Journal of Water Resource and Protection, 2013, 5, 732-742 Published Online July 2013 (
Changes in Diatom Biodiversity in Lake Sinclair,
Baldwin County, Georgia, USA
Marká E. Smith*, Kalina M. Manoylov
Department of Biological and Environmental Sciences, Georgia College and State University, Milledgeville, USA
Email: *
Received April 29, 2013; revised May 28, 2013; accepted June 22, 2013
Copyright © 2013 Marká E. Smith, Kalina M. Manoylov. This is an open access article distributed under the Creative Commons
Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is
properly cited.
The effects of increased water temperature on algal community composition were investigated in Lake Sinclair, Bald-
win County, Georgia, USA. The lake received waste cooling water from a coal burning power plant. Discharges of re-
cycled lake water were, on average, 15˚C ± 1.5˚C (and up to 23˚C) warmer than typical ambient temperatures. Seasonal
changes in algal composition were observed, and the warmer sample site had a greater diversity of diatom species year
round independent of changes in temperature. Thermal pollution created a high percent dissimilarity between diatoms at
the warmer site and the remainder of the lake. Species turnover observed in natural samples was not detected for the
warmer site. Anthropogenic thermal pollution was implicated as the factor inducing changes in the natural algal com-
munity composition, which may impact other trophic levels and ultimately the overall ecology of Lake Sinclair.
Keywords: Diatoms; Heated Water; Southern Lakes; Thermal Pollution
1. Introduction
Thermal pollution is the degradation of water quality by
any process that changes the ambient water temperature.
Persistent differences in ambient water temperature may
result in eutrophication, loss of ecosystem processes such
as biological productivity and lake metabolism, con-
taminant toxicity, and loss of aquatic biodiversity [1]. It
has been reported that cooling systems from coal burning
power plants have no harmful effects on a system as a
whole [2]. However, effects of thermal pollution in aqua-
tic systems are greatly influenced by industry, agriculture,
and urban habitats [1,3-9]. Effect of thermal pollution on
algae has not been addressed in Georgia, but in a sou-
thwestern lake thermal loading depressed primary pro-
duction of phytoplankton [10]. Lake Sinclair, in Central
Georgia, is a manmade lake owned by Georgia Power.
Water from the lake is used to cool the turbines of a coal
burning Power plant. About a billion gallons of water per
day is extracted from the lake, and when pumped back
into the lake it is intended to be within a few degrees of
the ambient temperature [11]. The effects of thermal
pollution have been documented previously [12], and it
was reported that approximately 3% of the lake was di-
rectly impacted by water that was too warm when it was
Cooling towers are supposed to decrease water tem-
perature to ambient temperatures before being released,
reducing the impact of thermal pollution on the sur-
rounding system [13]. In 2002, Georgia Power finished
installing a cooling tower to comply with Georgia Envi-
ronmental Protection Division’s (GA EPD) [14] regula-
tion to control effluent water temperature. The other
condition required for compliance is that at no time is the
temperature of the receiving waters to be increased by
more than 15˚C above intake temperature or the lake’s
natural temperature gradient. The installation was done
in response to a number of fish kills in the 1990’s in
Beaverdam Creek [15]. Past research on Lake Sinclair is
limited, with little to no research on potential thermal
pollution and its effects on primary producers. The State
of Georgia has continuously monitored temperature data
from DNR/EPD/Watershed Protection Branch since 2009.
Three sites that the State monitored on Lake Sinclair
provided additional temperature information in this study
for the baseline conditions within the lake.
Diatoms (Bacillariophyta) are often reported as the
dominant group in lake communities [16] and are known
to show definitive responses to different stressors and
environmental conditions [17-21]. Their rapid cell cycles
have been used to infer changes in composition due to
*Corresponding author.
opyright © 2013 SciRes. JWARP
anthropogenic influences from days to weeks [22,23].
