Table 1 Monthly values (mean ± SD) of water parameters at seven sampling sites from January to December of 2015 in Tai Lake

WT (°C)

17.6 ± 8.7

18.8 ± 9.0

17.3 ± 9.1

17.6 ± 8.8

17.1 ± 8.4

18.6 ± 8.9

18.7 ± 8.3

0.999

pH

8.22 ± 0.34

8.49 ± 0.42

8.16 ± 0.46

8.11 ± 0.42

8.18 ± 0.44

8.48 ± 0.33

8.29 ± 0.29

0.113

SD (m)

0.33 ± 0.05

0.40 ± 0.08

0.27 ± 0.08

0.32 ± 0.04

0.30 ± 0.03

0.38 ± 0.07

0.37 ± 0.05

< 0.0001***

DO (mg/L)

9.8 ± 1.8

10.7 ± 1.5

10.2 ± 1.5

10.1 ± 1.7

9.92 ± 1.70

10.2 ± 1.6

9.08 ± 1.54

0.336

Conductivity (ms/m)

45.9 ± 8.5

50.1 ± 5.4

40.2 ± 8.5

49.0 ± 13.8

42.0 ± 7.0

50.5 ± 5.6

48.6 ± 7.7

< 0.05*

COD_Mn (mg/L)

3.6 ± 0.8

4.8 ± 0.7

3.8 ± 0.8

4.9 ± 1.0

3.6 ± 0.6

4.6 ± 0.7

4.0 ± 0.7

< 0.0001***

BOD₅ (mg/L)

1.4 ± 0.5

3.0 ± 1.3

2.1 ± 1.4

3.4 ± 1.4

1.6 ± 0.3

2.6 ± 0.7

2.8 ± 0.7

< 0.0001***

TN (mg/L)

1.44 ± 0.68

1.97 ± 1.11

1.75 ± 1.07

2.67 ± 1.05

1.39 ± 0.73

1.69 ± 0.64

1.88 ± 0.74

< 0.05*

NH₄⁺-N (mg/L)

0.07 ± 0.04

0.10 ± 0.05

0.103 ± 0.105

0.228 ± 0.229

0.08 ± 0.06

0.10 ± 0.06

0.21 ± 0.14

< 0.05*

TP (mg/L)

0.04 ± 0.02

0.07 ± 0.04

0.06 ± 0.03

0.10 ± 0.02

0.05 ± 0.02

0.06 ± 0.03

0.06 ± 0.02

< 0.0005***

Chl a (μg/L)

7.25 ± 4.58

69.2 ± 109

16.2 ± 2.4

64.1 ± 7.6

24.2 ± 44.6

14.8 ± 6.6

13.9 ± 7.7

< 0.0005***

COD_Cr (mg/L)

20 ± 5

25 ± 7

19 ± 5

25 ± 9

19 ± 6

25 ± 6

20 ± 6

0.065

F⁻ (mg/L)

0.621 ± 0.079

0.632 ± 0.076

0.615 ± 0.100

0.636 ± 0.104

0.607 ± 0.102

0.639 ± 0.065

0.553 ± 0.043

0.123

As (mg/L)

0.0017 ± 0.008

0.0029 ± 0.0024

0.0019 ± 0.0006

0.0026 ± 0.0019

0.0019 ± 0.004

0.0027 ± 0.0021

0.0023 ± 0.0014

0.760

Cu (mg/L)

0.0039 ± 0.0033

0.0049 ± 0.0055

0.0034 ± 0.0028

0.0044 ± 0.0037

0.0035 ± 0.0027

0.0048 ± 0.0057

0.0043 ± 0.0046

0.998

Pb (mg/L)

0.0043 ± 0.0058

0.0056 ± 0.0037

0.0028 ± 0.0033

0.0044 ± 0.0053

0.0042 ± 0.0061

0.0050 ± 0.0044

0.0073 ± 0.0066

0.425

MC-LR (μg/L)

0.069 ± 0.036

0.352 ± 0.349

0.091 ± 0.039

0.242 ± 0.196

0.098 ± 0.058

0.234 ± 0.281

0.116 ± 0.081

< 0.005**

NPR

55.7 ± 45.4

48.6 ± 63.0

32.1 ± 19.0

28.0 ± 13.4

33.1 ± 19.4

48.2 ± 62.9

35.2 ± 15.8

0.690

STSI

49.3 ± 3.3

57.6 ± 6.3

54.0 ± 4.7

61.0 ± 5.1

52.5 ± 4.0

54.5 ± 2.7

54.1 ± 2.5

< 0.00005***

Trophic state

Mesotrophication

Eutrophication

Eutrophication

Supereutrophication

Eutrophication

Eutrophication

Eutrophication

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