Studies On Ecology Of Meiofauna And Systematics Of Free-living Marine Nematodes In The Southern Yellow Sea, China

The benthic environment, the abundance, the biomass and production, the community structure and biodiversity of meiofauna and systematics of free-living marine nematodes were quantitatively studied at a grid of twenty two stations during the cruise of investigation for over winter ground of anchovy (Engraulis japonicus) in the Southern Yellow Sea, China in January 2003. The main results are as follows:Sedimentary grain size and the distribution of sediment type were analyzed. The sediment type of the stations mainly belongs to silt - clay or clay - silt. The grain size and the component of sediment influenced the contents and distributions of chlorophyll-a, phaeopigments and organic matter. The average concentration of chlorophyll-a in surface (0~2cm) and subsurface sediment (2~5cm) are 0.399±0.179 mg/kg sediment and 0.211±0.141 mg/kg sediment, respectively. The contents of phaeopigments in surface (0~2cm) and subsurface sediment (2~5cm) are 1.609 ± 0.812 mg/kg and 0.959 ± 0.581 mg/kg respectively. The average content of organic matter is 2.75%±1.12%. The correlations between the sedimentary environment factors were significant.A total of fifteen groups of meiofauna: nematoda, copepoda, polycheata, ostracoda, kinorhyncha, bivalve, gastropoda, gastrotricha, turbellaria, ophiuroidea, halacarida, hydrozoa, tanaidancea, amphipoda and cumacea were identified at 22 stations in this cruise. Nematode is the dominant group, accounting for 87.1% of total number of meiofauna, with copepoda in the second, accounting for 4.4%. The mean abundance, biomass and production of meiofauna were 954±289 ind/10 cm~2, 1054.2±491.0μg dwt/10cm~2 and 9487.8±4415.0 ug dwt/10 cm~2· a, respectively, and 81.5% of total number lives in the surface layer (0-2 cm) of sediments. The mean abundance ofnematode is 831 ±247 ind /10 cm2, which accounts for 87.1% of total number of meiofauna, and 80.1% of which lives in the surface layer (0-2 cm) of sediments. Compared with the abundance and biomass of other studies in and outside the Chinese waters, results of the Southern Yellow Sea is close to each other in having the same magnitude. The correlations among the numbers of meiofauna, nematodes and some environmental factors were analyzed.The proportion of four feeding types of nematode varies at different stations, but the deposit feeders (2A) are the dominant type and account for more than 50%. The nematode individuals are identified as females, males and juveniles in this study. Generally the number of juveniles accounts for above 60% of total number of nematodes. The ratio of females to males is 1.27(±0.3): 1. The individual average dry weight of nematode is different given different authors. The individual average dry weight of nematodes at selected six stations in the Southern Yellow Sea varied from 0.01 |ig to 31.32 ug, averaging 0.261 ug, lower than 0.4ug which incited by other authors in the references. The community structure of nematodes was studied. Clustering analysis showed that the community structures at different stations are divided into two groups, and belong to the cold water community of the subtidal muddy.The sheldon size spectra, biomass size spectra and normalized biomass spectra of the Southern Yellow Sea were constructed. The patterns of size spectra are similar at different stations. Two peaks occur at ESD 125-500 um and 8-16 mm respectively. It is separated by typically low valley at 0.5-1 mm. Normalized biomass spectra are constructed to compare the productivity of different ecosystems, and the production of zoobenthos of four studied stations was calculated by means of the normalized biomass spectra.Two hundred and twenty-three species (or taxa) of free-living marine nematodes belonging to 145 genera, 32 families and 4 orders are identified. Two genera and eighteen species of them were new to science. Name list of nematodes in the Southern Yellow Sea was given. Two new genera: Abelbolla gen. nov., Paramphimonhystrella gen.nov. and eighteen new species: Abelbolla boucheri sp. nov., Abelbolla huanghaiensis sp. nov., Abelbolla warwicki sp. nov., Belbolla huanghaiensis sp. nov.,Belbolla stenocephalum sp. nov., Belbolla warwicki sp. nov., Curvolaimus filiformis sp. nov., Trichotheristus articularus sp. nov., Oncholaimus multisetosus sp. nov., Sabatieria stenocephalus sp. nov., Setosabatieria coomansi sp. nov., Paramicrolaimus boucheri sp. nov., Terschellingia major sp. nov., Halalaimus longiamphidus sp. nov., Leptolaimodes decorus sp. nov., Paramphimonhystrella elegans sp. nov., Paramphimonhystrella minor sp. nov. and Paramphimonhystrella sinica sp. nov. were described and illustrated, respectively.