Diatoms are able to recolonize bare surfaces as primary
colonizers in approximately 14 days [24]. They have also
been used extensively to directly infer climate variables,
such as temperature [25,26], but never as a model to un-
derstand thermal pollution within the same aquatic habi-
tat. Diatoms are particularly useful for assessing envi-
ronmental change because of their fast response rate and
potential presence in sedimentary records, which means
they can be used to compare past with present communi-
ties. Diatoms were used to detect shifts due to global
warming when there were changes of only a few degrees
centigrade [1], and the community composition shifted to
species that preferred longer growing seasons with less
ice cover [27-29]. A shift from primarily benthic diatoms
to planktonic species has also been suggested as a sign
that warming is occurring [30-37]. Visible changes in
community dominance of diatoms followed by satellite
imagery showed the effects of thermal pollution on shal-
low estuaries [38], and as little as 1˚C temperature in-
crease changed the dominant species composition in the
local area.
Species richness, diversity, and evenness are routinely
used to assess community change and. In the case of cli-
mate, warmer temperatures have been found to favor
higher biological production [39]. High species richness
is a measure of high biotic integrity, because of the vari-
ety of habitats present and the ability of taxa to adapt to
the available niches [40]. Much research on algae has
addressed the relationship between species richness and
nutrient concentrations [41,42]. High nutrient concentra-
tions can lead to toxic blooms [43]. However, many
habitats may be naturally stressed by low nutrients, low
light, low temperature or other factors [18]. A slight in-
crease in nutrient enrichment has been shown to trigger
an increase in algal species richness in headwater and
naturally unproductive, nutrient poor streams [44]. Tem-
perature changes may have a similar effect [45].
However, information from stressor specific monitor-
ing is generally lacking. Little is known about the eco-
logical impacts of thermal pollution on primary produc-
ers within the same lake. In an attempt to determine the
nature and magnitude of environmental changes in a lake
impacted by anthropogenic temperature increase, two
sites on Lake Sinclair were systematically monitored and
diatom species composition was analyzed to assess re-
sponse to temperature differences. It can be expected that
some algal species differ at the two sites because they
have different tolerances to temperature. The goals of
this study were to: 1) understand the biological impacts
of thermal pollution in Lake Sinclair; 2) evaluate the
changes in primary producer community structure and
function due to changes in temperature; and 3) assess the
potential of change in diatom community structure as an
indicator of thermal pollution.
2. Materials and Methods
2.1. Study Area: Lake Sinclair, from the Oconee
River Watershed
Lake Sinclair is located in central Georgia on the Oconee
River watershed (33˚1049.06N, 83˚1728.70W). It stret-
ches through three counties including Baldwin, Hancock,
and Putnam. The Oconee River is the main source of
water for this reservoir and supplies 70% of the lake’s
water. The lake is also fed by waters from the Apalachee
River and several small creeks in the area [46]. The re-
gion is characterized by a warm and humid, temperate
climate. The average annual temperature is about 15.6˚C.
Runoff is not generally significant.
The Oconee River basin contains parts of the Pied-
mont and Coastal Plain physiographic provinces, which
extend throughout the southeastern United States. Lake
Sinclair sits on the Piedmont region. Predominant soil
types are sandy loam clay to fine sandy loam [13].
Lake Sinclair is a manmade lake created in 1953. It is
the second largest reservoir in Georgia (surface area 62
km²) and has a maximum depth of 27 m. Lake Sinclair
and Lake Oconee are considered oligotrophic lakes, with
deep nutrient poor lake basins with sandy or rocky bot-
toms, and scarce bottom vegetation. Georgia Power, a
Southern Company, owns the lake and uses it as a reser-
voir to cool the turbines in their coal burning plant. In
addition, the lake area is used for residential housing and
recreation. In the counties surrounding the lake, there is a
population of about 150,000. The counties that surround
Lake Sinclair remain heavily forested by oak/pine forests
with little agriculture and industry [13]. The agriculture
and housing developments on water bodies above Lake
Sinclair have little to no influence on the streams and
lakes themselves [47].
2.2. Sampling Site Locations
Prior to this study, non-significant differences in diatom
community composition from Lake Sinclair were re-
ported in 22 sites [47,48]. For the current study, two sites
on Lake Sinclair were chosen for comparison of the
temperature effects. One in the immediate “warmer” area
of the power plant (where discharge from the cooling
tower occurs), and the other was approximately 1.7 km to
the south representing ambient temperatures, “the cooler
or cold site”. The cold and warm locations were sampled
for seven months. There were a total of 15 samples taken
from each sample site. Sampling methods followed
Standard protocols [49,50]. Once collected, the samples
were transported to the laboratory in a cooler with ice
and immediately preserved. Algal samples were pre-
served with 3% formaldehyde for later processing and
Copyright © 2013 SciRes. JWARP
identification [50].
