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 (7° 6' - 7° 12' N; 79° 49' - 79° 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. DOI: 10.4038/sljas.v11i0.2222Sri Lanka J. Aquat. Sci. 11 (2006): 43-61

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This study provides the capability of mapping, monitoring distribution and changes of regional mangroves using remote sensing data. The study area located in Mekong delta, Vietnam. Landsat ETM+ and digital elevation model (DEM) were used to enhance the discrimination between mangrove and non-mangrove forests and MAD technique was used to assess the changes in the mangrove cover in study area. Results showed that information from satellite remote sensing can play a useful role in determining the changes in land area and mangrove cover in Mekong Delta, especially mangrove forests has been significantly reduced in Tra Vinh province during 2000-2005.