in Figure 1.1. The view is of the ventral side. Important features
to note are the cingulum (girdle), sulcus, flagella, epitheca, hypotheca, and sutures. One
flagellum lies in the transverse groove known as the cingulum (also girdle). The other is
found in the longitudinal groove, the sulcus.
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Figure 1.1: Key morphological features of freshwater armored dinoflagellates (Modified after Lefevré 1932)
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The epitheca and hypotheca refer to the collection of thecal plates above and below the
cingulum respectively. The ridges where thecal plates meet are known as sutures (Taylor
1987). Classification of freshwater armored dinoflagellates is based on the arrangement
and number of the thecal plates (Carty 1986).
1.3 Nutrition
Dinoflagellates are also diverse in their modes of nutrition. Autotrophic,
auxotrophic, mixotrophic, and heterotrophic forms have been documented (Carty 2003,
Holt and Pfiester 1981). Only six freshwater species have been documented as
completely autotrophic, meaning they require no organic substances for growth in the
light. Four of these are species from the genus Peridinium: P. cinctum f. ovoplanum, P.
inconspicuum, P. volzii, and P. willei (Gaines and Elbrächter 1987). Many
photosynthetic dinoflagellates require vitamins for growth (auxotrophy). There are only
three vitamins that are known to be required by auxotrophic algae: B12, thiamine, and
biotin (Graham and Wilcox 2000), and dinoflagellates have been shown to require one,
two, or all three of these vitamins for growth (Gaines and Elbrächter 1987). Pure
heterotrophs (living exclusively on organic compounds) comprise approximately half of
all dinoflagellates. In freshwater systems, photosynthetic species dominate, but
heterotrophic benthic species are not uncommon (Gaines and Elbrächter 1987).
1.4 Life History
An important characteristic of the motile freshwater dinoflagellate life cycle is
the alternation between a swimming, vegetative form and a resting stage known as a cyst
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(Pollingher 1988). Cyst formation is associated with most sexually reproducing forms
and occurs after a zygote ceases to be motile and forms a thick cell wall. Encystment is
believed to be an adaptation for surviving environmental stress, and it usually occurs in
conjunction with specific environmental conditions (Pollingher 1988). Some of the
possible environmental factors that can lead to encystment include temperature, nutrient
depletion, light intensity, and changes in concentration of dissolved gasses. Of these,
nutrient depletion of nitrogen has been best demonstrated to induce encystment in
cultures (Pfiester and Anderson 1987). Sexual reproduction followed by encystment was
shown to be induced by nitrogen depletion in cultures of four Peridinium species:
Peridinium cinctum, Peridinium willei, Peridinium gatunense, and Peridinium volzii.
(Pfiester 1975; Pfiester 1976; Pfiester 1977; Pfiester and Skvarla 1979).
Dinoflagellates undergo asexual reproduction and sometimes sexual reproduction
depending on the species and environmental conditions. The vegetative (also called
assimilative) stage of freshwater armored dinoflagellates is haploid and divides asexually
through mitosis (Pfiester and Anderson 1987). Cells increase their size before dividing,
which is accomplished by expanding the theca at the sutures between thecal plates.
These expanded areas are referred to as intercalary bands (Taylor 1987).
Sexual reproduction begins when the haploid vegetative stage forms gametes
through mitosis. Gametes then fuse to form a planozygote. The planozygote is motile,
with two longitudinal flagella, and can remain motile to continue cell growth (Pfiester
and Anderson 1987). Planozygotes accomplish cell enlargement in the same manner as
vegetative cells by expansion at the sutures between thecal plates (Pfiester and Skvarla
1980). Formation of a hypnozygote occurs when the planozygote loses motility and
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forms a thick cell wall. Hypnozygotes rest on the lake bottom until conditions are right
for excystment, at which time vegetative cells are returned to the water column. Meiosis
must occur between formation of the planozygote and excystment of the hypnozygote,
and when it occurs varies among taxa.
The causes and mechanisms of sexual reproduction have been studied in only 22
of all 2000 dinoflagellate species (Pfiester and Anderson 1987). As previously
mentioned, many environmental factors are thought to induce sexual reproduction and
subsequent encystment. In previous studies of freshwater dinoflagellates, environmental
cues have been shown to influence the emergence of vegetative cells from resting stages
(Pfiester and Anderson 1987; Kawabata and Ohto 1989; Anderson et al. 1987).
Life history traits are an important deterministic component of the population
dynamics and ecology of dinoflagellates because reproductive strategies influence
temporal and spatial patterns in dinoflagellate abundance. Figure 1.2 shows the basic
sexual and asexual life cycle of freshwater armored dinoflagellates.
1.5 Ecology
Dinoflagellates usually reach their maximum population size in the summer
months. Though they are usually found in low numbers, some species may form large
blooms given the correct environmental conditions. Members of the genera Ceratium
and Peridinium are well studied bloom formers (Carty 2003; Pollingher 1988). The
population ecology of freshwater dinoflagellates is widely thought to be influenced by
many bottom-up and top-down control factors. Bottom-up factors include pH,
temperature, organic matter, inorganic ions (Ca, Cl, N, P), light intensity, vitamins, and
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Figure 1.2: Basic life cycle of sexually reproducing freshwater armored dinoflagellates (Modified after Carty 2003)
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inoculum from cysts. Top- down factors include predation, disease, life history traits
(cyst formation), lake outflow, and turbulence (Carty 2003; Pollingher 1988; Popovsky
and Pfiester 1990). The effects of bottom-up and top-down factors on patterns of
freshwater dinoflagellate abundance have been investigated in many studies. A brief
review of the well-studied control factors is now presented.
Lake pH has been demonstrated to influence the growth rate of freshwater
dinoflagellates. However, the effect of pH on growth rate is variable across species. In
the genus Peridinium, studies of laboratory cultures have shown species with maximum
growth occurring at a pH ranging from 5.5 (P. limbatum) to 8 (P. cinctum), and one
species, Peridinium inconspicuum, showed little change in growth rate over a range of
5.5-8.5 (Holt 1981; Pollingher 1988).
The influence of temperature on freshwater dinoflagellate populations is only a
general trend. Most dinoflagellates show maximum growth during the summer, but there
is a wide tolerance range for temperature. That is, dinoflagellates are not strong
stenotherms (Carty 2003; Pollingher 1988). Though most freshwater dinoflagellates
form cysts during the winter, some have been found in the water column throughout an
entire year. These include Peridinium bipes and Peridinium willei (Pollingher 1988).
Freshwater dinoflagellates are not tolerant of oxygen stress. Low oxygen levels
can cause Peridinium cinctum fa. Westii to shed its flagella, shed its theca, and become
immobile. Insufficient oxygen has also been shown to induce encystment in Peridinium
species from Lake Kinneret (Pollingher 1987). In situ observations of Peridinium in
Lake Kinneret and Ceratium in Esthwaite Water have revealed that these freshwater
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dinoflagellates are rarely, if ever, found in anoxic hypolimnic waters (Pollingher 1988;
Harris et. al. 1979).