Algal samples were collected approximately every 14
days from August 2008 to February 2009, along with
triplicate measures of water temperature, pH, and con-
ductivity with YSI 556 MPS instrument. Turbidity was
measured using a LaMotte® Portable Turbidity meter.
Turbidity was measured as having sediment or foreign
particles stirred up or suspended, muddy. Based on the
GA EPD requirement for small differences in natural
habitats due to human activities, temperature differences
between the two sites were categorized as 1 = small dif-
ferences from 1˚C to 10˚C, 2 = medium differences from
11˚C to 20˚C, and 3 = high differences more than 20˚C.
After classification, 4 sampling events fell into the first
category, 5 fell into the second category, and 6 fell into
the third category for a total of 15 sampling events. A
Secchi disc (Carolina biological Inc.) was used to evalu-
ate the depth of the photic zone. Water for nutrients
analyses was collected in 125 ml acid washed bottles and
sent to the University of Georgia Marine Extension Ser-
vice and University of Georgia commercial chemical ana-
lyses lab in Athens, Georgia. Water samples were ana-
lyzed for nutrients including Ammonium, Nitrate/Nitrite,
Total Nitrogen, and total Phosphorus. Three further sam-
ples were taken for nutrient analysis and compared to
Georgia’s DNR data, but there were no significant dif-
ferences in nutrient concentrations.
Lab analysis of algal diatom assemblage composition
was performed using cleaned (digested) samples pre-
served on permanent slides [50]. The samples were
cleaned of organic matter in 50% nitric acid for 2 hours.
Then less than one gram of potassium dichromate was
added to them as a catalyzer, heated for approximately 5
minutes and left to cool for 30 minutes. Permanent dia-
tom slides were prepared by acid cleaning, to increase
the clarity of observing diatoms [51], and then mounted
in Naphrax resin (RI 1.74, Northern Biological Supplies
L., Ipswich, UK). Taxa that appeared as auxospores or
single broken valves without the central area were not
included in the analyses.
At least 300 valves were counted from each sample
using the 1000x objective lens on an Aus JenaLumar
scope (AUSJena Germany). Diatoms were identified to
the lowest taxonomic unit using standard identification
keys and following standard procedures for diatom iden-
tifications [51-56].
2.3. Diatom Indices
Presence or absence and species numbers were recorded
at the cold site and the warm site. Species richness de-
scribes the number of species in a habitat. Species even-
ness [57] represents the relative abundance of species in
a community (if one taxon dominates the community and
there are many rare taxa, evenness will be close to 0).
Species diversity is a measure of diversity that increases
with either species richness or species evenness. The
Shannon diversity index considers species richness and
proportion of species in a site [58]. Lastly, 2 other meas-
ures were utilized to compare the sites. Similarity rich-
ness Index (S = 2C/A + B) and % Dissimilarity index
(%D = 100 minus Σ min relative abundance of “C”),
where C is the number of common species between the
two sites, A is the number of species in one site, B is the
number of species in the other site and “C” is relative
abundance of common taxon that appeared in both sites;
the smaller of the 2 relative abundances is summed for
the index [59]. Similarity varies from 0 to 1, high Simi-
larity is expected at 0.7 and above. Dissimilarity values
vary from 0 to 100% with values close to 0 indicating
identical communities and more than 50% indicating
very different diatom communities [60].
2.4. Statistical Analyses
To test if the number of rare taxa were significantly dif-
ferent between natural and high temperature impacted
sites, sites were compared with t tests as α = 0.05 and
significance was considered. If the assumptions for t test
were not met (e.g., normality, equal variance) and if
transformation did not help, the Mann Whitney non pa-
rametric test was used. Descriptive statistics, Pearson
correlations, and regression analyses were conducted to
analyze environmental variability and relationships be-
tween variables. Linear regression predicted patterns of
community indices in the warm and cold environments.
