Assessing the threat to Antarctic shallow marine ecosystems from hitchhikers on non-native kelp

长期以来，人类活动和航运一直被认为是对南极偏远和孤立的浅海生态系统“生物安全”的主要威胁（Chown et al., 2015）。然而，最近的研究表明，南大洋强大的绕极风、洋流和锋面可能不会成为北方自然殖民的障碍（Fraser et al., 2018）。亚南极（巴塔哥尼亚、福克兰群岛、新西兰和南半球的中纬度岛屿）浅水海洋环境的特点往往是在极其偏远的岛屿上高度暴露的海岸（Griffiths & Waller, 2016）。无冰的海岸线经常被浓密的海带（Durvillaea antarctica）、巨囊藻（Macrocystis pyrifera）和其他大型植物覆盖。长期以来，人们一直认为南极浅海沿岸海洋群落被数百公里的深海和南极环极流与亚南极邻居隔离开来。根据文献记载，在任何时候，南大洋都有超过7000万的海带筏漂浮在海面上（Smith, 2002）。这些有生命的浮动岛屿可以接待来自原始海岸和开阔海域的各种乘客物种。在风、洋流和风暴的推动下，这些木筏通常被认为是将新物种引入南极洲和亚南极岛屿的理论载体。我们在南极海滩上发现了非本地海带和各种“搭便车”的乘客生物，这使我们质疑这些物种扩散障碍的渗透性（Avila et al., 2020）。这是第一个非本地物种通过海带筏活着到达南极大陆的证据。其中一种旅客物种，即苔藓虫膜孔虫，在一些冷水地区被发现是一种入侵性的生态有害物种，这是它在南极洲的第一次记录（Avila et al., 2020）。成功的申请者将利用现有的数据和样本，利用科学考察（包括巴塞罗那大学在西班牙国家南极考察中的合作伙伴）、旅游船只和以前的考察，调查在智利南部、福克兰群岛、南乔治亚岛和南极洲的漂浮和搁浅的海带上发现的群落。候选人将在南大西洋进行实地考察，量化潜在的搭便车者，并进行生理实验。他们将与智利的合作者/伙伴（麦哲伦大学）和福克兰群岛的CASE伙伴（南大西洋环境研究所- SAERI）合作。该考生将：确定该地区两种主要的海带（Durvillaea antarctica和Macrocystis pyrifera）上生活的物种，以及它们在海带植物上的丰度和位置。检查海带被从岸边移走对生活在海带上的动植物的影响，模拟导致海带漂流的风暴的影响（在福克兰群岛使用水肺潜水，可能在麦哲伦智利进行）。利用分类学和分子方法研究海带物种的生物地理分布格局；并将其与海洋学模型和海带作为载体的作用联系起来。了解亚南极和福克兰岛本地物种现在和未来对极地锋以南条件的适应能力（使用生理实验和IPCC气候情景）。利用从博士学位中获得的知识，进行风险评估，告知科学家和政策制定者极地锋以南可能的候选物种和殖民中心，无论是现在还是将来。

Human activity and shipping have long been considered the principal threats to the "biosecurity" of the remote and isolated shallow marine ecosystems of Antarctica (Chown et al., 2015). However, recent work has shown that the Southern Ocean's strong, circumpolar winds, currents and fronts may not be a barrier to natural colonisation from the north (Fraser et al., 2018). The sub-Antarctic (Patagonia, the Falkland Islands, New Zealand and the mid-latitude islands of the Southern Hemisphere) shallow water marine environment is often characterised by highly exposed shores on extremely remote islands (Griffiths & Waller, 2016). The ice-free coastlines are often dominated by dense beds of the kelp Durvillaea antarctica, Macrocystis pyrifera and other large macrophytes. Antarctic shallow coastal marine communities were long thought to be isolated from their subAntarctic neighbours by hundreds of kilometres of deep ocean and the Antarctic Circumpolar Current.According to the literature, over 70 million kelp rafts are afloat in the Southern Ocean at any one time (Smith, 2002). These living, floating islands can play host to a range of passenger species from both their original coastal location and those picked in the open ocean. Driven by winds, currents and storms towards the coast of the continent, these rafts are often cited as theoretical vectors for the introduction of new species into Antarctica and the sub-Antarctic islands.Our discovery of non-native kelp and a wide range of 'hitchhiking' passenger organisms washed up on Antarctic beaches led us to question the permeability of these barriers to species dispersal (Avila et al., 2020). This is the first evidence of non-native species reaching the Antarctic continent alive on kelp rafts. One passenger species, the bryozoan Membranipora membranacea, is found to be an invasive and ecologically harmful species in some cold-water regions, and this is its first record from Antarctica (Avila et al., 2020).The successful applicant will investigate the communities found on floating and beached kelp from southern Chile, the Falkland Islands, South Georgia and Antarctica using existing data and samples, opportunistic collections by scientific expeditions (including partners from University of Barcelona on the Spanish National Antarctic Expeditions), tourist vessels and previous expeditions. The candidate will be expected to undertake a field campaign to the South Atlantic to quantify the potential hitchhikers and conduct physiological experiments. They will be working with collaborators/partners in Chile (University of Magallanes) and the CASE partner in the Falkland Islands (South Atlantic Environmental Research Institute - SAERI).The candidate will:Identify the species living on the two main species of kelp in the region, Durvillaea antarctica and Macrocystis pyrifera, and their abundance and location on the kelp plants.Examine the effect of kelp becoming dislodged from the shore on the fauna and flora that live on the kelp, simulating the effects of storms that lead to kelp rafting (undertaken using scuba diving in the Falkland Islands and potentially in Magellanic Chile).Investigate biogeographic distribution patterns in the species living on the kelp, using taxonomic and molecular methods; and relating this to oceanographic models and the role of kelp as a vector.Understanding the ability of sub-Antarctic and Falkland Island native species to tolerate conditions found south of the Polar Front both now and in the future (using physiological experiments and IPCC climate scenarios).Undertake a risk assessment, using knowledge gained from the PhD, to inform scientists and policy makers about the likely candidate species and centres of colonisation south of the Polar Front, both now and in the future.