Biochemical composition of zooplankton from Visakhapatnam harbour waters, east coast of India

Abstract

Proximate composition, zooplankton biomass, protein, lipid, carbohydrate, organic carbon and calorific content of mixed zooplankton in the Visakhapatnam harbour waters were estimated. Biomass varied from 15.2 to 74.0 ml.100 m -3 (X =31.05 ±17.7) in the outer harbour and 10 to 64.0 ml.100 m -3 ( X =26.30±14.8) in the inner harbour. Copepods, tintin-nids, decapods and chaetognaths formed dominant groups of total zooplankton ( > 90%) in the harbour waters throughout the year. Of the biochemical fractions of zooplankton, protein formed the major component, varied from 233.6 to 563 mg.g -1 (X=379.62±107), lipid varied from 61.2 to 181 mg.g -1 (X =103±32.7). Carbohydrate ranged from 65.5 to 127.4 mg.g -1 (X =85.78±16.92), organic carbon varied from 334.9 to 461.2 mg.g -1 (X=380.44±33.6) and calorific values varied from 2.2 to 5.4 (X =3.5±.94) k.cal.g -1 . Higher values of these constituents were observed during high saline premonsoon and postmonsoon periods when the population densities of copepods, tintinnids, decapods, chaetognaths were high. Significant positive correlations (P < 0.01) observed between calorific values, protein, lipid indicates to certain extent, that latter act as metabolic reserve of the zooplankton. Based on the results zooplankton do not have extensive lipid storage suggesting that protein in addition to the lipid may serve as metabolic reserve. Relatively higher calorific values were attributed to the dominance of copepods in the zooplankton population throughout the year.