Statistical analyses were performed with SYSTAT® 13
3. Results
3.1. Physical Parameters
Temperatures at the cold site ranged from 10˚C to 31.5˚C
(mean 20.6˚C) and at the warm site from 29˚C to 35˚C
(mean 32.5˚C). The seasonal temperatures at the cold site
were normal for the lake but the warm site, which re-
ceived the cooling water discharge, showed little varia-
tion throughout the study. Temperature differences be-
tween the two sites diverged the most during the winter
season, while summer months temperature values over-
Dissolved oxygen concentrations at both sites were
similar, with 4.2 mg/L at the warm site and 4.7 mg/L at
the cold site, with the highest levels in winter, and de-
clining in the summer months. There was no statistical
difference between the dissolved oxygen at each site over
each sampling event. Average pH within the study area
was 7.04 ± 0.22 with values ranging from 6.82 to 7.26.
Secchi depth averaged 0.85 ± 0.50 m for the study area.
Conductivity averaged 66 ± 6.24 µS/cm for the study
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area. Turbidity in the study area averaged 14.32 NTU.
3.2. Nutrient Analyses
Water samples for nutrient analysis were taken three
times during this research, at the beginning the middle
and the end. The average concentrations of ammonia was
0.23 ± 0.04 mg/L, of nitrate was 0.17 ± 0.01 mg/L, and
total nitrogen 0.20 ± 0.18 mg/L. There was no statistical
difference between the nitrogen, ammonium, and total
phosphorus at each site over each sampling event.
3.3. Diatom Enumeration
There were a total of 131 diatom species observed from
the two sites at Lake Sinclair. Only 10 were considered
common species with relative abundance of >25% (Ta-
bles 1 and 2). Rare species made up approximately 90%
of the species documented during the study. Different
rare species were observed at both sites. Planktonic and
benthic diatoms were observed throughout the study.
Variation among total species richness remained low for
the duration of the study. The highest species richness in
the cold site occurred during the summer months with a
total of 37 species observed, which corresponded to the
highest Shannon diversity value. The warm sites highest
species richness occurred during the summer as well with
39 different species observed. This number correlated
with the highest Shannon diversity value for the warm
Table 1. Species that appeared in 25% or more relative abundanc e in cold habitat in Lake Sinclair, GA.
Date Diatom Species % RA
2008/10/27 Achnanthidium minutissimum (Kützing) Czarnecki 0.310
2008/11/1 Achnanthidium minutissimum (Kützing) Czarnecki 0.307
2008/12/5 Aulacoseira ambigua (Grunow in Van Heurck) Simonsen 0.310
2008/12/5 Discostella stelligera (Cleve et Grunow in Cleve) Houk et Klee 0.273
2009/1/16 Achnanthidium minutissimum (Kützing) Czarnecki 0.578
2009/1/16 Aulacoseira granulata (Ehrenberg) Simonsen 0.278
2009/1/25 Achnanthidium minutissimum (Kützing) Czarnecki 0.430
2009/2/11 Melosira varians Agardh 0.331
Table 2. Species that appeared in 25% or more relative abundanc e in warm habitat in Lake Sinclair, GA.
Date Diatom Species % RA
2008/9/3 Fragilaria capucina Desmazières var. mesolepta (Rabenhorst) Rabenhorst 0.276
2008/10/3 Achnanthidium catenatum (Bily et Marvan) Lange-Bertalot 0.313
2008/10/3 Achnanthidium minutissimum (Kützing) Czarnecki 0.280
2008/10/10 Achnanthidium catenatum (Bily et Marvan) Lange-Bertalot 0.247
2008/10/10 Achnanthidium minutissimum (Kützing) Czarnecki 0.440
2008/10/17 Achnanthidium minutissimum (Kützing) Czarnecki 0.273
2008/11/1 Encyonema silesiacum (Bleisch in Rabenhorst) Mann in Round 0.253
2008/11/7 Nitzschia filiformis var. conferta (Richter) Lange-Bertalot in Lange-Bertalot and Krammer 0.248
2008/11/17 Aulacoseira ambigua (Grunow in Van Heurck) Simonsen 0.277
2008/12/5 Aulacoseira granulata (Ehrenberg) Simonsen 0.333
2009/1/16 Aulacoseira granulata (Ehrenberg) Simonsen 0.291
2009/1/16 Thalassiosira pseudonana Hasle et Heimdal 0.258
2009/1/25 Achnanthidium minutissimum (Kützing) Czarnecki 0.333
2009/2/11 Achnanthidium catenatum (Bily et Marvan) Lange-Bertalot 0.424
2009/2/11 Achnanthidium minutissimum (Kützing) Czarnecki 0.435
water site as well.
