Benthic biodiversity of seamounts in the southwest Indian Ocean

西南印度洋海山的底栖生物多样性海山是生物多样性的中心，是深海的生态热点，但难以接近给研究带来了重大挑战。因此，存在明显的抽样差距，其中赤道地区和印度洋大部分地区是最广泛的。西南印度洋海脊(SWIR)是从印度洋中部延伸到南大洋中大西洋海脊的主要地质特征。它拥有丰富的海山，支持高产的深水渔业，但就生物多样性和生态系统功能而言，它是全球海洋采样最少的区域之一。我们建议研究西南大洋中部S 42°E至S 58°33°之间海山上从小型底栖动物到大型底栖动物的多样性和分布。这一区域的底栖生物完全没有被研究过，尤其令人感兴趣的是它与主要洋流的位置、初级生产力的梯度以及最近对全球冷水珊瑚分布的预测。该地区可以被认为是我们对全球海山动物群了解方面最大的差距。通过研究动物群落与生境类型的关系、种群的遗传关联性以及表层生产力、洋流和底栖生物分布之间的关系，我们将加深对海洋海山动物分布、丰度、多样性和演化过程的理解。一个新的基于环境生态位因子分析(ENFA)的栖息地适宜性模型预测，南印度洋低至2500米的硬质底质是冷水硬珊瑚的主要栖息地。我们建议通过将研究区域内珊瑚物种的分布和丰度与模型分布进行比较来检验这些预测。模型预测的确认将支持最近的担忧，即人为二氧化碳排放的增加可能会导致钙质海洋生物的活动范围发生变化。深海捕鱼业与联合国粮食及农业组织(粮农组织)合作最近提出了一项倡议，提议在SWIR上设立一些自愿的海底保护区，在这些保护区内不会进行底拖网捕捞：其中三个在拟议的研究区域内。这在国际水域是史无前例的事件，为研究《生物多样性公约》在保护深海生境和公海物种方面的效力提供了一个独特的机会。通过行业合作获得的关于研究地点捕捞努力的详细信息，将使我们能够评估拖网捕捞对缓慢生长的深海底栖生物组合的影响，并收集基线信息，以评估停止捕捞后的恢复过程。

Benthic biodiversity of seamounts in the southwest Indian Ocean Seamounts are centres of biological diversity and are ecological hotspots in the deep ocean but their inaccessibility poses major challenges for research. In consequence, there are conspicuous sampling gaps of which the equatorial regions and most of the Indian Ocean are the most extensive. The southwest Indian Ridge (SWIR) is a major geological feature which extends from the central Indian Ocean to join the Mid-Atlantic Ridge in the Southern Ocean. It is rich in seamounts and supports a productive deep-water fishery yet, in terms of biodiversity and ecosystem functioning, it is one of the least sampled regions of the global ocean. We propose to study the diversity and distribution of benthic assemblages, from meiofauna to megafauna, on seamounts in the central section of the SWIR between 41 degrees S 42 degrees E and 33 degrees S 58 degrees E. The benthos of this region is completely unstudied and is of particular interest in terms of its position in relation to major ocean currents, gradients of primary productivity, and recent predictions as to the global distribution of cold-water corals. The region may be regarded as the most significant gap in our understanding of the seamount fauna globally. By studying the associations between faunal assemblages and habitat types, the genetic relatedness of populations, and the relationships between surface productivity, currents, and benthic distributions, we will enhance understanding of the processes governing the distribution, abundance, diversity and evolution of fauna on oceanic seamounts. A new habitat-suitability model based on environmental niche factor analysis (ENFA) has predicted that hard substrata in the southern Indian Ocean, down to ca. 2,500 m, are prime habitats for cold-water scleractinian corals. We propose to test these predictions by comparing the distributions and abundances of coral species across the study area with modelled distributions. Confirmation of the model predictions would lend support to recent concerns that increases in anthropogenic carbon dioxide emissions are likely to cause range shifts in calcareous marine organisms. A recent initiative from the deep-sea fishing industry working with the United Nations Food and Agriculture Organisation (FAO) has proposed a number of voluntary benthic protected areas (BPAs) on the SWIR in which no bottom trawling will take place: three of these are within the proposed study area. This is an unprecedented event in international waters and presents a unique opportunity to study the effectiveness of BPAs in protecting deep-sea habitats and species in the high seas. Detailed information on fishing effort at the study sites, available through industry collaboration, will allow us to assess the effects of trawling on slow-growing deep-sea benthic assemblages, and to gather baseline information against which the process of recovery following cessation of fisheries can be assessed.