Hydrothermal activity and deep-ocean biology of the Mid-Cayman Rise

我们提议首次对世界上最深的海底火山脊进行调查，以获得全球深海生物拼图中至关重要的一块，促进我们对地球上最大生态系统中生物多样性模式的理解。我们的提案目标是中开曼隆起（MCR），这是一个海底火山山脊，在加勒比海形成海洋地壳。与迄今为止研究过的所有山脊一样，我们希望在MCR上找到热液喷口：支持丰富深海生物群落的温泉。在过去的30年里，对热液喷口的调查发现了数百种新的动物物种，并表明喷口比最初认识的要普遍得多。了解物种如何在这些不太可能的避风港中生存，已经彻底改变了生态系统如何提供能量的想法，甚至为生命起源提供了线索。但我们还不知道是什么控制着这些岛屿般的极端环境中物种的全球分布。例如，东太平洋的喷口是一米长的管虫的家园，但这些动物在大西洋中部的喷口却不为人所知。MCR提供了一个独特的机会来确定造成这种模式的因素。MCR与大西洋有深水连接，因此它的通风口可能栖息着与大西洋中脊有关的物种。但是在巴拿马地峡关闭之前，大约300万年前，也有一条与东太平洋的深水连接。因此，MCR可能拥有与东太平洋物种相关的物种，构成了两大洋之间的“缺失环节”。另外，由于其深度和与其他火山脊的隔离，MCR也可能拥有与其他地方发现的物种不同的物种。因此，表征其喷口群落应揭示洋流、地质历史、深度和隔离在确定喷口物种全球分布中的作用。由于我们对深海物种扩散的了解大多来自于对这些系统的研究，这将促进对深海生物多样性模式的理解。由于这一潜力，国际海洋生物普查已将MCR确定为调查的优先事项。通过与其他山脊的类比，我们还预计在MCR上存在多种类型的热液喷口。其中包括与海底山脉有关的高温系统，在海底山脉中，来自地幔的岩石可能被推过上面的地壳。我们还预计山脊上较冷的碱性喷口是由海水和暴露的地幔岩石之间的反应产生的。而靠近6000米最大MCR深度的喷口预计会有创纪录的高温和不寻常的地球化学，这是地壳中产生它们的反应的压力驱动差异的结果。这样的喷口极有可能产生适应它们的新动物物种和新微生物。因此，我们建议研究世界上最深的海底扩张中心的地质和水文，使用现有的技术来定位其约110公里长的所有热液喷口。这将包括使用NERC的新型Autosub 6000自动水下航行器来精确定位海底的通风口。然后，我们将与英国的深潜机器人飞行器Isis一起参观这些喷口，对它们的地质、地球化学和生物进行取样。分析这些样本将确认驱动喷口的地球化学过程，并揭示其居民与其他喷口的进化和遗传关系。我们还将为海洋微生物学和生物技术的国际计划收集样本，并通过外展计划与更广泛的公众分享我们的发现。通过首次使用尖端技术调查我们星球的这一部分，并回答深海科学中的一个关键问题，该提案解决了NERC在知识前沿提供世界级环境研究的目标

We propose to investigate the world's deepest undersea volcanic ridge for the first time to obtain a vital piece in a global jigsaw puzzle of deep-sea life, advancing our understanding of patterns of biodiversity in our planet's largest ecosystem. Our proposal targets the Mid-Cayman Rise (MCR), an undersea volcanic ridge where ocean crust is being created in the Caribbean Sea. In common with all such ridges examined so far, we expect to find hydrothermal vents on the MCR: hot springs that support rich communities of deep-sea life. Investigations of hydrothermal vents over past 30 years have found hundreds of new animal species and shown that vents are more common than originally realised. Understanding how species survive in these unlikely havens has revolutionised ideas about how ecosystems can be supplied with energy and even provided clues to the origins of life. But we have yet to understand what controls the global distribution of species in these island-like extreme environments. East Pacific vents, for example, are home to metre-long tubeworms, but those animals are not known at Mid-Atlantic vents. The MCR presents a unique opportunity to determine the factors responsible for such patterns. The MCR has a deep-water connection with the Atlantic, so its vents may be inhabited by species related to those of the Mid-Atlantic Ridge. But before the Isthmus of Panama closed ~3 million years ago, there was also a deep-water connection with the eastern Pacific. The MCR may therefore harbour species related to those of the eastern Pacific, constituting a 'missing link' between the two oceans. Alternatively, the MCR may also host species unlike any found elsewhere, as a consequence of its depth and isolation from other volcanic ridges. Characterising its vent communities should therefore reveal the roles of ocean currents, geological history, depth and isolation in determining global distributions of vent species. As much of what we know about the dispersal of deep-sea species in general comes from studying these systems, this will advance understanding of patterns of deep-sea biodiversity. Because of this potential, the international Census of Marine Life has identified the MCR as a priority for investigation. From analogies with other ridges, we also expect a variety of types of hydrothermal vent on the MCR. These include high-temperature systems associated with an undersea mountain where rocks from the Earth's mantle may be pushed through the overlying crust. We also anticipate cooler alkaline vents on the ridge, created by reactions between seawater and exposed mantle rocks. And vents towards the ~6000 m maximum MCR depth are expected to have record high temperatures and unusual geochemistry, as a result of pressure-driven differences in the reactions in the crust that create them. Such vents have a high potential for new animal species and novel microbes adapted to them. We therefore propose to study the geology and hydrography of the world's deepest seafloor spreading centre, using established techniques to locate all hydrothermal vents along its ~110 km length. This will include using NERC's new Autosub 6000 autonomous underwater vehicle to pinpoint vents on the seafloor. We will then visit those vents with the UK's deep-diving robotic vehicle Isis to sample their geology, geochemistry and biology. Analysing these samples will confirm the geochemical processes driving the vents and reveal the evolutionary and genetic relationships of their inhabitants to vents elsewhere. We will also collect samples for international programmes in marine microbiology and biotechnology and share our discoveries with the wider public through an outreach programme. By using cutting-edge technology to investigate this part of our planet for the first time and answer a key question in deep-sea science, this proposal addresses NERC's goal of delivering world-class environmental research at the frontiers of knowledge