There were 100 species recorded at the cold site. The
average number of species was 23 ± 1.90, ranging from
13 to 37 species. The highest species richness and even-
ness observed in the cold samples occurred during
warmer calendar months, when not a single taxon ap-
peared with more than 25% relative abundance (Table
There were a total of 103 diatom species documented
at the warm site. The average number of species was 23
± 1.87, ranging from13 to 39 species.
The cold water community was dominated by Ach-
nanthidium minutissimum (Kützing) Czarnecki (Table 1),
with secondary abundances of other pennate genera in-
cluding Nitzschia, Aulocoseria, Melosira, Synedra, and
Cymbella. For the warm site, the subdominant genera
like Aulacoseira and Cymbella were at much greater
abundances than in cold water. Cocconeis pediculus
Ehrenberg, Martyana martyi (Héribaud) Round, and Ca-
loneis schumanniana (Grunow in Van Heurck) Cleve,
were found only at the warm site (Table 2). Adlafia
minuscula (Grunow) Lange Bertalot, Amphipleura pellu-
cida (Kützing) Kützing, Diadesmis contenta (Grunow ex
Van Heurck) Mann in Round, Crawford and Mann, Fal-
lacia tenera (Hustedt in Schmidt) Mann in Round, Craw-
ford and Mann, Stephanodiscus minutulus (Kützing)
Cleve et Möller, and Tabularia fasciculata (Agardh)
Williams et Round were only present in the cold site.
Warm water community composition remained consis-
tent with the cold site throughout the year. However, as
the study progressed over time, the dominant species
shifted as the temperature changed in the cold sites more
than in the warm sites.
The Shannon diversity values for the cold site ranged
from 1.26 to 3.02. The warm sites values were compara-
ble, ranging from 1.73 to 3.10. When temperature dif-
ferences were small between the two sites, there were no
significant differences in values of the average Shannon
diversity. With a change in the seasons, the Shannon di-
versity values at both warm and cold site’ varied signifi-
cantly, showing an increase, on average, in the cold site
and a decrease in the average warm sites value. During
the winter months at the cold sites, the Shannon diversity
value decreased further while the warmer site stayed at
about the same. Evenness for the warm site ranged from
0.68 in October to 0.85 in August. The cold site had a
low evenness of 0.45 in February and a high evenness of
0.87 in November.
Similarity calculated with presence of common taxa at
both sites was very low and reached close to 50% only in
September (Table 3). Similarity based on species rich-
ness related common species between the two sites with
the total number of species in both areas. Dissimilarity
measured with minimum relative abundance of a com-
mon taxon for the two locations was very high for all
pairs (Table 3), dissimilarity decreased below 50% only
during one warmer calendar month. Average richness
similarity during winter months similarly was 0.08 to
0.43, dissimilarity based on species identity and relative
abundance was high throughout the sampling season.
Temperature explained one third to 50 % of the varia-
tion only for the cold or natural habitats (Table 4). The
Shannon diversity within the cold sites increased signifi-
cantly with temperature changes (Linear regression, y =
0.007x + 2.143, R² = 0.54, p = 0.002). The Species rich-
ness for the cold site increased with increase in tempera-
ture (Linear regression, y = 0.77x + 6.838, R² = 0.37, p =
0016). The Evenness for the cold site significantly in-
creased with temperature too (Linear regression, y =
0.013x + 0.511, R² = 0.52, p = 0.002). No significant
changes between the communities attributed and tem-
perature were documented for the warm site.
