Table 2 Indicator threshold values to classify the trophic status of the Meghna River estuary.

From: Dominant phytoplankton groups as the major source of polyunsaturated fatty acids for hilsa (Tenualosa ilisha) in the Meghna estuary Bangladesh

Indicator parameter

Seasons

Classification System

Methods

References

Dry

Wet

Good*

Fair*

Poor*

Very poor*

DIN (mg/l)

0.29

0.36

0 to < 0.1

 ≥ 0.1 but < 1

 > 1

–

80th percentile45

Dodds45

DIP (mg/l)

0.59

0.45

0 to < 0.01

 ≥ 0.01 but < 0.1

 > 0.1

–

80th percentile45

 

Dissolved silica (mg/l)

5.1

8.1

 > 5

 > 2 but ≤ 5

 > 0 but ≤ 2

0

10th percentile46

Bricker et al.46

Phytoplankton biomass (µg/l)

5.6

6.8

0 to ≤ 5

 > 5 but ≤ 20

 > 20 but ≤ 60

 > 60

90th percentile43

Garmendia et al.43

  1. *Good = Oligotrophic; Fair = Mesotrophic; Poor = Eutrophic; Very poor = Hypereutrophic; UE = Upper estuary, ME = Middle estuary, LE = lower estuary, CK = Char Kukrimukri, HI = Hatiya Island.
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