The concentrations of inorganic nutrients, particularly nitrogen and phosphorus,
are important in determining the growth of dinoflagellates. Freshwater dinoflagellates
are generally more abundant relative to other algal taxa when nutrients are low. It is
thought that the resilience of dinoflagellates under low nutrient conditions along with
reduced competition from other algae is largely responsible for their summer success in
nutrient poor systems (Pollingher 1987; Pfiester 1971). Mechanisms for tolerance of low
nutrient levels have been studied. These include luxury consumption of phosphorus, long
generation times, and vertical migration to obtain nutrients (Heany and Eppley 1981;
Carty 2003; Pollingher 1988). As mentioned earlier, low nitrogen levels may contribute
to sexual reproduction and encystment of freshwater dinoflagellates (Pfiester and
Anderson 1987; Pfiester 1975, 1976, 1977; Pfiester and Skvarla 1979).
Usually, photosynthetic dinoflagellates prefer abundant light and are concentrated
in the upper layers of the water column (Pollingher 1987). Their motility makes them
able to move to an optimal depth for photosynthesis as well as nutrients. Dinoflagellates
have been shown to undergo vertical diel migrations, which are thought to be most
influenced by light, temperature, and nutrient availability. However, these migrations are
frequently variable for different species (Heany and Eppley 1981). One study of vertical
migration in Ceratium hirudinella suggests that a compromise between light availability
from the surface and nutrients concentrated at depth will determine the depth where
maximum densities of dinoflagellates will occur (Heany and Furnass 1980). Irradiation
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is important not only in how productive dinoflagellates will be but also where they will
be found in the water column.
The role of top-down factors in the population ecology of freshwater
dinoflagellates also has been investigated, but to a lesser extent. Measurements of
physiological death of Peridinium in Lake Kinneret showed a decrease of 8-10% during
exponential growth and 40-80% at the end of the summer bloom (Serruya et. al. 1975).
Large freshwater dinoflagellates, such as some species of Peridinium and Ceratium, are
subject to grazing only by certain species of rotifers and in some cases, fish. Parasitism
by chytrid fungi has been documented in Peridinium (Pollingher 1988).
Other factors contributing to loss include turbulence, which was associated with a 62.5%
death rate in continuously shaken Peridinium cultures (Pollingher and Zemel 1981), and
lake outflow, which was observed to remove 7.65 X 1013 dinoflagellate cells/ day from a
lake population (Heany and Talling 1980).
1.6 This Study
The objective of this study was to describe the population dynamics of the
freshwater armored dinoflagellates in Boondoggle Lake (Oxford, Mississippi). This
objective was accomplished by collecting physical and chemical data from the lake,
identifying the species of freshwater armored dinoflagellates present, and estimating
population densities of dinoflagellates throughout the study period.
There is a paucity of information on the ecology and distribution of freshwater
dinoflagellates. This study will provide some of the much needed information on the
dinoflagellates in Mississippi.
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Section 2: Materials and Methods 2.1 Sampling site and surrounding area
Boondoggle Lake is a man-made lake located approximately 10 miles east of
Oxford, MS on the edge of Holly Springs National Forest and is approximately 70 yrs
old. The lake has an elevation roughly 120 m above sea level and is surrounded by
mixed bottomland forest on all sides. It is about 1.5 hectares in surface area and has a
maximum depth of approximately 4.5 m. It undergoes one major period of
stratification in the summer and has been observed to go through a mixing and
restratification in the fall after intense rain. The lake experiences anoxia in the
summer that may begin as high as 1.5 m from the surface, and it exhibits a dark
reddish-brown color during summer months, which becomes clearer upon cooler
temperatures and mixing.
2.2 Water Sampling, Temperature and Oxygen Measurements
Water samples were collected on 44 dates between March 2002 and
September 2003. For each sampling date, water samples and measurements were
taken at a marked point near the middle of the lake (depth ~4 m). Sampling was
performed during mid-day (between 11:00 a.m. and 1:00 p.m.) each date and took
approximately 45 minutes to complete. Samples were returned to the lab and
processed within approximately one hour of sampling time.
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Two replicates of water samples were taken at 0.25 m, 1 m, and 2 m using 2-
liter Nalgene® plastic bottles. A peristaltic pump was used to obtain samples from
1 m and 2 m. Water was run through the pump at each depth before filling the bottles
in order to prevent contamination of samples by water from a different depth.
Along with collection of water samples, basic physical and chemical data
from the lake were collected on each sampling date. Secchi depth measurements
were used to estimate light penetration. A YSI model 57 oxygen meter was used to
measure dissolved oxygen and temperature profiles with readings taken every 0.25 m
from the surface to a depth of 4 m.
2.3 Water Sample Measurements and Preservation
In the lab, 200 mL of each water sample were vacuum filtered through a
47 mm Whatman® GF/F-filter. The filters were wrapped in aluminum foil and saved
in a -800 C-freezer until needed for HPLC pigment analysis. The filtrate was saved in
Whirl pak® bags in a -200 C-freezer for nutrient measurements.
Turbidity was measured for all unfiltered water samples using a Hach model
2100A Turbidimeter. The turbidimeter was calibrated using a 9.9 NTU Gelex®
secondary turbidity standard.
The pH of unfiltered water samples was determined using a Fisher Scientific
Accumet® 1001 pH meter. The pH meter was standardized using a pH 4 potassium
biphthalate buffer solution and a pH 7 potassium phosphate monobasic-sodium
hydroxide buffer solution.
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Water samples to be used for enumeration of dinoflagellates were
concentrated before being preserved. One liter of water from each of two replicates
from each depth was filtered through a 20 µm mesh filter and concentrated to a
volume of approximately 20 mL. These water samples were placed into plastic vials
and fixed with 200 µL of acid Lugol’s solution so that they could be used later for
enumeration and identification. Also, for most dates, 100 mL of unconcentrated
sample water from .25 m, 1 m, and 2 m was preserved with 1mL of Acid Lugol’s for
potential later use.
2.4 Population Counts
Slides were prepared for population counts of dinoflagellates at each depth
according to the following procedure. 2-3 mL of previously concentrated sample was
filtered onto an 8 µm-nitrocellulose filter. Filters were dried briefly on top of an
upside down petri dish that was placed on a hotplate set to the lowest heat setting. 2-
3 drops of immersion oil were placed on a microscope slide, and the filter was placed
on top of the immersion oil. The filters cleared upon contact with the immersion oil.
A cover slip was placed on each slide and all slides were refrigerated until counted.
Counting was performed using a Jena-Lumar© light microscope. All counts
were made at 125X magnification. Two different counting methods were employed
depending on the abundance of organisms. If few dinoflagellates were present, then
slides were counted by two transects across the diameter of the filter: one horizontal
and one vertical. The width of one transect was the width of the eyepiece grid at
125X magnification (790 µm). When many dinoflagellates were present, the slides
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were counted by random fields. Counts were made in ten random fields giving a total
number of organisms per the area of 10 fields (each field was 0.624 mm2). Slide
counts and concentration factors for each sample were used to back-calculate the
population density of all dinoflagellates. Estimates of actual densities (given in
cells /L) were made using the following formula:
# of cells counted X area of filter (mm2) X Concentration Factor area counted (mm2) mL filtered
where the area counted was equal to 0.6241 mm2 per field x 10 fields = 6.241 mm2 or
when transects were used, the length x width of a transect. The area of the filter was
227 mm2. The concentration factor was given by:
volume of sample after concentrating (L)
volume of field sample concentrated (L)
2.5 Species Identification and Population Proportion Counts using SEM
In order to identify species of dinoflagellates, scanning electron microscopy
was used to visualize the morphological features used to classify freshwater
dinoflagellates. Dinoflagellates were identified by the number and pattern of thecal
plates and also by the presence of reticulation on thecal plates. Species were
identified using three taxonomical keys to the freshwater dinoflagellates (Popovsky
1990; Starmach 1974; Lefevre 1932).
