e - poz 2 - Central Institute of Brackishwater Aquaculture

nutrient regimen in the water and sediment phases of Cochin backwaters inrelation to other environmental features. Murthy and Veerayya (1972) gave adetailed account d the phosphorous content in the sediments of the Vernbanadlake. Eswara Prasad (1982) has described the. sediment features of m e prawnfarming a- adjacent to the Vembanad lake. A similar study in the prawn fieldsin and around Cochin backwaters is also presented by Aravindakshan et a/. (1992).Purandara and Dora (1987) had studied the textural characteristics and organicmatter of the near shore and surface sediment samples of the Vembanad lakebetween Azhikode in the North and Alappuzha in the South. One majorcontribution was by Sarala Devi (1989) and Sarala Devi et a/. (1992) on thetemporal and spatial distribution of the particulate organic carbon and particulatematter in Coch~n backwaters, especially in the lower reaches of the Periar rlver.Seralathan et a/. (1993) analysed and presented their findings on the features of thesediment and the distribution of organic carbon in the Cochln harbour area. .PLANKTON : One major area of ecological investiagtions in the Vembanad lakewas the qualitative and quantitative distribution of the plankton populat~on.Studies have been conducted on the variation and distribution of phytoplanktonand the factors affecting its production. One of the earliest report In this contextwas of George (1958) who has given an account of the general.composrtlon of theolankton from the Cochin backwaters. Subseauent important contribut~ons were;hose of Qasim and Reddy (1967) on the conientratio" of chlorophyll, Qas~m etal. (1969) on the organic production, Qasim et al. (1974) on the contribut~on ofmicroplankton and the nannoplankton, Gopinathan (1972) on the planktonbiomass, Gopinathan et a/. (1974), and Joseph and Pilla~ (1975) on the total cellcounts and the spatial and temporal distribution of the phytoplankton, .Quantitative and qualitative cmpos~tion of plankton In Vembanad lake extend~ngfrom Cochin to Alappuzha has been investigated by several authors (Devassy andCopmathan 1970, Devassay and Bhattathiri 1974, Kumaran and Raz 1975,Gopalakrlshnan et a/. 1988). The phytoplankton were exclusively studled byGopinathan (1972) in the Cochin backwaters where he reported the presence of62 species of Bacillariophyceae, 24 species of Dinophyceae, 3 specles ofMyxophyceae and 2 species of Cilioflagellates.