Composition and distribution of benthic macro fauna in Na Thap River, Songkla Province,Thailand.

An ecological study was carried out to determine the distribution and composition of benthic macro fauna in Na Thap River at Songkla Province,Thailand for three months (May till July) which is dried season. The aim of the present study was to provide a description of the benthic macro fauna along the 10 station at Na Thap River from the upstream towards downstream. The sampling of benthic macro fauna was done by using Ekman grab samlper with 23 x 25 cm² area for 10 stations along the river from upstream to downstream area. In total, 79 taxa from three phyla of benthic macro fauna were collected; namely; Annelida (polychaete), Molluscs (bivalve and gastropod), and Arthropod ( crustacea, malacostra and insecta). The total density of benthic macro fauna at all stations were 870 individuals/m². Both taxa diversity and density of benthic macro fauna show significant diffirences over sites(F=6.672,P<0.0001 and F=5.156,P<0.05, respectively). Based on benthic macro fauna studied at the downstream area which is St1 to St5, the most abundance species was Perenereis quadtrefagesi and Metilidae sp. followed by sternaspida sp. At the upstream area, nematodes were found at St 8 and Chironomus sp. only found at St 10. While the most distribution of mollusks found at St 9 and St 10 such as corbiluca sp. and Sermyla riquetii. Conversely, there are no organism collected from St 6 and St 7.