Abstract: In the spring of 2019, we collected sediment samples in four sections across 13 stations in the Dongwan mangrove wetland in Fangchenggang City, Guangxi, to investigate composition, abundance, and biomass of meiofauna. More than 11 meiofaunal groups were recorded,including free-living marine nematode, copepoda, polychaeta, oligochaeta, ostracoda, isopoda, bivalves, cumacea, halacaroidea, gastropods, cladocerans, and other unidentified groups. The mean abundance was (10364±8012) ind·10 cm^-2 across different sections. Nematodes were the absolutely dominant group, followed by copepods. The average abundance of nematodes was (9886±7746) ind·10 cm^-2, accounting for 95.38% of the total abundance of meiofauna, while that of copepods was (221±358) ind·10 cm^-2, accounting for 2.14% of the total. The meanbiomass of meiofauna was (10502±7894) μg·10 cm^-2 across different sections, with the descending sequence of Section 3 > Section 2 > Section 1 > Section 4.

Key words: sexual dimorphism, sexual selection, ecological adaptation.