Survey of toxic algal (microcystin) distribution in Florida lakes

Figures & data

Table 1 Summary statistics for nutrients (μ g/L), chlorophyll (μ g/L), Secchi depth (m) and microcystin concentrations (μ g/L) for the annual average of 187 Florida lakes and 862 individual water samples collected Jan to Dec 2006.

	n	Mean	Min	Max
187 lakes annual average
Total phosphorus	187	42	2.7	283
Total nitrogen	187	1052	74	3450
Chlorophyll	187	25	0.42	172
Secchi depth	179	1.7	0.3	7.8
Microcystin concentration	187	0.4	ND*	12
862 individual samples
Total phosphorus	860	44	2	427
Total nitrogen	860	1043	33	5717
Chlorophyll	856	25	0.3	280
Secchi depth	788	1.6	0.2	9.8
Microcystin concentration	862	0.4	ND*	32

Figure 1 The 187 Florida lakes sampled for microcystin Jan to Dec 2006 and the Harris Chain of Lakes (Beauclaire, Dora [East and West], Eustis, Harris and Griffin) located in Lake County, FL, sampled for microcystin Sep 2006 to Aug 2007.

Figure 2 The mean percent difference of microcystin concentrations from annual means averaged across time periods for individual water samples categorized into trophic states and the individual water samples (hypereutrophic) from the Harris Chain of Lakes. The number of individual water samples for each time period is listed. Error bars represent the standard error of the mean for the mean percent differences of each time period.

Table 2 Percent by trophic state category (based on chlorophyll concentrations), in which microcystins were detected (≥ 0.1 μ g/L) for the 187 Florida lakes (annual average) and 862 individual water samples collected Jan to Dec 2006.

Trophic State	n lakes annual average	% detectable microcystin	n individual samples	% detectable microcystin
Oligotrophic	24	12%	102	18%
Mesotrophic	48	14%	221	17%
Eutrophic	80	36%	378	33%
Hypereutrophic	35	86%	161	76%
*Trophic states categorized by chlorophyll concentrations as indicated by Forsburg and Ryding (1980).

Figure 3 Individual samples (○) measured for microcystin concentration (N = 862) from 187 Florida lakes sampled Jan to Dec 2006. Total algal biomass values were calculated from chlorophyll concentrations using an equation specific to Florida (Canfield et al. 1985). The closed circles (•) represent the relationship between total algal biomass and percent algal contribution for cyanobacteria in Florida lakes as suggested by Duarte et al. (1992).

Table 3 Probability (%) that microcystin concentrations (μ g/L) will exceed the listed WHO microcystin guidance values as suggested by the chlorophyll concentration (μ g/L) categories, which were constructed to include at least 50 of the individual water samples (N = 856) collected from the 187 Florida lakes.

		Microcystin concentration (μ g/L) of 856 individual water samples
Chlorophyll (μ g/L)	n	< 1	1 ≤ × < 20	≥ 20
0–1.9	59	100%	0%	0%
2–2.9	75	100%	0%	0%
3–3.9	70	100%	0%	0%
4–4.9	61	100%	0%	0%
5–5.9	53	100%	0%	0%
6–7.9	86	99%	1%	0%
8–10.9	77	100%	0%	0%
11–13.9	54	94%	6%	0%
14–21.9	64	95%	5%	0%
22–31.9	56	91%	9%	0%
32–42.9	56	89%	11%	0%
43–69.9	63	83%	17%	0%
70–128	53	70%	30%	0%
130–280	29	45%	48%	7%

Table 4 Probability (%) that microcystin concentrations (μ g/L) will exceed the listed WHO microcystin guidance values as suggested by the Secchi depth (m) categories, which were constructed to include at least 50 of the individual water samples (N = 788) collected from the 187 Florida lakes.

		Microcystin concentration (μ g/L) of 788 individual water samples
Secchi depth (m)	n	< 1	1 ≤ × < 20	≥ 20
0.0–0.39	73	68%	29%	3%
0.40–0.53	55	76%	24%	0%
0.54–0.61	60	92%	8%	0%
0.62–0.76	59	90%	10%	0%
0.77–0.91	76	96%	4%	0%
0.92–1.13	55	93%	7%	0%
1.14–1.28	57	95%	5%	0%
1.29–1.52	53	98%	2%	0%
1.53–1.89	61	95%	5%	0%
1.90–2.39	55	100%	0%	0%
2.40–2.91	66	100%	0%	0%
2.92–3.81	60	100%	0%	0%
3.82–4.00	58	100%	0%	0%

Table 5 Summary statistics for nutrient (μ g/L), chlorophyll (μ g/L), Secchi depth (m) and microcystin concentrations (μ g/L) of 216 individual samples collected from Sep 2006 to Aug 2007 from six Harris Chain of Lakes located in Lake County, FL.

	n	Mean	Min	Max
Total phosphorus	213	57	29	130
Total nitrogen	213	3133	1530	5040
Chlorophyll	212	127	53	296
Secchi depth	216	0.3	0.2	0.7
Microcystin concentration	216	1.0	ND*	3.6

Figure 4 Mean monthly microcystin concentrations for six Harris Chain of Lakes located in Lake County, FL, sampled Sep 2006 to Aug 2007.

Forsburg , C. and Ryding , S. O. 1980 . Eutrophication parameters and trophic state indices in 30 Swedish waste-receiving lakes . Arch. Hydrobiol. , 89 : 189 – 207 .

 Google Scholar

Canfield , D. E. Jr. , Linda , S. B. and Hodgson , L. M. 1985 . Chlorophyll-biomass-nutrient relationships for natural assemblages of Florida phytoplankton . Water Resour. Bull. , 21 ( 3 ) : 381 – 391 .

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Duarte , C. M. , Agusti , S. and Canfield , D. E. Jr. 1992 . Patterns in phytoplankton community structure in Florida lakes . Limnol. Oceanogr. , 37 ( 1 ) : 155 – 161 .

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