Diversity of macrobenthic community in the Negombo estuary, Sri Lanka with special reference to environmental conditions.

 

D.D.G.L. DAHANAYAKA* AND M.J.S. WIJEYARATNE

Abstract

Benthic animals are generally considered to be good indicators of environmental conditions of aquatic ecosystems. The present study was undertaken to study the spatial variation of macrobenthic community in Negombo estuary (70 6’ – 70 12’ N; 790 49’ – 790 53’ E), which is subjected to a variety of anthropogenic activities. Benthic samples were obtained from 25 randomly selected sites in Negombo estuary in March 2003 and the macrobenthos were separated by wet sieving and identified as much as possible. The diversity of macrobenthos was determined using Shannon-Wiener index and the similarities among the macrobenthic communities at different sites were determined using Bray-Curtis similarity coefficient. Seventy-six species of benthic invertebrates belonging to 41 families were recorded during the study. Of the gastropods, those belonging to families Assimineidae, Cerithiidae, Haminoeidae and Hydrobiidae were the most abundant. The most abundant polychaete families were Pilargidiidae and Heterospionidae. Among amphipods, aorids were recorded in most of the sampling sites. The sampling sites were separated into several clusters based on the diversity of macrobenthos. The major environmental factors that influenced the separation of these clusters appeared to be salinity, presence of mangroves and soil texture.

 

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