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

区域气候变化在南极，特别是在南极半岛地区得到了充分的证实。人们对气候变化的潜在驱动因素及其物理后果的细节越来越了解。海洋系统物理特性的变化对生物组成部分特别重要，其中除其他外包括海洋温度和海洋酸化的变化、季节性海冰的范围和时间的减少以及冰架和冰川的退缩和崩塌。然而，对生物系统的影响仍然知之甚少，首先，物理变化如何迅速地通过海洋食物网串联起来。因此，重要的是建立有利于长期比较的生态研究，以便对气候变化的未来后果进行预测。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，冰架崩塌特别重要，因为它为生物定植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等人最近的一篇综述强调了南极半岛周围冰架和沿海冰川50年来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。一般来说，现有冰架下的动物群处于贫营养、类似深海的条件下，由于冰架崩塌可能导致更大的营养输入，因此可能通过物种的损失和增加而改变群落结构。冰架的损失将使海洋积雪和底栖-远洋耦合水平增加，这将改变底栖养分循环，并可能导致额外的碳储存。此外，陆源物质也可能沉积在其中一些栖息地，可能影响现有的底栖动物，并改变未来殖民的条件。南极大陆架的底栖生物群落表现出高度的巨人症、长寿、生长缓慢、成熟晚和地方性，这意味着许多物种容易受到干扰。然而，这些社区也可能比目前所假设的更具活力，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地方性的高水平意味着社区进程将在一系列地点之间有所不同。在物种开始消失或未来的殖民化之前，尽早看到群落将是关键。在冰架消失后形成的南极冰架生态系统将很容易受到邻近地区物种的殖民；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（比现在更温暖的时期）出现的物种返回创造机会。我们的项目将使用四方面的方法：1)描述以前在A68下的底栖生物群落的特征，它们的组合和空间分布在与前冰架前缘距离相关的巢状尺度范围内。2)样品返回英国（保存在乙醇，RNAlater中，或保存在-80℃），用于将来的分子遗传学和基因组学分析，系统地理学，进化史和宏基因组学。3)利用δ 13C、15N和34S的体积稳定同位素对沉积物中冰藻、浮游生物和有机物等大型和巨型动物和食物源进行收集，并进行脂质分析。4)在海上进行体外孵育，探索多管微型环境中水生小动物和大型动物对13C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.