Trophic status and nutrient regime of Cochin estuarine system, India

1395-1404The Cochin estuarine system (CES) being one among the world’s highly polluted and productive estuarine system was monitored to assess the trophic condition in view of the changing nutrient regime. The estuarine system was shallow, with mixo-oligo to mixo-mesohaline salinities (9.65 ± 6.99 ‰). The dissolved oxygen and the pH regime of the water column were 5.92 ± 1.13 mg L-1 and 7.42 ± 0.71, respectively. The study documents high dissolved inorganic nitrogen (28.95 ± 8.47 µmol L-1), dissolved inorganic carbon (1089.87 ± 362.36 µmol L-1), dissolved inorganic phosphate (7.76 ± 3.56 µmol L-1) and gross primary productivity (2.31 ± 1.14 gC m-3 day-1). However, explicitly augmented inorganic nutrients coupled with low dissolved oxygen, pH, and productivity patterns were observed in station 7. High dissolved inorganic carbon denoted net heterotrophic condition. Trophic index (TRIX units) was observed to be high compared to earlier reports, indicated eutrophicated condition with the highest value at station 1 (8.04 ± 0.28). Therefore, proper management interventions are required to restrict allochthonous nutrient loading to protect CES from further anthropogenic impacts and to mitigate the eutrophication process