Spatial distribution patterns of the mega-epibenthos on the continental shelves off the northern Antarctic Peninsula studied from OFOS seabed images taken during POLARSTERN cruise ANT-XXIX/3 (PS81) 2013

The epibenthos of the Southern Ocean shelves plays a significant role in marine ecosystem functioning, including biodiversity processes, but information on its composition, distribution and ecological drivers is still scarce. Here, we report results of a first study on the relationship between the spatial patterns of 18 systematic or functional groups and environmental factors, conducted in the waters off the northern Antarctic Peninsula during RV Polarstern cruise XXIX/3 (PS81) in January-March 2013. To comparatively address this issue at three nested spatial scales, seabed imaging surveys were performed along 28 photographic transects of 2 km length each at water depths from 70 to 770 m in three ecoregions (northwestern Weddell Sea, southern Bransfield Strait and southern Drake Passage), which differ in general environmental setting, primarily oceanographic characteristics and sea-ice dynamics. At a regional (100-km) scale, epibenthic assemblages differed significantly from each other in all three ecoregions, whereas at an intermediate 10-km scale, differences among depth-related habitat types (bank, upper slope, lower slope, deep/canyon) were less pronounced. These regional and intermediate spatial patterns were superimposed by a marked small-scale (10-m) patchiness of epibenthic distribution within the 2-km transects. Obvious correlation between mega-epibenthos and environmental factors (e.g., temperature, salinity, oxygen, sea-ice cover, seabed ruggedness) was found especially for large scales of >2 km.

南大洋陆架的底上生物（epibenthos）在海洋生态系统功能（包括生物多样性过程）中发挥着关键作用，但目前关于其组成、分布及生态驱动因子的相关信息仍较为匮乏。本研究首次探讨了18个分类学或功能类群的空间分布格局与环境因子的关联，调查区域位于南极半岛北部周边海域，数据采集于2013年1-3月极星号（RV Polarstern）第XXIX/3航次（PS81）的科考作业期间。为在三级嵌套空间尺度下对比分析该科学问题，研究团队在三个环境背景（主要为海洋学特征与海冰动力学存在显著差异的生态区）内开展了海底成像调查：共设置28条长度为2km的摄影样带，调查水深范围为70~770m，涉及的三个生态区分别为威德尔海西北部、布兰斯菲尔德海峡南部以及德雷克海峡南部。在区域尺度（100km）下，三个生态区内的底上生物群落均存在显著差异；而在中等尺度（10km）下，与水深相关的生境类型（浅滩、上陆坡、下陆坡、深水区/峡谷）之间的差异则相对不显著。上述区域与中等尺度的空间分布格局，叠加了2km样带内显著的小尺度（10m）底上生物分布斑块性。研究发现，大型底上生物（mega-epibenthos）与环境因子（如温度、盐度、溶解氧、海冰覆盖度、海底粗糙度）之间存在显著关联，且该关联在大于2km的大空间尺度上尤为明显。