Abstract:

The biodiversity and diel variation of the species in benthic boundary layer (BBL) fauna were analyzed in samples collected, using a Midicorer, at four stations in a section of the Yellow Sea from Qingdao to Chejudo Island. Thirty-two species were identified from the samples, including 19 copepods, 3 amphipods, 3 cumaceans, 2 mysids, 2 chaetognaths, 2 cladocerans, and 1 euphausiid. These species could be sorted into three biological assemblages: mesozooplankton, macrozooplankton, and hyperbenthos. The main species included Euterpina acutifrons, Microsetella norvegica, Danielssenia sp.,Paracalanus parvus, and Acartia bifilosa. The hyperbenthos dominated the BBL fauna in abundance. Copepod larvae (nauplii and copepodites) also formed an important component. In these samples, the BBL fauna exhibited high evenness (0.728-0.915), low species number (19-33) and low diversity indices (2.248-2.827). The diversity index of hyperbenthos and mesozooplankton was higher than that of macrozooplankton. No significant difference was found in diversity of each assemblage between daytime and nighttime (t-test,P>0.05). The abundance of the BBL fauna at station 1－3 with fine sand sediments was lower than that at the other three stations with silt-clay sediments. Based on these two sedimentary conditions, the BBL fauna could be formed into two Bray-Curtis clusters joining at a distance of 26.6%. The Biota-Environment Matching (BIOENV) analysis showed that the species and abundance of the BBL fauna were correlated closely not only to water depth and bottom water temperature, but also to the vertical fluxes of particulate organic carbon and nitrogen in the near bottom layer and to the nature of the sediment particulates.