The productivity of Cochin estuary and the adjacent backwater have been discussed in the light of significant contribution by periphytic algae. 'Ihe annual organic production by periphyton has been estimated to be 92,000 tonnes of carbon, the rate being 1.4 gC/m2/day. This is almost equal to the planktonic production. 'Ihe values of Net Daily Metabolism (NDM) and Assimilation Number (AN) of peuphyton in the backwater indicate relatively a mo:e productive photosynthetic assemblage.

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