Phytoplankton dynamics in a chain of subtropical blackwater lakes: the Upper St. Johns River, Florida, USA

Figures & data

Figure 1 Location of monthly phytoplankton and water quality sampling stations. BCL = Blue Cypress Lake; HBO = outlet of Lake Hell ′n Blazes; SGO = outlet of Sawgrass Lake; LWC = center of Lake Washington; LWO = outlet of Lake Winder; LPO = outlet of Lake Poinsett.

Table 1 Method of analysis of water quality samples. “SM” refers to Standard Methods for Analysis of Water and Wastewater (APHA 1998); “EPA” refers to Methods for the Chemical Analysis of Water and Wastes (USEPA 1983).

Analyte	Method	Instrument
Dissolved O2	SM 4500 G.	YSI 600XLB
Conductivity	SM 2510	YSI 600XLB
pH	SM 4500	YSI 600XLB
TKN	EPA 351.2	OI Analytical FS 3000
Chloride	EPA 300.0	Dionex DX-120
TP	EPA 365.4	OI Analytical FS 3000
NO x -N	EPA 353.2	OI Analytical FS 3000
NH4-N	EPA 350.1	OI Analytical FS 3000
PO4-P	EPA 365.1	OI Analytical FS 3000
DOC	EPA 415.1	Shimadzu TOC csh
Color	SM 2120 B.	Hellige Aqua Tester, Model 611
Metals	EPA 200.7	JY Optima ICP

Figure 2 Average monthly biovolume in lakes of the Upper St. Johns River. Lakes arranged in order from upstream (BCL = Blue Cypress Lake) to downstream (LPO = Lake Poinsett).

Table 2 Relative phytoplankton community composition in lakes of the Upper St. Johns River. Values represents an average of 30 months of biovolume data.

	%
Lake	Cyano.	Diatoms	Green	Dominant genera
Blue Cypress	1.9	54.2	3.1	Aulacoseira, Urosolenia
Hell ′n Blazes	7.6	39.5	10.8	Aulacoseira, Craticula
Sawgrass	11.6	56.8	4.6	Aulacoseira, Surirella
Washington	54.1	26.3	4.4	Anabaena, Aphanocapsa
Winder	42.8	36.7	6.2	Anabaena, Aphanocapsa
Poinsett	52.5	24.7	6.8	Planktolyngbya, Anabaena

Figure 3 Relationship between total community average monthly biovolume and community diversity. Left axis refers to the number of genera that comprises 90% of the community biovolume (bars). Line (right axis) depicts total algal biovolume.

Figure 4 Seasonal variation in biovolume in lakes of the Upper St. Johns River. Data represent average of all six lakes. Discharge data represent mean monthly values from USGS gauging station at US Highway 192, for period of record January 2001 through December 2004.

Table 3 Top 10 species of diatom, cyanobacteria, and green algae in the lakes of the Upper St. Johns River. Ranking based on total biovolume of all algal divisions.

Genus	Species	% of total algal biovolume
Diatoms
Aulacoseira	italica	8.4
Centric diatom	spp.	7.7
Plagiotropis	lepidoptera	3.6
Aulacoseira	ambigua/italica	3.6
Surirella	sp.	1.5
Craticula	sp.	1.4
Thalassiosira	bramaputrae	1.2
Aulacoseira	granulata v. angustissima	0.9
Nitzschia	sp.	0.5
Cyanobacteria
Anabaena	sp.	6.8
Planktolyngbya	limnetica	3.6
Anabaena	cf. oumiana	2.9
Aphanocapsa	sp.	2.7
Anabaena	circinalis	2.2
Aphanocapsa	holsatica	2.1
Oscillatoria	limosa	1.4
Anabaena	spiroides	1.2
Planktolyngbya	cf. microspira	1.1
Anabaena	flos-aquae	0.9
Green Algae
Scenedesmus	quadricauda	0.6
Spirogyra	sp.	0.5
Ankistrodesmus	falcatus	0.4
Pediastrum	duplex	0.4
Chlorophyte	sp.	0.3
flagellate
Pediastrum	simplex	0.3
Chlorophyte	sp.	0.2
unicell
Scenedesmus	protuberans	0.2
Chlamydomonas	sp.	0.4
Tetraselmis	cordiformis	0.2

Figure 5 Top five diatom genera in USJRB lakes. Bars represent the average monthly biovolume of 30 months of data, from March 2001 through November 2004. Note variable y-axis scaling.

Figure 6 Top five cyanobacteria genera in USJRB lakes. Bars represent the average monthly biovolume of 30 months of data, from March 2001 through November 2004. Note variable y-axis scaling.

Figure 7 Top five green algal genera in USJRB lakes. Bars represent the average monthly biovolume of 30 months of data, from March 2001 through November 2004. Note variable y-axis scaling.

Table 4 Average value of selected physical and chemical characteristics of Upper St. Johns River lakes. Summary statistics cover period of record from March 2001 through November 2005. Values in parentheses represent one standard deviation. Values with same superscript letter are not significantly different at P = 0.05.

