Studies on the community structures of meiofauna and marine nematode at six stations in the Southern Yellow Sea,China

Meiofauna (0.031–0.5 mm) were sampled and studied at a grid of six stations during the cruise of investigation for over winter ground of anchovy (Engraulis japonicus) in the Southern Yellow Sea, China in January 2003. Total meiofauna individuals averaged (1.162±0.347) × 10⁶ ind m^?2 and the corresponding biomass 1.748 ± 0.72 g dwt m^?2 with the maximum 2.35g dwt m^?2 at Station 9594 and the minimum 0.537g dwt m^?2 at Station 11794. A total of fourteen taxa were identified. Free living marine nematodes were the most dominant group with an average abundance of (1.026 ± 0.206) × 10⁶ ind m^?2, accounting for 88.5% of total numbers, and an average of 85.4% lived in the surface layer (0–2 cm) of sediments. The individual dry weight was calculated, which ranges from O.Ol µg to 31.32f*g with an average of 0.261 µg. One hundred and forty two species or taxa of free-living marine nematodes belonging to 89 genera, 24 families and 4 orders were identified. Six of them were new species. The common dominant species were Dorylaimopsis rabalaisi, Sphaerolaimus balticus, Sphaerolaimus minitus, Metalinhomoeus longicauda, Prochromadorella attenuata., Campylaimus sp. 1, Vasostoma sp. 1, Daptonema normandicum, Paramonohystera riemanni, and Promonhystera sp.1. According to cluster analysis of Primer 5.0, the six stations were clustered into 2 groups with similar species composition at 40% similarity. The species diversity index (J), evenness index (d) and species richness index (d) of nematode were calculated and analyzed. Correlation analysis with respect to environmental factors showed that the abundance of meiofauna had a significant correlation with the median diameter of sediment (Md_ø). The species richness of nematodes had a highly significant correlation with Chl-a and significant correlations with Pha-a and Chl-a + Pha-a.