Scanning electron microscope stubs were prepared by filtering between 2 and
5 mL of concentrated sample water (see section 2.3) onto a 0.8µm-membrane filter.
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The filter was dried by the same method as section 2.5. After drying, filters were
affixed to the stubs using double-sided tape and gold coated using a sputter coater.
The specimens were examined using a JEOL® JSM-5600 scanning electron
microscope. The magnification was changed as needed to examine morphological
features.
In addition to identification of species present in the water samples, scanning
electron microscopy was employed to estimate the proportion of the total
dinoflagellate population contributed by each species throughout the 16 month
sampling period. SEM stubs were prepared by the same method used for species
identification for two sampling dates from each month. For each date, stubs were
prepared from all three sampled depths (.25 m, 1 m, 2 m). Relative abundances were
determined by counting a series of transects across the stub until 100 cells were
counted. All counts were made at 300X magnification. The percent of total
dinoflagellates represented by each species was multiplied by the total density
obtained from the light microscope counts (see section 2.4) in order to estimate
individual species densities on each sampling date.
2.6 Dissolved Inorganic Nutrient Measurements Ion chromatography was used to quantify dissolved inorganic nutrients. In
particular, concentrations of nitrate, orthophosphate, and ammonium were measured
to estimate trophic status of the lake. Measurements of sulfate were also made.
Filtrate from the GF/F-filters (see section 2.3) was analyzed on a Dionex® 600
system with an AS14 column and conductivity detector. Peaknet® 6 software was
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used for analysis. The detection limits were 10 ppb for nitrate and phosphate. The
detection limits for ammonium and sulfate were 5 ppb and 3 ppb, respectively.
2.7 Pigment Measurements using HPLC
High performance liquid chromatography (HPLC) was used to quantify
pigments from the GF/F-filters (see section 2.3). Chlorophyll a was quantified to
estimate total phytoplankton biomass. Peridinin was quantified because it is a
pigment unique to dinoflagellates. Sample preparations were performed after the
method of Wright and Jeffrey (1997). The filters were extracted with 5 mL of 90%
acetone, sonicated, and the resulting pulp was filtered again using centrifugation.
Samples were run using a Dionex® reversed phase HPLC column with both UV-Vis
and photodiode array detectors. Chromeleon® software was used for data analysis.
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Section 3: Physical and Chemical Characteristics of Boondoggle Lake
This section presents the physical and chemical data recorded over the study
period, including measurements of temperature, dissolved oxygen, pH, Secchi depth,
dissolved inorganic ions, and photosynthetic pigments.
3.1 Temperature
Throughout the study period, water surface temperatures ranged from 7.5 to
310 C, with an average of value of 210 C. Vertical temperature profiles show that the
lake has well defined temperature stratification that lasts throughout the summer
months. It mixes completely during the remainder of the year and rarely, if ever,
experiences ice cover. Therefore, according to the classification scheme of Lewis
(1983), Boondoggle Lake is a warm monomictic lake (Kalff 2002).
Figure 3.1 presents temperature profiles for selected dates from each month
sampled. For the profiles from 2002, stratification began in March, and the
thermocline remained poorly defined through April and May. In June, a well defined
thermocline was seen beginning at 1.5 m. By October, the lake was mixing again.
A similar trend was seen in the 2003 temperature profiles. The lake began to
stratify in March and showed weak stratification from April through May. A well
defined thermocline was seen in June and July.
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Mar
ch 2
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002
O2
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: Tem
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and
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sele
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dat
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egin
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Mar
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Figu
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.1 (c
ontin
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Mar
ch 1
5, 2
003
O2
(mg/
L)
24
68
1012
Depth
0 1 2 3 4
Tem
p (C
)5
1015
2025
30
Apr
il 17
, 200
3
O2
(mg/
L)
24
68
1012
0 1 2 3 4
Tem
p (C
)5
1015
2025
30
May
20,
200
3
O2
(mg/
L)
24
68
1012
0 1 2 3 4
Tem
p (C
)5
1015
2025
30
June
24,
200
3
O2
(mg/
L)
24
68
1012
Depth
0 1 2 3 4
Tem
p (C
)
510
1520
2530
July
10,
200
3
O2
(mg/
L)
24
68
1012
0 1 2 3 4
Tem
p (C
)
510
1520
2530
O2
Tem
p
Figu
re 3
.1 (c
ontin
ued)
20
3.2 Dissolved Oxygen
A stratification of dissolved oxygen levels accompanied temperature
stratification in the summer. Anoxic conditions were present during the summer
months, which began near the lake bottom and rose to depths just below the
epilimnion.
Dissolved oxygen in surface waters (0.25 m) ranged from 6 mg/L to
11.5 mg/L during the study period. When the lake was mixing, dissolved oxygen
was between 7-10 mg/L at all depths.
Figure 3.1 presents dissolved oxygen profiles for selected dates from each
month sampled. In 2002, stratification of dissolved oxygen began in mid April,
and by mid May, anoxia developed below 4 m. The depth at which anoxia began
became shallower during June and July and receded during August and
September. The shallowest depth at which anoxia began was recorded on August
22, 2002 and was 1.25 m. By October, the lake was mixing and the dissolved
oxygen concentration was approximately 6 mg/L. Dissolved oxygen increased
during the colder winter months, reaching a maximum of 10 mg/L in December.
Data from 2003 showed a similar trend in dissolved oxygen concentration.
Again, strong stratification and anoxia began in May. In the profiles from June
and July, oxygen concentration dropped quickly after a depth of 1 m, with
complete anoxia occurring between 1.25 m and 1.5 m.
21
3.3 pH
For all dates and depths, pH was always between 5.5 and 6.5. Figure 3.2
shows the temporal changes in pH values measured at three depths. The data
suggest a stratification of pH that corresponds to the temperature and oxygen
stratification mentioned in sections 3.1 and 3.2.
In Figure 3.2, from May 2002 through September 2002, a clear separation
was seen between the pH values of each depth. The pH measured at .25 m
remained the highest and the pH measured at 2 m remained the lowest through the
stratification period, with the pH at 1 m falling in between. This pattern of
decreasing pH with depth is likely due to buildup of carbon dioxide and carbonic
acid associated with anoxia at deeper depths. Measurements of pH remained
similar between depths during lake mixing (October 2002- April 2003).
3.4 Secchi Depth
Figure 3.3 shows temporal patterns in Secchi depth. Secchi depth ranged
from 2.1 m in the early spring to 0.72 m in late summer. Average Secchi depth
was 1.2 m over the study period.
The major pattern observed in Secchi depth was the sharp decrease in
early June to a depth of approximately 1 m. Secchi depth then gradually
decreased through the summer and remained shallow until November, when a
sharp increase in depth occurred.
