Abstract:
Status and ecological studies of sandy beaches on the East Coast of Thailand were carried out during 1999-2000. A total of 18 beaches from 4 provinces in the east of Thailand: Chonburi, Rayong, Chantaburi and Trat, were investigated on their macro benthic communities and also some physical and chemical factors. There were 40,572 individuals of macro benthos were collected where average abundance was 185 individuals/m2. A total of 76 taxon from 5 groups; Polychaeta, Crustacea, Gastropoda, Bivalvia and Echinoderamata were identified. Bivalvia was the most diverse and abundance found in the study area. There was a spatial variation on macro benthic community which sandy beaches on the inner part of the Thailand accommodate more diverse and abundance community than those on the Gulf of Thailand have course sand while the outer part had fine sand. This result indicated the different wave influence between areas. There was a variation on the nutrient concentration of interstitial water among beach. Generally, nutrient concentration were low in most beaches excepted Bang Pra and Sriracha where phosphate, silicate and also organic matter in the sediment were relatively very high. At Bangsean and Wonnapha, nutrient concentration was relatively low but organic matter was high. This result indicated different effects from terrestrial influence. Sandy beaches in the east of Thailand can be classified into three types as reflective, intermediate and dissipative beaches. Reflective beach has narrow littoral zone where macro benthic community is relatively less abundance where Prayoon, Namrin and Sangchantra are included in this group. Intermediate beach has narrow drying zone and wide surf zone where macro benthic community is relatively abundance where all sandy beaches in Chonburi and Trat are in this group. Lastly, dissipative beach has wide drying zone but narrow surf zone where microbenthic community is moderate abundance where Maerumpung, Suanson and Maepim are in this group. In general, factors that have strong influence on type of sandy beach and benthic communities were wave. Local influences can also be noticed where ground water can increase nutrient input to the sandy beach and also surrounding water.