Benthic biodiversity under Antarctic ice-shelves - baseline assessment of the seabed exposed by the 2017 calving of the Larsen-C Ice Shelf

在南极，特别是在南极半岛地区，区域气候变化是确定无疑的。人们对气候变化的潜在驱动因素及其物理后果的详细情况越来越了解。海洋系统物理特性的变化对生物组成部分特别重要，除其他外，包括海洋温度和海洋酸化的变化、季节性海冰范围和时间的减少以及冰架和冰川的退缩和崩溃。然而，对生物系统的影响仍然知之甚少，首先是物理变化如何迅速通过海洋食物网级联。因此，必须开展有利于长期比较的生态研究，以便对气候变化的未来后果作出预测。这些研究最好在没有其他人类活动造成任何影响的情况下进行。在这方面，冰架崩塌具有特别重要的意义，因为它为生物定居和生态演替开辟了新的栖息地，并影响了已建立的生物地球化学循环。Trathan等人最近的一项综述强调了南极半岛周围冰架和沿海冰川50年的退缩如何暴露出至少2.4 x10^4 km^2的新开放水域。这些新发现的栖息地似乎允许新的浮游植物大量繁殖，随后迅速出现新的海洋浮游动物和海底群落。一般而言，现有冰架下的动物群存在于贫营养、类似深海的条件下，而且由于冰架崩塌可能导致更多的养分输入，因此可能会通过物种的增减而改变群落结构。冰架丧失将导致海洋积雪和底栖-中上层耦合增加，从而改变底栖营养循环，并可能导致碳储存增加。此外，陆源物质也可能沉积在其中一些生境中，对现有的底栖生物产生潜在影响，并改变未来殖民化的条件，南极大陆架的底栖生物群落表现出高度的寄生性、寿命长、生长缓慢、成熟晚和特有性，这意味着许多物种容易受到干扰。然而，这些社区也可能比迄今所假设的更具活力，即使在相对较短的时间内，也可能显示出惊人的变化速度。然而，它们仍然容易受到环境变异和变化的影响。因此，持续的气候变化的区域性质加上高度的地方性意味着社区进程将在一系列地点之间有所不同。在物种开始丧失或未来的殖民化之前，尽早发现群落将是关键，在冰架丧失后形成的南极大陆架生态系统将容易受到来自紧邻地区的物种的殖民化;然而，其他复杂的过程也可能发生，因为洋流可能为最后一次间冰期出现的物种创造返回的机会，我们的项目将采用四个方面的方法：1）描述以前在A68下的底栖生物群落，它们的组合和空间分布，在一系列嵌套尺度上与以前的冰架前缘的距离有关。2)返回英国的样本（保存在乙醇、RNAlater中，或储存在-80 ℃），用于未来的生物地理学、进化历史和宏基因组学的分子遗传学和基因组学分析。3）收集大型和巨型动物和食物来源，如冰藻、浮游生物和沉积物中的有机物，用于使用δ 13 C、15 N和34 S的大量稳定同位素进行食物网分析，4）在海上进行体外培养，以探索多芯管微观世界中底栖小型和大型动物对13 C的吸收。

Regional climate change is well established in the Antarctic, particularly in the Antarctic Peninsula region. Details of the underlying drivers of climate change and its physical consequences are increasingly well understood. Changes in the physical properties of the marine system are especially important for biological components and include, inter alia, changes in ocean temperature and ocean acidification, reductions in the extent and timing of seasonal sea-ice and the retreat and collapse of ice shelves and glaciers. Nevertheless, the implications for biological systems remain poorly understood, above all, for how rapidly physical changes might cascade through marine foodwebs. It is therefore important that ecological studies that facilitate long-term comparisons are established, and in order to develop projections of the future consequences of climate change. These studies are best undertaken in the absence of any effects caused by other human activities. In this respect, ice-shelf collapse is of special importance as it opens up new habitats for biological colonisation and ecological succession, and impacts established biogeochemical cycles.A recent review by Trathan et al. highlighted how 50-years of retreat in ice shelves and coastal glaciers around the Antarctic Peninsula has exposed at least 2.4 x10^4 km^2 of new open water. These newly revealed habitats appear to have allowed new phytoplankton blooms that were rapidly followed by new marine zooplankton and seabed communities. In general, the fauna under existing ice shelves exists in oligotrophic, deep-sea-like conditions and, because ice shelf collapse may lead to greater nutrient input, there may be a shift in community structure through the loss and gain of species. Ice-shelf loss will allow increased levels of marine snow and benthic-pelagic coupling that will alter benthic nutrient cycling and may result in additional carbon storage. Further, terrigenous material may also be deposited in some of these habitats, potentially impacting upon the existing benthos and modifying conditions for future colonisation.The benthic communities of the Antarctic shelf show high levels of gigantism, longevity, slow growth, late maturity and endemism, meaning that many species are susceptible to disturbance. However, these communities are also potentially more dynamic than so far assumed and can show surprising rates of change, even over relatively short time periods. Nevertheless, they remain susceptible to environmental variability and change. Therefore, the regional nature of ongoing climate change coupled with the high levels of endemism mean that community processes will vary across a range of sites. Gaining early sight of communities will be key, prior to the commencement of species loss, or future colonisation.The Antarctic shelf ecosystems that form following ice-shelf loss will be susceptible to colonisation by species from immediately adjacent areas; however, other complex processes may also take place as ocean currents may create opportunities for species to return that were last present in the last interglacial, a warmer period than at present.Our project will use a four-fold approach:1) Characterisation of the benthic community formerly under A68, their assemblages and spatial distribution at a range of nested scales in relation to the distance from the former ice-shelf front. 2) Samples returned to the UK (preserved in ethanol, RNAlater, or stored at -80C) for future molecular genetic and genomic analysis of phylogeography, evolutionary history and metagenomics.3) Collection of macro- and megafauna and dietary sources such as ice-algae, plankton and organic matter in the sediment for food web analysis using bulk stable isotopes of delta 13C, 15N and 34S, and lipid analysis.4) In-vitro incubation whilst at sea to explore 13C uptake by infaunal meio- and macrofauna in multicorer-tube microcosms.