22
Dat
e
27-M
ar-02 5-A
pr-02
12-A
pr-02
21-A
pr-02
26-A
pr-02 2-M
ay-02
10-M
ay-02 15
-May
-02 26-M
ay-02 2-J
un-02 7-J
un-02 14
-Jun-0
221
-Jun-0
228
-Jun-0
212
-Jul-0
226
-Jul-0
229
-Aug
-02 6-Sep
-02 13-S
ep-02 20
-Sep
-02 27-S
ep-02 7-Oct-
0218
-Oct-
0225
-Oct-
02 8-Nov
-02 22-N
ov-02 6-D
ec-02 9-J
an-03 21
-Feb
-03 27-F
eb-03 6-M
ar-03
15-M
ar-03
21-M
ar-03
30-M
ar-03 5-A
pr-03
17-A
pr-03
25-A
pr-03 1-M
ay-03 20
-May
-03 11-Ju
n-03
24-Ju
n-03
10-Ju
l-03
4-Sep
-03
pH
5.0
5.1
5.2
5.3
5.4
5.5
5.6
5.7
5.8
5.9
6.0
6.1
6.2
6.3
6.4
6.5
6.6
.25m
1m 2m
Figu
re 3
.2: T
empo
ral p
atte
rns o
f pH
for t
hree
dep
ths:
.25m
, 1m
, and
2m
23
Sec
chi D
epth
Dat
e
27-Mar-02 5-Apr-02 12-Apr-02 21-Apr-02 26-Apr-02 2-May-0210-May-0215-May-0226-May-02 2-Jun-02 7-Jun-0214-Jun-0228-Jun-02 12-Jul-02 26-Jul-0222-Aug-0229-Aug-02 6-Sep-0213-Sep-0220-Sep-0227-Sep-02 7-Oct-02 18-Oct-02 25-Oct-02 8-Nov-0222-Nov-02 6-Dec-02 9-Jan-0321-Feb-0327-Feb-03 6-Mar-0315-Mar-0321-Mar-0330-Mar-03 5-Apr-03 17-Apr-03 25-Apr-03 1-May-0320-May-0311-Jun-0324-Jun-03 10-Jul-03 4-Sep-03
Depth (m)0.0
0.5
1.0
1.5
2.0
2.5
Figu
re 3
.3: T
empo
ral p
atte
rns i
n Se
cchi
dep
th
24
3.5 Dissolved Inorganic Ions
Table 3.1 presents monthly measurements of nitrate, phosphate,
ammonium, and sulfate for samples from each depth between May 2002 and
March 2003. Entries labeled “ND” represent ion concentrations below the
detection limit (see section 2.7).
Nitrate concentrations were higher in the fall and winter, and were highest
in February (0.12- 0.15 ppm). An average concentration of 0.16 ppm was
recorded in the surface samples from June. Orthophosphate concentrations
remained under the detection limit from June 2002 – September 2002. The
highest concentrations were recorded in fall and spring (0.15- 0.20 ppm). The
highest ammonium concentrations were recorded in September, October, and
November 2002. The highest sulfate concentrations were recorded in winter and
spring.
3.6 Photosynthetic Pigments (chlorophyll a and peridinin)
Table 3.2 presents monthly measurements of chlorophyll a and peridinin
for samples from each depth between June 2002 and February 2003. Entries
labeled “ND” represent samples where the pigment was not detected.
Chlorophyll a concentrations ranged from 0.8- 8.6 ppb, with the highest
concentrations occurring in the summer and fall. Peridinin concentrations were
highest in July, August, and September (1.37- 9.39 ppb). Peridinin was either
detected in low concentrations or not detected in the fall and winter samples.
25
NO
3 (p
pm)
P
O4
(ppm
)
N
H4
(ppm
)
SO4
(ppm
)
.25m
1m2m
.25m
1m2m
.2
5m1m
2m.2
5m1m
2mM
onth
n
May
-02
1 0.
07
ND
0.05
0.
06N
DN
D0.
150.
090.
081.
861.
751.
78Ju
n-02
3
0.16
ND
ND
ND
ND
ND
0.14
0.10
0.07
1.67
1.51
1.97
Jul-0
2 2
ND
ND
0.01
ND
ND
ND
0.12
0.07
0.19
1.05
1.10
1.40
Aug
-02
1N
DN
DN
DN
D0.
190.
150.
920.
17S
ep-0
2 2
ND
0.07
0.04
ND
ND
ND
0.22
0.28
0.42
1.00
1.10
1.16
Oct
-02
10.
020.
030.
09N
DN
D0.
150.
100.
211.
121.
291.
360.
34N
ov-0
2 1
0.15
0.02
ND
0.20
ND
ND
3.94
0.24
0.29
0.86
1.25
1.27
Dec
-02
10.
030.
04N
DN
D0.
090.
191.
531.
56Ja
n-03
10.
030.
020.
040.
05N
DN
D0.
070.
120.
121.
761.
711.
79Fe
b-03
1
0.12
0.15
0.15
0.05
ND
ND
0.15
0.07
ND
2.23
2.28
2.27
Mar
-03
20.
03N
DN
D0.
15N
DN
D0.
150.
130.
161.
962.
022.
13
T
able
3.1
: Mon
thly
mea
sure
men
ts o
f nitr
ate,
pho
spha
te, a
mm
oniu
m, a
nd su
lfate
con
cent
ratio
ns.
Val
ues f
or m
onth
s with
mor
e th
an
one
mea
sure
men
t (n>
1) h
ave
been
ave
rage
d.
26
Chlorophyll a (ppb) Peridinin (ppb) Month n 0.25 1 2 0.25 1 2
Jun-02 5 1.32 1.45 2.36 1.01 1.00 0.93 Jul-02 2 2.04 1.61 8.56 2.66 2.67 9.39 Aug-02 2 1.71 1.91 3.07 1.67 2.63 4.40 Sep-02 4 3.70 1.75 1.19 4.32 1.37 3.01 Oct-02 2 3.26 4.47 2.67 1.03 1.07 0.60 Nov-02 1 1.48 3.11 1.33 ND 0.30 ND Dec-02 1 1.52 2.60 1.96 0.26 0.67 0.23 Jan-03 1 1.39 0.14 1.47 ND ND ND Feb-03 1 0.83 1.86 1.76 ND ND ND
Table 3.2: Monthly measurements of chlorophyll a and peridinin concentration. Values for months with more than one measurement have been averaged.
27
Section 4: Identification of Dinoflagellate Species from Boondoggle Lake
Six species of freshwater armored dinoflagellates were identified from the
water samples taken from Boondoggle Lake. They include Peridinium deflandrei,
Peridinium volzii, Peridinium wisconsinense, Peridinium limbatum, Peridinium
inconspicuum, and Peridiniopsis polonicium. This section highlights the main
morphological features that are unique to each species, and presents data on cell size
and geographical distribution.
4.1 Peridinium deflandrei
P. deflandrei belongs to the subgenus Poroperidinium, meaning it possesses
an apical pore. The general epithecal plate formula for this subgenus according to the
Kofoid system of plate designation is 4/, 3a, 7// (Taylor 1987; Popovsky and Pfiester
1990). However, P. deflandrei has the epithecal plate formula of 4/, 2a, 7// (Popovsky
and Pfiester 1990). Popovsky and Pfiester (1990) classify this species as Peridinium
umbonatum var. deflandrei, grouping it with a number of other species. The
taxonomic schemes of Lefevré (1932) and Starmach (1974) have it listed as a
separate species, Peridinium deflandrei.
Distinguishing features used to positively identify P. deflandrei included
epithecal plate pattern, absence of reticulation on thecal plates, presence of rows of
28
small points on thecal plates, and two antapical spines (Popovsky and Pfiester 1990;
Lefevré 1932, Starmach 1974).
Vegetative cells of P. deflandrei are between 28-35 µm long and 26-32 µm
wide. This species has been reported in Spain and in New York (Lefevré 1932;
CSLAP 2002).
Scanning electron micrographs of P. deflandrei are presented on Plate 4.1.
