Species abundance and water and sediment characteristics for three ANDEEP stations on Maud Rise and the Weddell Sea

The benthic fauna was investigated during the expedition ANT-XXIV/2 (2007/08) in relation to oceanographic features, biogeochemical properties and sediment characteristics, as well as the benthic, pelagic and air-breathing fauna. The results document that Maud Rise (MR) differs distinctly from surrounding deep-sea basins investigated during previous Southern Ocean expeditions (ANDEEP 2002, 2005). Considering all taxa, the overall similarity between MR and adjacent stations was low (~20% Bray-Curtis-Similarity), and analyses of single taxa show obvious differences in species composition, abundances and densities. The composition and diversity of bivalves of MR are characterised by extremely high abundances of three species, especially the small sized Vesicomya spp. Exceptionally high gastropod abundance at MR is due to the single species Onoba subantarctica wilkesiana, a small brooder that may prey upon abundant benthic foraminiferas. The abundance and diversity of isopods also show that one family, Haplomunnidae, occurs with a surprisingly high number of individuals at MR while this family was not found at any of the 40 bathyal and abyssal ANDEEP stations. Similarly, polychaetes, especially the tube-dwelling, suspension-feeder fraction, are represented by species not found at the comparison stations. Sponges comprise almost exclusively small specimens in relatively high numbers, especially a few species of Polymastiidae. Water-column sampling from the surface to the seafloor, including observations of top predators, indicate the existence of a prospering pelagic food web. Local concentrations of top predators and zooplankton are associated with a rich ice-edge bloom located over the northern slope of MR. There the sea ice melts, which is probably accelerated by the advection of warm water at intermediate depth. Over the southern slope, high concentrations of Antarctic krill (Euphausia superba) occur under dense sea ice and attract Antarctic Minke Whales (Balaenoptera bonaerensis) and several seabird species. These findings suggest that biological prosperity over MR is related to both oceanographic and sea-ice processes. Downward transport of the organic matter produced in the pelagic realm may be more constant than elsewhere due to low lateral drift over MR.

本研究于ANT-XXIV/2（2007/08）考察航次中针对底栖动物群落（benthic fauna）展开调查，并结合海洋学特征、生物地球化学属性、沉积物特征，以及底栖、浮游与空气呼吸类群的相关数据开展综合分析。研究结果表明，毛德海隆（Maud Rise, MR）与此前南大洋考察航次（ANDEEP 2002、2005）所调查的周边深海盆地存在显著差异。若考虑所有分类单元（taxa），毛德海隆与邻近站位的整体相似性较低（Bray-Curtis相似性约为20%）；单分类单元分析则显示，物种组成、丰度及密度均存在显著差异。毛德海隆的双壳类（Bivalvia）群落组成与多样性特征表现为三个物种的丰度极高，其中尤以小型Vesicomya属物种最为突出。毛德海隆腹足类（Gastropoda）的丰度异常偏高，主要由单一物种Onoba subantarctica wilkesiana贡献——该物种为小型育幼型类群，可能以大量存在的底栖有孔虫为食。等足类（Isopoda）的丰度与多样性分析同样显示，Haplomunnidae科在毛德海隆的个体数量异常偏高，而该科物种在ANDEEP航次的40个半深海-深渊站位中均未被采集到。与之类似，多毛类（Polychaeta）——尤其是管栖悬浮食性类群——的代表物种在对照站位中均未被发现。海绵动物（Porifera）几乎全部为小型个体，且相对数量较多，其中尤以Polymastiidae科的数个物种为代表。从表层至海底的水柱采样（包括顶级捕食者观测数据）表明，该区域存在繁荣的浮游食物网。顶级捕食者与浮游动物的局部高聚集区，与毛德海隆北坡发育的大规模冰缘水华密切相关。该区域海冰消融现象明显，中层水深的暖水平流作用可能加速了这一过程。在毛德海隆南坡，密集海冰下方存在高浓度的南极磷虾（Euphausia superba），这吸引了南极小须鲸（Balaenoptera bonaerensis）与多种海鸟聚集。上述研究结果表明，毛德海隆区域的生物繁盛现象与海洋学过程及海冰动态均存在关联。由于毛德海隆区域的侧向漂移较弱，浮游生境产生的有机质向下输送过程可能比其他区域更为稳定。