Communities and coexistence of benthos in northern limb of Cochin backwaters

Abstract

Occurrence and coexistence of benthic communities of 9 stations in the northern limb of Cochin backwaters where an industrial belt (mostly chemical industries) is located are studied. Polychaetes with 30 species are the most common among groups present at all the stations. Capitella capitata which showed high density near the effluent discharge site is proposed as an indicator of pollution. Dendronereis aestuarina present at all stations and in high densities at sts 5, 6 and 8, can be considered as a pollution resistant species. Lycastis indica, Paraheteromastus tenuis, Telehspia annandalei, chironimid larvae and Pendora flexosa present at st 8, even-though in very low numbers, can be treated as pollution tolerant species. The number and the size of the clusters show a steady decline from sts 1 to 8. Maximum affinity is for adjacent stations and never exceeded 60%. Negative affinity indices obtained are deemed indicative of the varied environmental conditions. Results indicate limited spatial migration and possible niche separation.