4.2 Peridinium volzii
P. volzii is the only Peridinium species in this study belonging to the subgenus
Cleistoperidinium. This subgenus name has now been changed to Peridinium and
includes all Peridinium species lacking an apical pore (Popovsky and Pfiester 1990;
Carty 1986). The general epithecal plate formula for this subgenus according to the
Kofoid system of plate designation is 4/, 3a, 7// (Taylor 1987; Popovsky and Pfiester
1990).
Distinguishing features used to positively identify P. volzii included
symmetrical arrangement of the three intercalary plates, a small 1/ plate, sulcal
penetration into the epitheca, and reticulation on the thecal plates (Carty 1986; Susan
Carty pers. Comm.).
P. volzii vegetative cells are between 38-42 µm long and wide. It has been
previously reported in the United States in Oklahoma, North Carolina, Minnesota,
Maryland, and Massachusetts. It has also been reported in Canada, Australia, Europe,
Asia, and Africa (Carty 1986).
Scanning electron micrographs of P. volzii are presented on Plate 4.2.
29
4.3 Peridinium wisconsinense
P. wisconsinense belongs to the subgenus Poroperidinium. Cells of this
species are pointed at each end, giving them a spindle shape. The two bottom plates
on the hypotheca (1//// and 2////) form a horn-like structure, with the 1//// plate extending
to the tip of this structure. The sulcus only penetrates slightly into the epitheca, and
reticulation is present on the thecal plates (Carty 1986; Popovsky and Pfiester 1990).
These features were used to positively identify P. wisconsinense.
Vegetative cells of P. wisconsinense are between 55-64 µm long and 48-56
µm wide (Popovsky and Pfiester 1990). It has previously been reported in the United
States and Canada. Within the United States, there have been reports from Alabama,
Georgia, Louisiana, Massachusetts, Michigan, Minnesota, New Jersey, North
Carolina, South Carolina, Texas, West Virginia, and Wisconsin (Carty 1986).
Scanning electron micrographs of P. wisconsinense are presented on Plate 4.3.
4.4 Peridinium limbatum
P. limbatum belongs to the subgenus Poroperidinium. The most distinctive
features of this species are the pair of horn-like thecal projections on the hypotheca
and the conical, pointed epitheca. The sulcus widens on the hypotheca and reaches
the antapex of the cell. Reticulation is present on the thecal plates (Popovsky and
Pfiester 1990).
P. limbatum is the largest species identified in this study. Vegetative cells are
between 80-93 µM long and 60-82 µm wide (Popovsky and Pfiester 1990). An
30
incomplete list of where it has been documented includes Canada and Oklahoma
(Holt 1981; Yan and Stokes 1978; Yung 1991).
Scanning electron micrographs of P. limbatum are presented on Plate 4.4.
4.5 Peridinium inconspicuum
P. inconspicuum belongs to the subgenus Poroperidinium and is recognized
by its small size as well as shape. The cingulum divides the epitheca into almost
equal halves, and the sulcus penetrates slightly into the epitheca. There is no
reticulation on the thecal plates, but there is ornamentation in the form of longitudinal
rows of dots. Spines may be found on the antapex (Carty 1986). These features,
along with the expertise of Dr. Susan Carty, were used to identify P. inconspicuum
(Susan Carty pers. comm.).
P. inconspicuum is the smallest freshwater dinoflagellates species, with
vegetative cells ranging from 15-30 µm long and 12-25µm wide. It is a widely
reported species. Reports come from most European countries, Cuba, and the United
States. Within the United States, it has been reported in 25 states, including
Mississippi. The range within the continental United States includes far western
(California) to eastern (South Carolina) and southern (Mississippi, Louisiana) to
northern (Wisconsin, North Dakota) (Carty 1986).
Scanning electron micrographs of P. inconspicuum are presented on Plate 4.5.
31
4.6 Peridiniopsis polonicium
The genus Peridiniopsis is distinguished from Peridinium because species
possess 0-1 anterior intercalary plates. Peridiniopsis polonicium was identified by its
oval shape, large 1/ plate, reticulation on thecal plates, and sulcal extension to the
antapex (Popovsky and Pfiester 1990). Identification was also confirmed with Dr.
Susan Carty (Susan Carty pers. comm.). Variations are known to occur in the number
of anterior intercalary plates in this species, and cells observed in this study had two
anterior intercalary plates (Popovsky and Pfiester 1990).
Vegetative cells of Peridiniopsis polonicium are between 33-54 µm long and
30-51 µm wide. Areas where this species has been documented include Europe and
North America (Popovsky and Pfiester 1990).
Scanning electron micrographs of Peridiniopsis polonicium are presented on
Plate 4.5.
4.7 Other Phytoplankton and Zooplankton
Other phytoplankton identified included cryptomonads, diatoms, green algae,
and the chrysophyte Dinobryon. Although it was not quantified, Dinobryon was
found in high densities in the spring. This alga is phagotrophic and feeds on bacteria
(Graham and Wilcox 2000). Scanning electron micrographs of diatoms are presented
on Plate 4.6. Scanning electron micrographs of Dinobryon and the green alga
Micrasterias are presented on Plate 4.7.
The zooplankton identified included rotifers, cladocerans, and copepods. A
scanning electron micrograph of a Keratella rotifer is included on Plate 4.7.
32
Plate Legend Plate 4.1 a. P. deflandrei ventral view………………………………………………....34 b. P. deflandrei epitheca..................................................................................34 Plate 4.2 a. P. volzii ventral view…………………………………………………........35 b. P. volzii epitheca..........................................................................................35 Plate 4.3 a. P. wisconsinense dorsal view………………………………………...……36 b. P. wisconsinense side view………………………………………………..36 Plate 4.4 a. P. limbatum ventral view………………………………………………….37 b. P. limbatum (dorsal) and P. volzii epitheca……………………………….37 Plate 4.5 a. Peridiniopsis polonicium ventral view………………………………..….38 b. P. inconspicuum dorsal view …………………………………………….38 Plate 4.6 Diatoms…………………………………………………………………..…39 Plate 4.7 a. The green alga Micrasterias……………………………………………..40 b. A rotifer, Keratella………………………………………………………40 c. The chrysophyte Dinobryon…………………………………………..…40
33
Plate 4.1
a
b
34
Plate 4.2
a
b
35
Plate 4.3
a
b
36
Plate 4.4
a
b
37
Plate 4.5
a
b
38
Plate 4.6
39
Plate 4.7
a
b
c
40
Section 5: Spatial and Temporal Patterns in Population for Dinoflagellates in Boondoggle Lake
This section presents the results of the counts of total dinoflagellate abundance,
and for five of the six species identified, population proportion of species and estimates
of population sizes for individual species are presented. One species, Peridinium
inconspicuum, could not be quantified because it is smaller than the size of the mesh used
to concentrate the water samples (see methods, section 2.3).
5.1 Total Dinoflagellate Abundance
The temporal changes in combined population density for all dinoflagellates greater
than 20 µm in size is shown for each depth sampled in Figure 5.1. It should be noted that
the X-axis is not to scale.
Maximum population densities occurred between July 26 and September 13, 2002
for all three depths. The maximum population density for 0.25 m occurred on August 22,
2002 and was 2 X 105 cells/L. The maximum density recorded for 1 m occurred two
weeks later on September 6 and was 2.96 X 105 cells/L. For the 2 m samples, the
maximum density occurred on September 13, 2002 and was 1.78 X 105 cells/L.