3.4. Representative Diatom Species Evaluations
(from the Taxonomic Literature)
Cocconeis pediculus Ehrenberg, is described as having a
valve that is strongly arched, broadly ellipitical. Interca-
lary band occasionally seen. Raphe valve with narrow,
linear axial area terminating in a small semicircular clear
space near the valve extremities. Centrals are small, cir-
Table 3. Species richness similarity and % abundance dis-
similarity of diatom community composition in warm and
cold sites within Lake Sinclair system for each sampling
Date Species Similarity Abundance % Dissimilarity
2008/8/27 0.1967 67
2008/9/3 0.2040 65
2008/9/12 0.4535 49
2008/9/26 0.5160 63
2008/10/3 0.4895 59
2008/10/10 0.3179 76
2008/10/17 0.3806 55
2008/10/27 0.4829 68
2008/11/1 0.1733 74
2008/11/7 0.1113 73
2008/11/17 0.1942 63
2008/12/5 0.2767 58
2009/1/16 0.3244 72
2009/1/25 0.4394 74
2009/2/11 0.0870 62
Copyright © 2013 SciRes. JWARP
Table 4. Mean, Standard Deviation, Regression equations, R², and p-values for cold and warm sites within Lake Sinclair.
Group Variable N Mean Std. Dev. Regression equation R² p-value
Shannon 15 2.43 0.506 y = 2.143 + 0.007x 0.54 0.002
Species Richness 15 23.133 7.347 y = 6.838 + 0.776x 0.37 0.016
Eveness 15 0.777 0.101 y = 0.511 + 0.013x 0.52 0.002
Shannon 15 2.346 0.433 y = 1.076 + 0.064x 0.01 ns
Species Richness 15 22.667 7.355 y = 21.1 + 0.0056x 0.002 ns
Eveness 15 0.76 0.09 y = 0.699 + 0.002x 0.02 ns
cular to somewhat irregular. Raphe filiform, proximal
ends close, extending into the central area; distal ends
straight, terminating at the small semicircular space near
the valve extremities. Striae curved-radiate, finely but
distinctly punctuate. Striae not extending completely to
the valve margin, but interrupted by a narrow, clear mar-
ginal area which is continuous around the valve much as
rim. Pseudoraphe valve with very narrow, linear pseu-
doraphe. Central area lacking. Striae also curved radiate,
faintly etched as a shallow trough, with distantly placed
conspicuous puncta. Puncta arranged in longitudinally
undulating rows. Straie, about 20 in 10 µ along the axial
area, 16 - 17 in 10 µ near the margins (RV); 18 in 10 µ
along the axial area, 15 - 16 in 10 µ near the margins
(PRV). Length, 11 µ - 30 µ. Breadth, 6 µ - 20 µ. The
range of this diatom has been reported in the South East-
ern United States. This species is a widespread species;
epiphytic on many aquatic plants and other objects, but
not often found in large numbers. Considered by some as
resistant to moderate amounts of organic pollution; alka-
liphil, and salt “indifferent”. The measured specimens
from our samples fell within the range of the given de-
Achnanthidium minutissimum (Kützing) Czarnecki
(Figure 1(7)) is described as having a valve linearel-
lipitical with obtusely rounded subrostrate to capitate
ends. Raphe valve with narrow, linear axial area and
narrow, somewhat irregularly shaped, central area occu-
pying up to about one-half the total width of the valve in
the middle portion. Raphe filiform; proximal raphe ends
close, distal ends curving subtlety in the same direction.
Striae slightly to moderately radiate, becoming more
numerous towards the ends. One or two shorter striae on
either side of the central area sometimes spaced slightly
farther apart than the reaming straie. Pseudoraphe valve
with narrow, linear axial area, slightly broadened in the
middle portion of the valve or with an occasional short-
ened stria at the center, but with no distinct central area
as such. Striae character and direction as on the raphe
valve. Striae, 30 - 32 in 10 µ at the center, becoming 36 -
38 in 10 µ near the ends (both valves). Length, 5 µ - 40 µ.
Breadth, 2 µ - 4 µ. This species has been reported in the
South Eastern United States. This species is described as
a very widespread taxon to be found throughout the
country, Eurytropic, Euryők. Found at very wide range of
pH about 6.5 - 9.0. Oligohalobe, probably “indifferent”.
The measurements in our study were in the range of the
given description.
