Meiofaunal composition on intertidal sandy beaches in Rayong Province, Thailand

In this study, the abundance and community composition of meiofauna on intertidal sandy beaches were investigated at four beaches in Rayong Province, Eastern Gulf of Thailand. A total of 12 meiofauna taxa were identified, of which nematodes was the most dominant (47.96%), followed by gastropods (13.34%) and copepods (8.04%). The highest values of Margalef’s taxon richness (d) and Shannon-Wiener diversity (H′) were found at Mae Ramphueng Beach with values of 1.44±0.25 (min=0.99, max=1.87) and 0.69±0.14 (min=0.37, max=0.94), respectively. In this study, seven families of meiobenthic copepods were identified, while no copepods were found at Saeng Chan Beach. Meiofaunal densities across the four sites ranged from 1 to 426 ind. 10 cm−2, with an average of 104.16±10.60 ind. 10 cm−2. The highest density was recorded at Mae Ramphueng Beach (196.80±28.75 ind. 10 cm−2), while the lowest was observed at Sang Chan Beach (15.56±3.81 ind. 10 cm−2). Spatial variation among the study sites was significant (F=28.01, p<0.01). Permutational MANOVA revealed significant differences in the meiofaunal composition among the four study sites (p<0.01), with Sang Chan Beach showing the most different community structure. Canonical analysis of principal coordinates (CAP) indicated that grain size, sea surface temperature (SST), and organic matter content were the key environmental factors influencing meiofaunal composition. This study provides essential baseline data on marine meiofauna in Thailand, supporting future ecological research.