In addition to the summer maxima, other smaller peaks of density occurred. At
0.25 m, there were two small peaks, one two months before and one a month after the
main summer maximum. These peaks were between 5-7 X 104 cells/L. Two peaks
41
0
50000
100000
150000
200000
250000
300000
.25 MC
ells
/L
0
50000
100000
150000
200000
250000
300000
1M
5-Ap
r-02
12-A
pr-0
221
-Apr
-02
26-A
pr-0
22-
May
-02
10-M
ay-0
215
-May
-02
26-M
ay-0
22-
Jun-
027-
Jun-
0214
-Jun
-02
21-J
un-0
228
-Jun
-02
12-J
ul-0
226
-Jul
-02
22-A
ug-0
229
-Aug
-02
6-Se
p-02
13-S
ep-0
220
-Sep
-02
27-S
ep-0
27-
Oct
-02
18-O
ct-0
225
-Oct
-02
8-No
v-02
22-N
ov-0
26-
Dec-
029-
Jan-
0321
-Feb
-03
27-F
eb-0
315
-Mar
-03
30-M
ar-0
317
-Apr
-03
20-M
ay-0
311
-Jun
-03
0
50000
100000
150000
200000
250000
300000
2M
Date
Figure 5.1: Total dinoflagellate population density
42
between 6-8 X 104 cells/L were seen in the spring at 1 m. Also at 1 m, a peak in June of
1.2 X 105 cells/L and a peak in October of 7 X 104 cells/L were seen.
5.2 Population Proportion
Figures 5.2-5.4 show the patterns in proportion of the total population for each
species at all dates and depths sampled. Clear temporal patterns of population proportion
were observed for all species. However, no clear differences in population proportion
were seen between sample depths.
Individual species showed one of two temporal patterns in percent of the total
population. The first pattern was a higher percentage in the summer and fall, and the
second pattern was a higher percentage in the winter and spring. P. deflandrei, P.
wisconsinense, and Peridiniopsis polonicium all were a higher percentage of the total
population between mid-May and mid-November. P. volzii and P. limbatum were all a
higher percentage between November and April.
The two species that represented the highest proportion at all three depths and for
all dates sampled were P. deflandrei and P. volzii. None of the other three species ever
comprised more than 25 % of the total dinoflagellate abundance. P. deflandrei was 50%
or more of the total dinoflagellates on approximately 63% of the days sampled, especially
in the summer and early fall. P. volzii was 50% or more of the dinoflagellates on
approximately 32% of the days sampled, especially in the late fall, winter, and spring.
Since P. volzii occurs in the winter and spring when total dinoflagellates abundance is
low, its high proportion at these times does not necessarily mean it has a high population
43
P. deflandrei
0
25
50
75
100
P. volzii
0
25
50
75
100
P. limbatum
Perc
ent o
f Tot
al D
inof
lage
llate
s
0
25
50
75
100
P. wisconsinense
0
25
50
75
100
Peridiniopsis polonicium
12-A
pr-02
26-A
pr-02
15-M
ay-02
2-Jun-02
14-Ju
n-02
28-Ju
n-02
12-Ju
l-02
26-Ju
l-02
22-A
ug-02
29-A
ug-02
6-Sep
-02
13-S
ep-02
27-S
ep-02
18-O
ct-02
25-O
ct-02
8-Nov-0
2
22-N
ov-02
6-Dec
-02
9-Jan
-03
21-Feb
-03
15-M
ar-03
30-M
ar-03
17-A
pr-03
1-May
-03
20-M
ay-03
11-Ju
n-03
24-Ju
n-030
25
50
75
100
Date
Figure 5.2: Population proportion at 0.25 m
44
P. deflandrei
0
25
50
75
100
P. volzii
0
25
50
75
100
P. limbatum
Perc
ent o
f Tot
al D
inof
lage
llate
s
0
25
50
75
100
P. wisconsinense
0
25
50
75
100
Peridiniopsis polonicium
12-A
pr-02
26-A
pr-02
15-M
ay-02
2-Jun-02
14-Ju
n-02
28-Ju
n-02
12-Ju
l-02
26-Ju
l-02
22-A
ug-02
29-A
ug-02
6-Sep
-02
13-S
ep-02
27-S
ep-02
18-O
ct-02
25-O
ct-02
8-Nov-0
2
22-N
ov-02
6-Dec
-02
9-Jan
-03
21-Feb
-03
15-M
ar-03
30-M
ar-03
17-A
pr-03
1-May
-03
20-M
ay-03
11-Ju
n-03
24-Ju
n-030
25
50
75
100
Date
Figure 5.3: Population proportion at 1 m
45
P. deflandrei
0
25
50
75
100
P. volzii
0
25
50
75
100
P. limbatum
Per
cent
of T
otal
Din
ofla
gella
tes
0
25
50
75
100
P. wisconsinense
0
25
50
75
100
Peridiniopsis polonicium
12-A
pr-02
26-A
pr-02
15-M
ay-02
2-Jun-02
14-Ju
n-02
28-Ju
n-02
12-Ju
l-02
26-Ju
l-02
22-A
ug-02
29-A
ug-02
6-Sep
-02
13-S
ep-02
27-S
ep-02
18-O
ct-02
25-O
ct-02
8-Nov-0
2
22-N
ov-02
6-Dec
-02
9-Jan
-03
21-Feb
-03
15-M
ar-03
30-M
ar-03
17-A
pr-03
1-May
-03
20-M
ay-03
11-Ju
n-03
24-Ju
n-030
25
50
75
100
Date
Figure 5.4: Population proportion at 2 m (circles represent no data)
46
density. P. deflandrei, however, reaches a maximum proportion of the population in the
summer when total density is high and is responsible for 90% of the summer maximum.
5.3 Individual Population Trends
Calculated estimates of population density for each species over the sampling
period are shown in Figures 5.5-5.7. Y-axes are scaled differently for each species in
order to clearly show trends in population density. The X-axis is not to scale.
Peridinium deflandrei showed a temporal pattern in population density almost
identical to the total abundance of dinoflagellates because it was such a high percentage
of the dinoflagellate assemblage in the summer. Spatial and temporal patterns were seen
in this summer bloom of P. deflandrei that suggested rapid initial growth followed by the
sinking of the bloom. A sharp increase in population at 0.25 m was seen beginning in
July 2002, and an initial maximum density of 1.6 X 105 cells/L occurred at 0.25 m in late
August (see Figure 5.5). By the beginning of September, a maximum density of 2.75 X
105 cells/L was observed at 1 m, accompanied by an 80% decrease in density at 0.25 m
(see Figures 5.5 and 5.6). The maximum at 1 m decreased 98% by mid September, at
which time a maximum of 1.75 X 105 cells/L was seen at 2 m (see Figure 5.7).
Peridinium volzii had maximum densities mostly in the spring. At 0.25 m, it had
a maximum density of 2 X 104 cells/L in April 2002 and another peak of 1.2 X 104
cells/L in August 2002 (see Figure 5.5). At 1 m, a maximum of 5.7 X 104 cells/L
occurred in April 2002. This high density was not seen in samples from April 2003 (see
Figure 5.6). At 2 m, clear peaks were seen in population density in mid to late April for
2002 and 2003 (see Figure 5.7). These peaks were between 2.2 - 2.8 X 104 cells/L.
