Benthic communities and biodiversity in Thai mangrove swamps

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1. To elucidate the community structure and biodiversity of benthic animals in mangrove swamps, field studies were conducted at Klong Kone mangrove swamps in Samut Songkhram Province, Thailand from 1994 to 1996. We set 2 transect lines extending from mud flat to landward fringe of the mangrove forest. Organic matter in the sediments inside the forest were higher than those in the mud flat, but the nutrient concentrations in the interstitial water showed the opposite trend.2. We studied the benthic fauna by quantitative and qualitative samplings. In the outer mud flat and the transplanted area, the density increased during 2 years and Hypsicomus sp. (polychaete) and Apseudes sp. (tanaid crustacean) were dominant. In the mangrove forest, gastropods, polychaetes, ocypodid, sesarmid crabs and erobid snails were prominent, and the density and species richness were rather stable for 3 years. There was a general tendency for the number of individuals decrease from the mud flat to the inner part of the forest. However, diversity index showed the opposite trend.3. In the transplantation area, the saplings planted in 1994 grew to a height of about 5 m. Whit the growth of mangroves, the organic matter in the sediments increased. The number of species also increased from 1994 to 1996.4. For the studies of colonization processes of the barnacles, we set and monitored the plastic test poles at several different environments. The zonal distributions of Balanus sp. (occupying lower level) and Chthamalus sp. (upper) were observed, and population densities were higher at the mud flat than inside the forest.5. Comparison of the benthic communities between intact and deforested forests revealed that the existence of developed forests are important for the biodiversity conservation of benthic community. A research report of our project for 3 years is published.