Abstract:
This study has objectives to describe macrobenthic communities on sandy beaches at the Eastern Seabord. Community structure of macrobenthos, species diversity and biomass of macrobenthos were investigated. The relationship between macrobenthos and environmental parameters were also studies.This study were carried out on 18 beaches along the East coast of Thailand, namely; Bangsaen-wonnapha, Bangpha, Sriracha, Leamchabang, Pattaya, Bangsaray, Payon-namrin, Marrunpeung, suanson, Maepim, Kungwiman, Leamsadet, Jaolao, Leamsing, Larnsray, Mukkaew, Banchuien and Chanchon, Samples were collected during low-tide, sorted, identifed and weighed. Five groups of macrobenthos were found in this study : Polycheata, Crustacea, Gastopoda, Bivalvia, Echinodermata. An average abundance and biomass of all macrobenthos were 46.37 Bivalvia were the most dominant species in terms of both abundance (79.24%) and biomass (86.13%). When considering relationships between macrobenthos and environmental paranmeters, abundance and biomass has no relationship with organic matter, sand and water quality However, there is a positive relationship with coarse and fine sand and negative relationship with medium sand. The macrobenthos also have a positive relatioship with nitrate, nitrite, phosphate and silicate. Nontheless, they had a negative relationship with pH, salinity and temperature.There were significant differences on the distribution of macrobenthic communities on different beach types. On intermediate sandy beaches, which receive moderate wave activity highest densities of macrobenthos were found. In contrast, dissipative and reflective beaches have less macrobenthos. When considering zonation of macrobenthos on sandy beaches, on the upper part found fast moving and air breathing animals e.g. grost crab and isopod were dominant. On water line zone, the sand shells (Donax sp.) were the most abundant. On the surf zone, the dominant animals found were polychaetes, hermit crabs, bivalves and snails.