47
P. deflandrei
0
60000
120000
180000
P. volzii
0
10000
20000
30000
P. limbatum
Cel
ls/ L
0
1000
2000
3000
4000
5000
P. wisconsinense
0
10000
20000
30000
Peridiniopsis polonicium
12-A
pr-02
26-A
pr-02
15-M
ay-02
2-Jun
-02
14-Ju
n-02
28-Ju
n-02
12-Ju
l-02
26-Ju
l-02
22-A
ug-02
29-A
ug-02
6-Sep
-02
13-S
ep-02
27-S
ep-02
18-O
ct-02
25-O
ct-02
8-Nov
-02
22-N
ov-02
6-Dec
-02
9-Jan
-03
21-F
eb-03
15-M
ar-03
30-M
ar-03
17-A
pr-03
20-M
ay-03
11-Ju
n-03
0
10000
20000
30000
Date
Figure 5.5: Individual population trends at 0.25 m
48
P. deflandrei
0
60000
120000
180000
240000
300000
P. volzii
0
20000
40000
60000
P. limbatum
Cel
ls/ L
0
1000
2000
3000
4000
5000
P. wisconsinense
0
10000
20000
30000
Peridiniopsis polonicium
12-A
pr-02
26-A
pr-02
15-M
ay-02
2-Jun
-02
14-Ju
n-02
28-Ju
n-02
12-Ju
l-02
26-Ju
l-02
22-A
ug-02
29-A
ug-02
6-Sep
-02
13-S
ep-02
27-S
ep-02
18-O
ct-02
25-O
ct-02
8-Nov
-02
22-N
ov-02
6-Dec
-02
9-Jan
-03
21-F
eb-03
15-M
ar-03
30-M
ar-03
17-A
pr-03
20-M
ay-03
11-Ju
n-03
0
1000
2000
3000
4000
5000
Date
Figure 5.6: Individual population trends at 1 m
49
P. deflandrei
0
60000
120000
180000
P. volzii
0
10000
20000
30000
P. limbatum
Cel
ls/ L
0
1000
2000
3000
4000
5000
P. wisconsinense
0
1000
2000
3000
4000
5000
Peridiniopsis polonicium
12-A
pr-02
26-A
pr-02
15-M
ay-02
2-Jun
-02
14-Ju
n-02
28-Ju
n-02
12-Ju
l-02
26-Ju
l-02
22-A
ug-02
29-A
ug-02
6-Sep
-02
13-S
ep-02
27-S
ep-02
18-O
ct-02
25-O
ct-02
8-Nov
-02
22-N
ov-02
6-Dec
-02
9-Jan
-03
21-F
eb-03
15-M
ar-03
30-M
ar-03
17-A
pr-03
20-M
ay-03
11-Ju
n-03
0
1000
2000
3000
4000
5000
Date
Figure 5.7: Individual population trends at 2 m (circles represent no data)
50
Peridinium limbatum stayed at relatively low population densities throughout the
sampling period. At both 0.25 m and 1 m, a peak in population density was seen in late
April with a density of approximately 2 X 103 cells/L (see Figure 5.5 and 5.6). At 1 m,
another peak of 2.5 X 103 cells/L was seen in mid March (see Figure 5.6). P. limbatum
never reached a density higher than 300 cells/L in the 2 m samples.
Peridinium wisconsinense reached maximum population densities in the late
summer. At 0.25 m, maximum density occurred in August and was 1 X104 cells/L (see
Figure 5.5). The maximum population density at 1 m occurred in September and was 2.1
X 104 cells/L (see Figure 5.6). Densities at 2 m were low for P. wisconsinense. The
highest density at 2 m occurred in late July and was 5 X 103 cells/L (see Figure 5.7).
Peridiniopsis polonicium was only found at high density in the summer and in the
surface water. The maximum density at 0.25 m occurred in August and was 1.6 X 104
cells/L (see Figure 5.5). At 1 m, the density was low except in July, when it was 3 X 103
cells/L (see Figure 5.6). At 2 m, a maximum of 3.5 X 103 cells/L occurred in mid
September.
5.4 Correlations Between Temperature and Population Density
Correlations between dinoflagellate population density and temperature are
presented in Figures 5.8 and 5.9. Figure 5.8 shows the correlation of total dinoflagellate
density to temperature for each sampling depth through the entire sampling period.
Figure 5.9 shows the correlation of the most abundant dinoflagellate, P. deflandrei, to
temperature for each sample depth through the entire sampling period.
51
For the total dinoflagellate density, a positive correlation between density and
temperature was seen at all three depths. This correlation was stronger for samples from
1 m (r2= 0.61) than for samples from 0.25 m and 2 m (r2= 0.40 and 0.34, respectively).
P. deflandrei density was also positively correlated with temperature at all three
sample depths. This correlation was slightly stronger for samples from 0.25 m (r2= 0.70)
and 2 m (r2= 0.77) than for samples from 1 m (r2= 0.67).
52
Total Dinoflagellates (.25m)
R2 = 0.40
0.000
1.000
2.000
3.000
4.000
5.000
6.000
0 5 10 15 20 25 30Temperature
Log
Cel
ls/L
Total Dinoflagellates (1m)
R2 = 0.61
0.000
1.000
2.000
3.000
4.000
5.000
6.000
0 5 10 15 20 25 30
Temperature
Log
Cel
ls/L
Total Dinoflagellates (2m)
R2 = 0.34
0.000
1.000
2.000
3.000
4.000
5.000
6.000
0 5 10 15 20 25 30
Temperature
Log
Cel
ls/L
Figure 5.8: Correlation of total dinoflagellate density to temperature
53
P. deflandrei (.25m)
R2 = 0.70
0.0
1.0
2.0
3.0
4.0
5.0
6.0
0.0 10.0 20.0 30.0
Temperature
Log
Cel
ls/L
P. deflandrei (1m)
R2 = 0.67
0.0
1.0
2.0
3.0
4.0
5.0
6.0
0.0 5.0 10.0 15.0 20.0 25.0 30.0
Temperature
Log
Cel
ls/L
P. deflandrei (2m)
R2 = 0.77
0.0
1.0
2.0
3.0
4.0
5.0
6.0
0.0 5.0 10.0 15.0 20.0 25.0 30.0
Temperature
Log
Cel
ls/ L
Figure 5.9: Correlation of P. deflandrei density to temperature
54
Section 6: Discussion Dinoflagellates have potentially large roles in freshwater ecosystems, yet there is
still a paucity of information on the ecology of freshwater dinoflagellates. Many studies
of dinoflagellate ecology have been conducted in areas other than the United States.
Information on dinoflagellate diversity and abundance is especially lacking in the
southeastern United States.
To my knowledge, all species identified in this study, with the exception of P.
inconspicuum, have not been previously reported in Mississippi. There seems to be little
information on the distribution of P. deflandrei. Lefevré (1932) reported this species in
Spain, and a report from Echo Lake in New York was the only occurrence I could find in
the United States (CSLAP 2002). P. volzii is a cosmopolitan species, with reports from
the southeastern, northeastern, and midwestern United States, and it has also been
reported in Europe, Asia, Africa, and Austrailia (Carty 1986; Starmach 1974; Lefevré
1932). Given this information, it is not surprising that it is also found in Mississippi. P.
limbatum has been reported mostly in Canada, but one report comes from Oklahoma
(Holt 1981; Yan and Stokes 1978, Yung 1991). To my knowledge, this is the furthest
south P. limbatum has been identified. P. wisconsinense is a common species in the
eastern United States. It has been documented in at least 11 states, including two that
border Mississippi (Carty 1986). Peridiniopsis polonicium may also be a cosmopolitan
species since it has been documented in Europe, North America, and Japan (Popovsky
and Pfiester 1990; Hashimoto et. al. 1968).
