A deep-sea perspective on coral resilience in a changing world

海洋正在经历大规模的物理、化学和生物变化，造成重大的生态系统变化。这种影响在当地社区、捕鱼业和科学家容易接近的浅层大陆架水域中显而易见（例如，珊瑚礁白化加剧，鱼类产量减少，有害藻类和水母大量繁殖）。深海的变化可能同样剧烈，具有同样具有挑战性的长期后果（例如，温度升高，pH值和氧气含量降低），特别是在高纬度地区。然而，这些变化对公众来说不太明显，而且由于进入深海的后勤挑战，长期以来一直没有得到充分的研究。尽管人们日益认识到深海的内在价值（如生物多样性、蓝碳储量）和经济价值（如天然药物、重金属资源、渔业苗圃），但我们对构成深海主要栖息地的生物的复原力和脆弱性的认识仍然存在明显差距。在这方面特别重要的是由钙化珊瑚形成的广泛的深海栖息地。这些珊瑚可以存活数千年，它们在一个令人惊讶的动态环境中形成了广阔多样的栖息地，在这里，食物供应由从表面落下的颗粒和不断变化的洋流控制。然而，海洋酸化、食物供应和氧气水平下降等变化有可能降低珊瑚有效生产骨骼的能力。如果珊瑚能够控制骨骼的组成，使其更能适应这些变化，这将是在快速变化的世界中生存的关键策略。尽管有迹象表明一些珊瑚可能有这种能力，但我们不知道是哪个分类群，或者在什么条件下，从而阻碍了有效的海洋保护策略。在这个项目中，我们打算比较三种栖息地形成的珊瑚分类群，它们表现出不同的骨骼生长模式，可能决定了它们对外部压力的脆弱性。软核菌能钙化文石，并能改变它们生长的海水，使它们能在低pH值的海水中生存。八瓣珊瑚的骨架是由方解石形成的，方解石比文石更耐溶解。针状星形藻具有由文石或方解石形成的能力，目前尚不清楚它们是如何在低pH值水域中生存的。令人惊讶的是，这些珊瑚的系统发育树受到的约束非常少，这使得评估分类群之间的关系甚至识别物种都具有挑战性。利用新的基因组和地球化学数据，加上对珊瑚在现代海洋中生长的方式和位置的系统检查，我们将处于一个独特的位置，以区分珊瑚生物矿化的内部生物控制与外部影响。我们拥有对深海珊瑚收藏的特殊访问权限，这将使我们能够建立第一个系统基因组框架，以了解矿化和对环境至关重要的外部压力的易感性，栖息地形成的深海珊瑚。这将帮助我们了解哪些深海珊瑚可能容易受到当前和未来气候变化的影响，以及珊瑚生长需要哪些环境参数。这些数据将用于更好地保护南大洋脆弱的海洋生态系统，通过向南极研究科学委员会提供投入，该委员会向南极条约协商会议提供客观和独立的科学咨询意见。

The ocean is undergoing large scale physical, chemical and biological changes which are causing major ecosystem-scale shifts. The impact is clearly evident in shallow continental shelf waters easily accessible to local communities, the fishing industry, and scientists (e.g. increased coral reef bleaching, dwindling fish yields, blooms in nuisance algae and jellyfish). Changes in the deep sea are potentially as dramatic, with equally challenging long-term consequences (e.g. rising temperatures and lowering pH and oxygen levels) especially in the high latitudes. However, these changes are less visible to the general public and are chronically understudied given the logistical challenges of access to the deep sea. Even with increasing recognition of the intrinsic (e.g. biodiversity, blue carbon storage) and economic value (e.g. natural pharmaceuticals, heavy metal resources, fisheries nurseries) of the deep sea, there remain glaring gaps in our understanding of the resilience and vulnerability of the organisms which make up the major habitats of the deep. Particularly important in this regard are the extensive deep-sea habitats formed by calcifying corals. These corals can live for thousands of years and they form vast, diverse habitats in a surprisingly dynamic environment where food supply is controlled by falling particles from the surface and ever-changing currents. However, changes such as ocean acidification, food supply, and declining oxygen levels have the potential to reduce the ability of corals to produce their skeletons effectively. If corals were able to manipulate the composition of their skeletons to be more resilient to these changes, this would represent a key survival strategy in a rapidly changing world. Despite hints that some corals may have this ability, we do not know which taxa, or under what conditions, thus hampering effective marine conservation strategies.In this project we intend to compare three habitat-forming coral taxa which exhibit contrasting modes of skeleton growth likely to dictate their vulnerability to external stress. Scleractinia calcify aragonite and are able to the modify seawater in which they grow so that they can live in low pH waters. Octocorals form their skeletons from calcite, which is more resistant to dissolution than aragonite. Stylasterids have the capacity to form from either aragonite or calcite, and as yet it is not known how they survive in low pH waters. Surprisingly, the phylogenetic tree for these corals is very poorly constrained, making it challenging to assess the relationships between the taxa or even to identify species. Using new genomic and geochemical data, together with a systematic examination of how and where corals grow in the modern ocean, we will be in a unique position to distinguish internal biological controls of coral biomineralization from external influences. We have exceptional access to deep-sea coral collections which will allow us to build the first phylogenomic framework for understanding mineralisation and susceptibility to external pressure in environmentally-critical, habitat-forming deep-sea corals. This will help us understand which deep-sea corals may be vulnerable to current and future climate change, and what environmental parameters are required for coral growth. These data will be used to better protect vulnerable marine ecosystems in the Southern Ocean via input to the Scientific Committee for Antarctic Research which provides objective and independent scientific advice to the Antarctic Treaty Consultative Meetings.