Benthic macrofauna

Abstract

The variability of macrofaunal assemblage in the Mandovi–Zuari, Goa, India estuarine complex was studied during 2002-2003 and compared with earlier data of the same area. Sediment samples in duplicate were collected from 15 stations using a van Veen grab. A total of 68 taxa were identified with polychaetes dominating in terms of abundance and diversity. Faunal density was the highest in Zuari estuary (582- 1911 ind m sup(-2)) than in the Mandovi, (663-1236 ind m sup(-2)). However, biomass was high in the Mandovi (5.59 -17.42 g m-2), mainly due to the presence of bivalves, than in the Zuari (3.38 -10.42 g m sup(-2)). Cossura sp. and Mediomastus sp. dominated during May 2002 and April 2003 while, Prinospio pinnata dominated during September 2003. The present data indicates a major change in the macrofaunal community compared to the earlier published literature. In 2002-03, the polychaete community was dominated by opportunistic species of family Capitellidae, Spionidae and Cossuridae compared to the carnivorous species belonging to family Eunicidae, Nephtyidae and Glyceridae in 1972-73. The fauna reduced from 1604 ind m sup(-2) (1972-73) to 573 ind m sup(-2) in 1992 but showed significant increase in 2002-03 (1073 ind m (sup(-2)). However, the numbers of species were reduced from 111 (1972-73) to 68 species (2002-2003). Many species, endemic to the estuarine system, were recorded in low abundance or were absent. Clam bed of Meretrix casta reported earlier from these estuaries, had very low abundance in 2002-03. It can be concluded that, the macrofaunal community in the Mandovi-Zuari estuary has changed during the last few decades but the reason is not clearly understood. Hence a detail investigation is necessary to understand the factors responsible for such changes.