55
By far, the dominant species of dinoflagellate in the summer bloom in
Boondoggle Lake is P. deflandrei. This species comprised an average of 90% of the total
dinoflagellates during the bloom period that began in June and ended in September. The
shift in the population density maximum from 0.25 m in late August to 1 m in early
September and to 2 m in mid September suggests that the bloom formed in the surface
waters and moved downward. Whether this downward movement was due to migration
or sinking is unclear.
P. volzii was the second most abundant species of dinoflagellate in Boondoggle
Lake. However, the maximum density observed for P. volzii was only 20% of the size of
maximum density for P. deflandrei. P. volzii also had a different temporal pattern in
abundance than P. deflandrei; larger populations were observed in months with cooler
temperatures. This pattern is consistent with a previous study that found population
maxima of P. volzii at temperatures between 170 C and 210 C (Olrik 1992). In this study,
P. volzii reached maximum densities in March and April, was mostly absent in the
summer, and was at low densities (< 5000 cells/L) from October through December. One
exception to this pattern was a summer peak of P. volzii at 0.25 m on August 22 (see
Figure 5.5). On this date, water temperature at 0.25 m was 250 C, about 5 degrees cooler
than measurements before and after, which may account for the brief summer peak of P.
volzii.
The other three species exhibited a temporal pattern similar to either P. deflandrei
or P. volzii. P. limbatum was most abundant in the spring and fall. P. wisconsinense and
Peridiniopsis polonicium were most abundant in the summer. These differing patterns
56
may be attributable to a number of dynamic environmental variables or interactions of
those variables.
Many environmental variables contribute to the bottom-up and top-down control
of dinoflagellate populations in freshwater systems. Those that are likely to be important
in determining the temporal and spatial patterns in abundance and species composition of
the dinoflagellates in Boondoggle Lake include, but are not limited to, low nutrient
levels, an acidic pH, summer anoxia, warm temperatures, wind protection, and
interspecific competition.
The low phosphate levels in Boondoggle Lake may be a major contributor to the
relative success of dinoflagellates species. Low concentrations of orthophosphate,
between 1-10 ppb, are often found in freshwater systems where dinoflagellate blooms
occur (Pollingher 1987). The persistence of Peridinium at low phosphate levels is
thought to be due to its ability to take up and store phosphate in an internal pool of
polyphosphates during times of higher phosphate concentrations (Serruya and Berman
1975; Elgavish et. al. 1980). Because the detection limit for orthophosphate in this study
was 10 ppb, it is probable that orthophosphate was not detected simply because it was
below the detection limit.
The pH range of Boondoggle Lake (5.5-6.5) influences species diversity because
it excludes species of dinoflagellates that are not tolerant of acidic environments. Acid
tolerant species are not necessarily acidophilic and may remain at low population sizes
because of reduced growth rates in acidic environments. According to Pollingher (1987),
most freshwater dinoflagellates prefer alkaline environments. Since the pH in
Boondoggle Lake is always acidic, the six species identified in this study must tolerate or
57
prefer acidic environments. The effect of pH on growth rate has been investigated in four
of the six species of this study. Experiments with pure cultures showed P. inconspicuum
did not vary in growth rate across a wide range of pH (5.5- 8.5), but Peridiniopsis
polonicium had reduced growth rates under slightly acidic (6.5) and basic (8.5)
conditions. The same study found that P. volzii and P. limbatum had higher growth rates
under acidic conditions (Holt 1981). A water quality assessment for Echo Lake in New
York found P. deflandrei to be the most abundant species (40% of the phytoplankton),
with lake pH values being between 6.7 and 7.7 (CSLAP 2002). Although there are no
studies of the effect of pH on growth rate of P. deflandrei, it is clear from this study that
it can thrive in at least a slightly acidic environment.
Bottom water anoxia is likely to be one of the key factors controlling vertical
distribution of dinoflagellates in Boondoggle Lake. As mentioned earlier, dinoflagellates
are thought to be intolerant of low oxygen concentrations. If this is true for all species,
then dinoflagellates should be restricted to the epilimnion during the summer when
anoxic conditions are present below the oxygen chemocline. Indeed, the total
dinoflagellate density remained low at 2 m during the anoxic period, with the exception
of a large peak on September 13 (see Figure 5.1). On this date, anoxia was present at
2 m, whereas oxygen at 1.75 m was 4.25 mg/L. This high density value recorded at 2 m
under anoxic conditions is likely due to an error in sampling around the depth of the
oxygen chemocline. This pattern suggests a high density of dinoflagellates at the oxic-
anoxic boundary. If conditions are favorable for growth of dinoflagellates at 2 m before
the onset of anoxia, then development of anoxia in the bottom waters could be forcing an
58
upward vertical migration and subsequent concentration of dinoflagellates in the top 1 m
of the lake.
Temperature likely plays a general role in determining species abundance. Most
dinoflagellates show maximum growth during the summer (Carty 2003). This pattern
was seen for P. deflandrei, P. wisconsinense, and Peridiniopsis polonicium but not for P.
volzii and P. limbatum. P. volzii and P. limbatum may be inhibited by warm summer
temperatures, or other factors may be responsible for their absence in the summer.
Another potential advantage for dinoflagellates in Boondoggle Lake is that the
lake is protected from wind by hills to the west and south. Wind protection favors
dinoflagellates in two ways. First, phytoplankton that do not actively swim are lost more
rapidly from the water column through sedimentation in wind protected lakes, reducing
their level of competition with dinoflagellates (Pollingher 1988). Second, dinoflagellates
are likely to suffer less mortality from turbulence under wind protected conditions
(Pollingher and Zemel 1981).
Interspecific competition between dinoflagellate species may be important in
determining which species dominate the summer bloom. Physiological features may
confer advantages to certain species. For instance, species that are facultative
heterotrophs may be able to obtain carbon and nutrients to which obligate autotrophs
have no access. It is difficult to estimate how much effect interspecific competition may
have since few studies have investigated this topic with freshwater dinoflagellates.
More information on the physiology and ecology of the dinoflagellate species
from Boondoggle Lake is needed to understand which factors are most important in the
development of the large summer population of P. deflandrei and to understand why the
59
other species do not reach such high population densities. Priorities for future research
include more sensitive and comprehensive measurements of nitrogen and phosphorus and
measurements of dissolved organic carbon. Vertical profiles of light intensity are also
needed in order to determine a light extinction coefficient and estimate the depth of the
euphotic zone. A quantification of P. inconspicuum should be made in order to include
its seasonal abundance as part of the total armored dinoflagellates in Boondoggle Lake.
Because horizontal heterogeneity is often observed in freshwater dinoflagellate blooms
(Pollingher 1988), samples from more than one site are needed to describe the horizontal
spatial variation associated with these populations. Lastly, measurements of diel vertical
migration should be made.
Resources permitting, more extensive studies would be able to provide an even
more comprehensive data set on the ecology of Boondoggle Lake dinoflagellates. Using
sediment traps, measurements of the time of encystment and the amount of cysts formed
for each species could be made. Enumeration of cysts from sediment samples and an
attempt to induce excystment in a laboratory could also yield important data. All of these
measurements would be important in determining the role of cyst recruitment in
population dynamics. If these dinoflagellates could be brought into culture, estimates of
peridinin to chlorophyll a ratios within cells could be made, allowing an accurate estimate
of the percent of total algal biomass due to dinoflagellates using HPLC pigment analysis.
60
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65