Fragilaria capucina Desmazières var. mesolepta (Ra-
benhorst) Rabenhorst (Figure 2(2)) is described as hav-
ing a valve linear to linear-lanceolate, constricted at the
rectangularly shaped central area. Apices somewhat at-
tenuated, rostrate. Pseudoraphe very narrow. Central area
somewhat variable, may be longer than broad or broader
than long. Striae parallel, 15 - 18 in 10 µ. Length, 30 µ -
35 µ. Breadth in narrowest portion of the middle of the
valve, 2 µ - 4 µ. This taxon is distinguished from other
verities of this species by the constriction in the middle
portion of the valve. This species has been reported in the
South Eastern United States, and occurs in fresh water,
slightly alkaline; sometimes found in slightly brakish
(5) (6)
(7) (8) (9)
Figure 1. Warm water pennate araphid, monoraphid and
biraphid diatom taxa, (1 - 2) Fragilaria bidens Heiberg, (3)
Fragilaria sp., (4) Staurosirella sp. (5) Gomphonema sp., 6.
Gomphonema gracile Ehrenberg, (7) Achnanthidium minu-
tissimum (Kützing) Czarnecki, (8) Planothidium sp. (9) En-
cyonopsis microcephala (Grunow) Krammer. Scale bar is 10
Copyright © 2013 SciRes. JWARP
water. The specimens in our samples were not the same
size as the description given.
Encyonema silesiacum (Bleisch in Rabenhorst) Mann
in Round, Crawford and Mann (Figure 3(7)) is described
as having valves that are strongly dorsi-ventral with
rounded, undifferentiated apices. The dorsal margin is
strongly convex; the ventral margin is more or less
straight. The straie are parallel to slightly radiate. Axial
area is narrow linear, with slightly expanded central area.
Raphe is filiform and more or less straight. Proximal
raphe fissures are small pores; distal raphe fissures are
strongly deflected towards the ventral surface and ex-
tended along the valve margin. The isolated pore (stigma)
at the end of the central straie may or may not be dis-
cerned with LM. Areolae open externally as slits. Encyo-
nema silesiacum has fewer areolae/10 µm. Length 7 µm -
23 µm (Encyonema silesiacum usually larger). Width is 4
µm - 7 µm with a straie density of 15 - 18/10 µm. This
species was restricted to more eutrophic locali- ties with
higher pH and was never dominant in Lake Sin- clair
samples. The sizes of our specimens of this species were
not the same as the description given.
Aulacoseira ambigua (Grunow in Van Heurck) Si-
monsen (Figure 4(2)) is described as having cells that
are cylindrical with a mantle height to valve diameter
often between 1.5 and 3. The valve face is usually unor-
namented. Straie on the mantle composed of relatively
(5) (6)
Figure 2. Cold water Pennate araphid diatom taxa, (1)
Synedra ulna cf. Var ramesi, (2) Fragilaria capucina Desma-
zières var. mesolepta (Rabenhorst) Rabenhorst, (3) Tabu-
laria fasciculata (Agardh) Williams et Round, (4) Fragilaria
bidens Heiberg, (5) Pseudostaurosira brevistriata (Grunow in
Van Heurck) Williams et Round, (6) Martyana martyi (Héri-
baud) Round. Scale bar is 10 µm.
Figure 3. Cold water Pennate biraphid diatom taxa, (1) Bra-
chysira vitrea (Grunow) Ross in Hartley, (2) Diadesmis con-
tenta (Grunow ex Van Heurck) Mann in Round, Crawford
and Mann, (3) Encyonema minutum (Hilse in Rabenhorst)
Mann in Round, Crawford and Mann, (4) Encyonema sile-
siacum (Bleisch in Rabenhorst) Mann in Round, (5) Navi-
cula notha Wallace, (6) Gomphonema gracile Ehrenberg, (7)
Nitzschia filiformis var. conferta (Richter) Lange-Bertalot in
Lange-Bertalot and Krammer, (8) Fallacia tenera (Hustedt
in Schmidt et al.) Mann in Round, Crawford and Mann, (9)
Geissleria decussis (Østrup) Lange-Bertalot et Metzeltin.
Scale bar is 10 µm.
(5) (6) (8)
spines are short, and triangular, fork or heart-shaped.
