To measure chlorophyll or phytoplankton biovolume: an aquatic conundrum with implications for the management of lakes

Figures & data

Table 1. Frequency distributions of trophic state parameters and temperature measured in individual water samples collected from Denmark (N = 10,658), Florida (N = 318), and during the U.S. Environmental Protection Agency’s (USEPA) National Lake Assessment (NLA) surveys (N = 2187). Numbers in parentheses are values from a randomized database where 200 samples each were taken from Denmark, Florida, and the NLA.

Variable	Minimum	25% Quantile	Mean	Median	75% Quantile	Maximum
Denmark
Chlorophyll (µg/L)	0.2 (0.9)	9 (7)	59 (63)	27 (28)	72 (83)	1100 (650)
Total P (µg/L)	2 (7)	50 (56)	167 (165)	96 (100)	200 (200)	2990 (2300)
Total N (µg/L)	33 (340)	960 (940)	2268 (760)	1600 (570)	2821 (930)	22,000 (6100)
Secchi (m)	0.1 (0.2)	0.7 (0.6)	1.7 (1.6)	1.3 (1.2)	2.2 (2.3)	11 (6.5)
Florida
Chlorophyll (µg/L)	0.3 (0.3)	3 (3)	18 (17)	5 (5)	17 (17)	311 (311)
Total P (µg/L)	1 (1)	11 (11)	50 (49)	21 (21)	43 (43)	1090 (1090)
Total N (µg/L)	65 (65)	370 (380)	780 (760)	560 (570)	950 (930)	6100 (6100)
Secchi (m)	0.1 (0.1)	0.6 (0.6)	1.8 (1.7)	1.2 (1.2)	2.4 (2.2)	9 (9)
USEPA NLA
Chlorophyll (µg/L)	<1 (<1)	3 (3)	28 (31)	8 (9)	26 (33)	940 (274)
Total P (µg/L)	1 (1)	14 (14)	115 (142)	35 (37)	95 (120)	4680 (3600)
Total N (µg/L)	5 (33)	320 (320)	1200 (1300)	610 (680)	1230 (1430)	54,000 (17000)
Secchi (m)	<0.1 (<0.1)	0.6 (0.6)	2.1 (2.1)	1.4 (1.2)	2.8 (2.6)	37 (28)

Table 2. Frequency distributions of phytoplankton groups measured concurrently with chemical and physical limnological state parameters in individual water samples collected from Denmark (N = 10,658), Florida (N = 318) and during the U.S. Environmental Protection Agency’s National Lake Assessment survey (N = 2,187). Numbers in parentheses are values from a randomized database where 200 samples each were taken from Denmark, Florida, and the NLA.

Total Biovolume (mm^3/L)
Phytoplankton Groups	Minimum	25% Quantile	Mean	Median	75% Quantile	Maximum
Denmark
Total	0.0 (<0.1)	1.1 (1.1)	10 (10)	4 (4)	11 (11)	1100 (110)
Cyanophyta	0.0 (0.0)	0.0 (0.0)	4 (4)	0.0 (0.1)	2 (3)	480 (110)
Chlorophyta	0.0 (0.0)	0.0 (<0.1)	2 (2)	0.1 (0.1)	0.9 (1)	1000 (51)
Diatom	0.0 (0.0)	0.0 (0.0)	2.0 (1.7)	0.1 (0.1)	1.2 (1.1)	177 (51)
Cryptophyta	0.0 (<0.1)	0.1 (0.1)	0.5 (0.7)	0.2 (0.2)	0.5 (0.7)	28 (11)
Dinoflagellate	0.0 (0.0)	0.0 (0.0)	0.9 (0.5)	0.0 (0.0)	0.1 (0.1)	234 (25)
Euglenoid	0.0 (0.0)	0.0 (0.0)	0.0 (<0.1)	0.0 (0.0)	0.0 (0.0)	31 (3)
Chrysophyta	0.0 (0.0)	0.0 (0.0)	0.0 (0.1)	0.0 (0.0)	0.0 (0.0)	5 (0.4)
Xanthophyta	0.0 (0.0)	0.0 (0.0)	0.0 (0.0)	0.0 (0.0)	0.0 (0.0)	4 (0.0)
Florida
Total	0.0 (0.1)	1 (1)	40 (45)	2 (3)	13 (14)	2900 (2900)
Cyanophyta	0.0 (0.0)	0.0 (0.0)	35 (40)	0.2 (0.3)	5 (6)	2900 (2900)
Chlorophyta	0.0 (0.0)	0.1 (0.1)	2 (2)	0.3 (0.3)	1.3 (1.4)	130 (35)
Diatom	0.0 (0.0)	0.0 (<0.1)	1.7 (1.7)	0.3 (0.3)	1.4 (1.6)	39 (39)
Cryptophyta	0.0 (<0.1)	0.0 (<0.1)	0.2 (0.2)	0.1 (0.1)	0.2 (0.2)	15 (3)
Dinoflagellate	0.0 (0.0)	0.0 (0.0)	0.3 (0.3)	<0.1 (<0.1)	0.2 (0.2)	11 (11)
Euglenoid	0.0 (0.0)	0.0 (0.0)	0.0 (<0.1)	0.0 (0.0)	0.0 (0.0)	3 (0.3)
Chrysophyta	0.0 (0.0)	0.0 (0.0)	0.0 (<0.1)	0.0 (0.0)	0.0 (0.0)	0.7 (0.2)
Xanthophyta	0.0 (0.0)	0.0 (0.0)	0.1 (0.1)	0 (0.0)	0.0 (0.0)	3 (3)
USEPA NLA
Total	0.0 (<0.1)	1 (1)	12 (20)	3 (4)	8 (16)	1300 (1300)
Cyanophyta	0.0 (0.0)	0.1 (0.1)	4 (5)	0.3 (0.3)	1 (2)	4309 (94)
Chlorophyta	0.0 (0.0)	0.0 (<0.1)	3 10	0.2 (0.3)	1.1 (1.3)	1310 (1310)
Diatom	0.0 (0.0)	0.0 (<0.1)	1.4 (1.3)	0.1 (0.1)	0.5 (0.7)	204 (32)
Cryptophyta	0.0 (<0.1)	0.0 (<0.1)	0.9 (1)	0.1 (0.1)	0.5 (0.5)	131 (48)
Dinoflagellate	0.0 (0.0)	0.0 (0.0)	2.1 (2.4)	0.0 (0.1)	1.0 (1.4)	436 (120)
Euglenoid	0.0 (0.0)	0.0 (0.0)	0.0 (0.7)	0.0 (0.0)	0.1 (0.1)	51 (43)
Chrysophyta	0.0 (0.0)	0.0 (0.0)	0.2 (0.1)	0.0 (0.0)	0.0 (0.0)	230 (6)
Xanthophyta	0.0 (0.0)	0.0 (0.0)	0.0 (<0.1)	0 (0.0)	0.0 (0.0)	2 (0.1)

Figure 1. Plots and regression equations for log₁₀-transformed total phytoplankton biovolume (mm³/L) versus log₁₀-transformed chlorophyll (µg/L) for all data and by location using paired samples from Denmark (N = 10,658), Florida (N = 318), and during the U.S. Environmental Protection Agency’s National Lake Assessment survey (N = 2187).

Figure 2. Plots and regression equations for log₁₀-transformed data points along the upper continuum of the total phytoplankton biovolume (mm³/L)–chlorophyll (µg/L) relationship for all data (left) and July/August data (right) for paired samples from Denmark (N = 10,658), Florida (N = 318), and during the U.S. Environmental Protection Agency’s National Lake Assessment survey (N = 2187).