Community Structure And Secondary Productivity Of Macrozoobenthos In The Bering Sea And Their Correlation With Environmental Factors

The present study generally analyzed the macrozoobenthos samples and data collected during the Chineses Arctic Research Expedition cruise in year 1999, 2010, 2012 and 2014 in the Bering Sea combing the relevant literature and environmental factor parameters, and revealed the community structure, biodiversity, secondary productivity of macrozoobenthos as well as the spatial distribution of feeding functional groups in the Bering shelf, slop and basin. The study also studied main environmenal factors affecting macrozoobenthos under the background of global warming and human activities, and discussed the influences pelagic-benthic coupling and spatial heterogeneity may bring to the macrobenthos communities. The main research results are as followings:（1） 12 phylum and 239 species of macrozoobenthos were identified. Polychaetes, mollusca and crustaceans were predomiant taxa, which contained 110, 44, and 49 species respectively. Species were mainly consisted of northern cold water species-eurythermic species, which was quite different from that in the Southern Ocean where more endemic species were found. Main predominant species were Scoloplos armiger and Ceradocus capensis, but specific predominant species in different areas differed: in the shelf area, Scoloplos armiger, Ceradocus capensis and Echinarachnius parma were main predominant species, in the slope area, Ctenodiscus crispatus, Ophiura sarsii and Eudorella pacifica were main predominant species, while main predominant species in the basin area were Prionospio malmgreni, Dasybranchethus fauveli and Pilargis verrucosa. Macrozoobenhos density values and biomass values were between 0⁸400 ind/m² and 0-9890.9 g/m² respectively, indicating a decline trend from the shelf to the slope. Cluster analysis result showed that similarity among the macrozoobenthos communties in the study area was low. The communities presented a patchy distribution in the study area.（2） Benthic secondary productivity and P/B values ranged from 0 to 1879.7 k J·m^-2·a^-1 and 0.10 to 1.15 a^-1 respectively, and the average values were 220.6±341.5 k J·m^-2·a^-1 and 0.43±0.24 a^-1 respectively. Polychaetes and crustaceans were the main contributors to the secondary productivity and P/B values. Secondary productivity in different areas were rowed from high to low in order: 387.8±552.1 k J·m^-2·a^-1（northern shelf area）>213.1±90.0 k J·m^-2·a^-1（slope area） >131.6±130.1 k J·m^-2·a^-1（western shelf area）>131.6±130.1 k J·m^-2·a^-1（eastern shelf area）>1.0±1.1 k J·m^-2·a^-1（basin area）. Higher benthic secondary productivity appeared in the Bering shelf and slope, while that in the basin was lower.（3） The macrozoobenthos were categorized into five functional groups based on feeding types including the detritivorous group（D）, the camivorous group（C）, the planktophagous group（Pl）,, the omnivorous group（O） and the phytophagous group（Ph）, which contained 96, 68, 48, 19 and 8 species in the Bering sea, respectively.. Average abundance of different functional groups were rowed from high to low in order: D（427 ind/m²）>Pl（121 ind/m²）>C（118 ind/m²）>O（51 ind/m²）>Ph（43 ind/m²）. Average biomass of different functional groups were rowed from high to low in order: D（354.4 g/m²）>C（133.7 g/m²）>Pl（120.0 g/m²）>Ph（9.2 g/m²）>O（7.1 g/m²）. Predominant functional groups in the north shelf area were D and Pl, in the eastern and western shelf area, the predominant functional groups were C and D, while D were dominant in continental slope and basin.（4） Correlation analysis revealed that, biological parameters such as species number, diversity indices H’ and d, density and biomass had significant or extremely significant correlation with environmental factors such as water depth, median size, and clay proportion of sediments; Secondary productivity had significant correlation with water depth and sand proportion of sediments; Sediment organic matter, bottom temperature and salinity also influenced the distribution of macrozoobenthos.Study results showed that, along the depth gradients of shelf-slope-basin, water depth and sediments types were main factors that affected the macrozoobenthos comminity structure and secondary productivity distribution. Compared to silt% and clay%, habitat with higher sand% and silt% contained a macrozoobenthos with higher diversity, species number and secondary production. In the Bering shelf and slope, impacts from rich upper water and strong pelagic-benthic coupling accelerated the settlement of ice algae, plankton and other organic particles to the sea bed, resulting in high standing stock and biomas in this area. In contrast, in the basin area with thousand water depth, organic particles settled to the bottom greatly reduced, and therefore food supply to macrobenthos was extremely rare.