	Surface Area ^1 ha	pH units	O2 mg/L	Chlorophyll-a mg/m^3	Color PCU	Conductivity μ S/cm
Lake
Blue Cypress	2653	7.35 (0.32)^ab	7.13 (1.58)^a	4.8 (5.9)^a	314 (142)^a	191 (32)^a
Hell ′n Blazes	154	7.12 (0.39)^b	4.81(2.71)^b	17.9 (12.8)^b	228 (112)^a	424 (128)^b
Sawgrass	195	7.28 (0.73)^ab	4.50 (2.86)^b	18.1 (17.1)^b	230 (103)^a	354 (114)^bc
Washington	1766	7.53 (0.52)^a	6.24 (2.42)^bc	13.9 (15.4)^b	226 (113)^a	434 (295)^bc
Winder	606	7.43 (0.60)^ab	5.47 (2.63)^bc	22.2 (18.6)^b	218 (106)^a	617 (425)^bc
Poinsett	1755	7.58 (0.52)^a	6.87 (1.89)^c	14.9 (22.4)^b	234 (127)^a	732 (513)^c

Table 5 Average value of selected water quality constituents for Upper St. Johns River lakes. Summary statistics cover period of record from March 2001 through November 2005. Values in parentheses represent one standard deviation. Values with same superscript letter are not significantly different at P = 0.05.

	PO4-P	NH4-N	NO3-N	TP	TKN	TSS	Chloride
Lake	mg/L
Blue Cypress	0.069 (0.023)^a	0.028 (0.019)^a	0.157 (0.095)^a	0.111 (0.032)^a	1.42 (0.20)^a	6.1 (4.21)^a	32 (6)^a
Hell ′n Blazes	0.050 (0.027)^ab	0.079 (0.089)^b	0.041 (0.044)^bc	0.110 (0.041)^a	2.06 (0.45)^b	11.2 (8.9)^ab	71 (27)^bcd
Sawgrass	0.036 (0.021)^b	0.064 (0.055)^b	0.024 (0.032)^bc	0.091 (0.040)^a	1.92 (0.34)^b	7.7 (4.6)^ab	59 (23)^b
Washington	0.038 (0.026)^b	0.066 (0.068)^b	0.070 (0.078)^ac	0.086 (0.048)^a	1.90 (0.39)^b	10.1 (11.9)^ab	71 (28)^c
Winder	0.045 (0.037)^b	0.069 (0.055)^b	0.037 (0.062)^bc	0.106 (0.063)^a	2.02 (0.52)^b	12.5 (9.2)^b	120 (92)^d
Poinsett	0.048 (0.059)^b	0.088 (0.103)^b	0.079 (0.105)^ac	0.099 (0.082)^a	2.00 (0.65)^b	12.6 (18.0)^ab	149 (120)^d

Table 6 Results of principal components analysis showing coefficients on each standardized water quality variable, as well as the percent of cumulative variance explained by the first three components.

	Eigenvectors
Variable	PC1	PC2	PC3
Alk	0.308	0.245	−0.009
Calcium	0.376	0.216	0.174
Chloride	0.346	0.173	0.227
Color	−0.324	0.083	0.021
Total P	−0.223	0.356	0.304
Conductivity	0.357	0.200	0.206
Diss. O2	0.157	−0.476	0.314
Iron	−0.242	0.097	0.469
NH4-N	−0.109	0.335	−0.204
NO x	−0.113	−0.325	0.396
pH	0.297	−0.283	0.150
PO4-P	−0.312	0.201	0.217
Secchi	0.174	−0.019	−0.397
TKN	0.198	0.338	0.196
Cum. % variance	0.405	0.564	0.698

Figure 8 Principal component analysis of Upper St. Johns River water quality data. Each point represents a single water quality sample. The ellipse in the lower left of the graph encircles samples collected primarily from Blue Cypress Lake.

Table 7 Pearson correlation coefficients (r) and significance level (p) for the relationship between cyanobacteria algal biovolume and selected water quality parameters for lakes in the Upper St. Johns River.

Parameter	r	P
Calcium	0.535	<0.000
Chlorophyll a	0.662	<0.000
Chloride	0.586	<0.000
Color	−0.286	<0.000
Water temperature	0.273	<0.000
Total kjeldahl N	0.554	<0.000
Conductivity	0.561	<0.000
pH	0.419	<0.000
Nitrate + Nitrite	−0.214	0.005
River stage	−0.202	0.007
Alkalinity	0.180	0.017
Iron	−0.136	0.073
Total phosphorus	0.104	0.169
Soluble P	0.073	0.338
Dissolved O2	0.073	0.340

Table 8 Results of step-wise linear regression of fourteen water quality parameters on log-transformed cyanobacterial biovolume. All model terms significant at p < 0.01.

Parameter	Units	Incremental r^2	Coefficient
Physical and Water Quality Data (Constant = −10.8)
Temperature	°C	0.54	0.315
TKN	mg/L	0.59	1.30
Stage	ft	0.62	4.13
Color	PCU	0.63	−0.0043
Water Quality Data Only (Constant = −0.76)
NO3	mg/L	0.28	−7.7
DO	mg/L	0.36	−0.54
EC	μ S/cm	0.44	0.002
Alkalinity	mg/L	0.46	−0.03
TKN	mg/L	0.48	0.68
pH	units	0.49	1.12
Secchi	m	0.51	−1.44