Where are the jellyfish? An integrative molecular study to reveal the gelatinous zooplankton species diversity, distribution, and connectivity within a changing Southern Ocean

胶质浮游动物（GZP）是由刺胞动物、栉水母和被囊动物组成的并系类群，具有生态多样性。GZP因其“水母水华”而臭名昭著，这可能对海上人类活动和海洋生态系统结构产生有害影响。然而，最近发生了一种范式转变，这也是GZP的广泛重要性和惠益的基础，从在浮游营养网中发挥关键作用转变为提供重要的生态系统服务，通过“瀑布”对碳泵作出贡献。在南大洋，环境变化导致某些地区微型浮游动物食草动物从磷虾到海鞘的丰度变化。除了广泛研究的salp，还有一个相当大的知识差距，其他SO GZP类群。这种知识差距主要是由于传统的网调查不适合研究这些脆弱的生物体。因此，该项目的主要目标是整合分子方法来表征SO GZP的物种多样性，分布和种群连接性，并将其与环境参数联系起来。在第一个目标中，将使用环境DNA分析来确定GZP物种组成的特征，以及它如何与不同的水团联系在一起。在海洋沉积物中发现的eDNA的物种组成也将与上覆水柱的物种组成进行比较，以更好地了解GZP在碳泵中的作用。在第二个目标中，将采用基于采样标本的地理分析来回答与SO GZP相关的遗传多样性和连接性问题。将测试种群是否是绕极的以及南极极锋对基因流动的作用。在第三个也是最后一个目标中，将使用三维生态位模型来模拟SO GZP的分布范围并确定其限制因素。建立这一基线信息将是至关重要的，以预测环境变化将如何影响GZP社区的组成和分布，并因此，它将如何影响营养网络和SO碳泵在未来。

Gelatinous zooplankton (GZP) are a paraphyletic and ecologically diverse planktonic group comprising cnidarian, ctenophores, and tunicates. GZP are notorious for their “jellyfish blooms”, that can have detrimental impacts on human activities at sea and on the structure of marine ecosystems. Recently, a paradigm shift has however occurred, also underlying the widespread importance and benefits of GZP, from playing a key role in the trophic pelagic web, to providing an important ecosystem service with their contribution to the carbon pump through “jelly-falls”. In the Southern Ocean (SO), environmental changes have led in some areas to an abundance shift in microzooplankton grazers from krill to salps. Besides the extensively studied salp, there is still a considerable knowledge gap on other SO GZP taxa. This knowledge gap is primarily due to traditional net surveys being unsuitable to study these fragile organisms. Therefore, the main goal of this project is to integrate molecular methodologies to characterize the species diversity, distribution, and population connectivity of SO GZP and to link these to environmental parameters. In the first objective, environmental DNA (eDNA) analyses will be used to characterize the GZP species composition and how it can be linked to different water masses. The species composition of the eDNA found in marine sediments will also be compared with those of overlaying water column, to better understand the role of GZP in the carbon pump. In a second objective, phylogeographic analyses based on sampled specimens will be employed to answer genetic diversity and connectivity questions related to SO GZP. Whether populations are circumpolar and the role of the Antarctic Polar Front against gene flow will be tested. In a third and final objective, ecological niche modelling in three dimensions will be used to model the distribution range of SO GZP and define their limiting factors. Establishing this baseline information will be crucial to predict how environmental change will affect the GZP community composition and distribution, and by consequence, how it will impact trophic networks and the SO carbon pump in the future.