Figure 4. Warm water Centric diatom taxa, (1) Aulacoseira
alpigena (Grunow in Van Heurck) Krammer, (2) Aulaco-
seira ambigua (Grunow in Van Heurck, (3 - 7) Aulacoseira
granulata (Ehrenberg) Simonsen, (8) Melos ira var ia ns Agardh;
scale bar 10 µm.
large, circular areolae that spiral to the right. Since each
mantle costae terminates with a spine on the valve face,
the density of spines equals the density of straie. Linking
Copyright © 2013 SciRes. JWARP
Although rare, separating spines are longer, pointed, and
also terminate the ends of each mantle costae. Cells have
a well-defined collum, the height of which is quite stable,
and a thick hollow Ringleiste that forms a characteristic
indentation when cells are viewed at mid-focus. The
height is 5 µm - 13 µm with a diameter of 4 µm - 17 µm.
This taxon is reported to be observed in slightly acidic to
slightly alkaline, and mesotrophic conditions. This is a
planktonic species that dominated in 6% of our commu-
nities. The specimens observed fell within the range of
the given description.
4. Discussion
d evidence for a shift from benthic to
ance of diatom species was expected to be
oal of assessing and managing aquatic
s excellent indi-
rst taxonomic evaluation of diatoms from
5. Acknowledgements
gia’s Environmental Protec-
[1] S. Kaushal, G. Pace, M. Sides, D.
ct of Strip-Cutting on
There was limite
planktonic diatoms as Lake Sinclair is very turbid with a
shallow photic zone as compared to arctic lakes where
most of the temperature relationships have been reported
[27-29]. During the warmer months of the study when
there was less than 10˚C temperature difference, diver-
sity values and richness were close in value. When the
seasons changed, there was a statistically significant dif-
ference between the sites that triggered on average 65%
dissimilarity. Within the median increase in temperature
differences (still less than 20˚C), cold sites were more
diverse. Diatom species composition, richness, and abun-
dance of naturally occurring species in Lake Sinclair
were significantly changed in parts of the lake with con-
stant high temperature. The expected decrease in native
taxa richness, because these taxa are less competitive in
higher temperature, was strongly suggested and observed.
Competitive exclusion for other limiting resources, in-
creased predation, or alteration of other abiotic factors
through indirect effects of temperature (e.g., dissolved
oxygen concentration, microbial interaction, or habitat
structure) may all be influencing diatom community cha-
The abund
ore sensitive to environmental changes than presence/
absence of taxa, because taxa were expected to change
their reproductive rate before being totally lost from a
habitat. Taxonomic evaluation of diatoms from natural
conditions in either low nutrients [62] or as evaluated in
this study, low temperature, present a valuable resource
for evaluation of changes due to human activities. Ideally,
reference conditions are developed according to the cen-
tral tendency and variability of natural or minimally dis-
turbed systems.
The ultimate g
osystems is to restore these ecosystems to natural con-
ditions, which will not be possible for Lake Sinclair. The
suite of community assessment presented here (such as
native conditions, diatom richness, relative abundance,
and species characteristics) should be monitored along
the temperature gradients in the future.
Diatoms have long been regarded a
tors of environmental change in aquatic systems, re-
sponding with quantifiable trends over relatively short
time periods. The warmer sample site was anticipated to
promote a greater diversity of species. As our results de-
monstrated, constant high temperature supported higher
biodiversity and prevented natural competitive processes
to take place as in the rest of the lake. Winter differences
in temperature were above regulation (GA EPD), and
significantly changed the community structure of the
primary producers. Anthropogenic thermal pollution is
implicated here as a factor inducing changes in the natu-
ral diatom community composition, which may impact
other trophic levels and ultimately the overall ecology of
Lake Sinclair.
This is the fi
ke Sinclair, and the observed (diatom dominated pri-
mary producers community) was due to changes in tem-
perature. The highest similarity values occurred when
temperature corresponded to high summer air tempera-
ture. Warmer water supported more algal species and
higher algal density. Inversely it was observed that as the
temperature dropped, similarity decreased and varied
with season. The temperature in the lake is affected by
recycled water that is released by the power plant daily.
Diatoms are an effective source for determining tem-
perature changes over a relatively short period of time
and good indicators of impairment.
We would like to thank Geor
tion Division and Georgia’s Department of Natural Re-
sources for the additional data.
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