Vertical distribution of polychaetes in brackishwater pond of Nethravathi estuary, India.

Vertical distribution of polychaetes in a semi-enclosed brackishwater pond of Nethravathi estuary was studied for one year from February 2004 to January 2005. The semienclosed brackishwater pond is a shallow water body with an average depth of 1-1.5 m with an area of 12 ha having direct connection with the estuary which opens into the Arabian sea. A total of nine species of polychaetes were identified. Among these, Dendronereis aestuarina and D. arborifera were most common and accounted for 65.62% of total abundance. The fauna were more abundant at 5-10 cm depth than at 0-5 cm depth and decreased beyond 10 cm depth. Species composition and the abundance of polychaetes were generally high during postmonsoon followed by premonsoon and monsoon season. Polychaete abundance showed positive significant correlation with organic carbon content at all depth layers of sediments in all the stations.