Controls of Wind-Driven Jet on the Distribution of Pelagic Cnidarians in the Midwestern South China Sea

The coastal water transported by the combined action of southwest wind jet and anticyclonic eddy substantially influences the biological processes in the midwestern South China Sea. However, how the wind-driven jet affects the zooplankton community remains unclear. In this study, the species number, abundance, and vertical distribution of medusae were investigated in the wind-driven jet (WJR) and non-wind-driven jet regions (NWJR). The low-salinity and nutrient-rich coastal water substantially influenced species composition, abundance, and vertical distribution of medusae in the WJR. The species number of the meroplanktonic hydromedusae in the WJR was approximately twice that in the NWJR due to the horizontal transport of wind-driven jets. The abundances of holoplanktonic hydromedusae in WJR were 38.2 ± 9.3 ind⋅m–3, which were thrice of that in the NWJR regions, caused by the abundant diet in the WJR. Additionally, only the abundance of medusae above the thermocline was affected by the coastal water in WJR, while these showed no significant difference below the thermocline between the WJR and the NWJR. Generalized additive model analyses suggested that the diet was the most important factor affecting the abundance of the holoplanktonic hydromedusae and siphonophore, whereas meroplanktonic hydromedusae were influenced by the combination of temperature, salinity, and diet.

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Temporal and spatial distribution of the meiobenthic community in Daya Bay, South China Sea

Ocean Science Discussions ◽

10.5194/osd-9-1853-2012 ◽

2012 ◽

Vol 9 (2) ◽

pp. 1853-1885 ◽

Cited By ~ 1

Author(s):

L. Tang ◽

H. X. Li ◽

Y. Yan

Keyword(s):

South China Sea ◽

Vertical Distribution ◽

South China ◽

Spatial And Temporal Variation ◽

Daya Bay ◽

Total Abundance ◽

Temporal And Spatial Distribution ◽

Bottom Water Temperature ◽

China Sea ◽

Significant Difference

Abstract. Spatial and temporal biodiversity patterns of the meiobenthos were studied for the first time in Daya Bay, which is a tropical semi-enclosed basin located in the South China Sea. The abundance, biomass, and composition of the meiobenthos and the basic environmental factors in the bay were investigated. The following 19 taxonomic groups were represented in the meiofauna: Nematoda, Copepoda, Polychaeta, Oligochaeta, Kinorhyncha, Gastrotricha, Ostracoda, Bivalvia, Turbellaria, Nemertinea, Sipuncula, Hydroida, Amphipoda, Cumacea, Halacaroidea, Priapulida, Echinodermata, Tanaidacea, and Rotifera. Total abundance and biomass of the meiobenthos showed great spatial and temporal variation, with mean values of 993.57 ± 455.36 ind cm−2 and 690.51 ± 210.64 μg 10 cm−2, respectively. Nematodes constituted 95.60 % of the total abundance and thus had the greatest effect on meiofauna quantity and distribution, followed by copepods (1.55 %) and polychaetes (1.39 %). Meiobenthos abundance was significantly negatively correlated with water depth at stations (r=−0.747, P<0.05) and significantly negatively correlated with silt-clay content (r=−0.516, P<0.01) and medium diameter (r=−0.499, P<0.01) of the sediment. Similar results were found for correlations of biomass and abundance of nematodes with environmental parameters. Polychaete abundance was positively correlated with the bottom water temperature (r=0.456, P<0.01). Meiobenthos abundance differed significantly among seasons (P<0.05), although no significant difference among stations and the interaction of station × season was detected by two-way ANOVA. In terms of vertical distribution, most of the meiobenthos was found in the surface layer of sediment. This pattern was apparent for nematodes and copepods, but a vertical distribution pattern for polychaetes was not as obvious. Based on the biotic indices and analyses of their correlations and variance, the diversity of this community was likely to be influenced by environmental variations.

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