Collaborative Research: Defying Dissolution: Unraveling the Enigma of North Pacific Deep-Sea Scleractinian Reefs in Undersaturated Water

与浅水珊瑚一样，深海珊瑚提供的结构和栖息地支持着不同的无脊椎动物群落和具有商业价值的鱼类物种。然而，由于海洋酸化影响了表层和深海的水化学，深海珊瑚礁的未来非常不确定，因为海洋酸化使珊瑚更难建立这些生态系统所依赖的三维结构。北太平洋自然恶劣的水化学条件正因海洋酸化而加剧，因此以前认为该区域不可能发生深海珊瑚礁发育。尽管有这些预期，但最近在夏威夷群岛西北部和皇帝海山链发现了珊瑚礁，其中7个地点中有4个对组成深海珊瑚礁的珊瑚骨架具有腐蚀性或可能溶解。随着这些珊瑚礁的发现，我们有了一个前所未有的机会来调查海洋酸化对这些重要生态系统的潜在影响，因为与之前的研究不同，我们的研究地点在相同深度存在水化学梯度。这项研究将解决有关深海珊瑚礁发育的基本问题，包括：深海珊瑚礁能否在对珊瑚骨骼具有腐蚀性的水中发育？在有利的水化学条件下发育的珊瑚礁，一旦遇到腐蚀性水，它们的命运是什么？珊瑚礁能在腐蚀性水中存活多久？通过解决这些问题，这项研究将为深海珊瑚礁的形成、持久性、分布以及海洋酸化对深海珊瑚群落的影响提供关键的见解。调查人员与美国国家海洋和大气局S深海珊瑚研究与技术计划以及北太平洋渔业委员会和国际海底管理局等在该地区积极为海山深海珊瑚社区制定管理决策的机构建立了合作伙伴关系。结果将通过出版物、向博物馆捐赠的珊瑚收藏品和公共数据库广泛分发给科学界。该项目将通过培训一名代表性不足的博士后科学家、三名研究生和本科生研究人员，帮助培养一支多样化和具有竞争力的STEM劳动力队伍。与WhaleTimes，Inc.的合作将包括用于潜入深度计划的ROV远程呈现、K-12学校访问和电子书。尽管人们期望深海珊瑚礁不可能在北太平洋恶劣的碳酸盐化学条件下存在，但最近在夏威夷群岛西北部和皇帝海山链发现了珊瑚礁，其中7个地点中有4个位于文石未饱和的水域。这些珊瑚礁的发现为研究海洋酸化对这些重要生态系统的潜在影响提供了前所未有的机会。更好地了解文石饱和度在深海珊瑚礁分布中的作用变得至关重要，因为已有文献证明，由于海洋酸化，文石饱和层(ASH)正在整个世界海洋中变浅。在不久的将来，随着文石饱和度的下降和火山灰浅滩的出现，更多的深海珊瑚礁将经历饱和不足，这使得深海珊瑚礁及其支持的具有生态和经济价值的生态系统的未来非常不确定。在西北大西洋珊瑚礁和海生委发现深海珊瑚礁的基础上，这个项目的首要问题是：深海珊瑚礁如何能够出现在远低于假定的珊瑚礁发育极限的不饱和水域中？虽然个别珊瑚可能能够在不饱和水域中钙化，但由于深海钙化速度缓慢，而且大多数珊瑚礁基质都是容易溶解的死骨，因此不太可能形成三维珊瑚礁结构。因此，要检验的假设是：1)这些深海珊瑚礁在饱和水中发育，现在处于不饱和水域，因为火山灰已经变浅；2)不饱和水域中的珊瑚礁现在是净溶解的；3)除文石饱和度外，其他环境参数正在驱动珊瑚礁的分布。为了验证这三个假设，我们计划进行两次研究巡航，以表征跨越文石饱和梯度的九座海山的珊瑚礁和环境参数，其中珊瑚礁存在于火山灰之上和之下。将收集珊瑚和水样，水下机器人将进行视频横断面调查，并将在珊瑚礁地点部署实验溶解区块和现场仪器，以调查：从海底(原位仪器)到百年(骨骼硼同位素作为pH替代指标)尺度上的碳酸盐化学变异性、钙化和溶解速率以及珊瑚礁生态。此外，物种分布模型将被用来检查决定这些深海珊瑚礁分布的环境因素。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Like their shallow-water counterparts, deep-sea corals provide structure and habitat that support a diverse community of invertebrates and commercially important fish species. However, as ocean acidification impacts the water chemistry of the surface and deep ocean, the future of deep-sea reefs is highly uncertain because ocean acidification makes it more difficult for corals to build the three-dimensional structure that these ecosystems depend on. The naturally harsh water chemistry conditions of the North Pacific are being exacerbated by ocean acidification therefore it was previously thought that deep-sea coral reef development could not occur in the region. Despite these expectations, reefs were recently discovered in the Northwestern Hawaiian Islands (NWHI) and the Emperor Seamount Chain (ESC), with 4 of 7 sites in waters that are corrosive to, or likely to dissolve, the coral skeletons that make up deep-sea reefs. With the discovery of these reefs, we have an unprecedented opportunity to investigate the potential impact of ocean acidification on these important ecosystems because, in contrast to previous studies, there is a gradient of water chemistry across our study sites, all at the same depth. This study will address basic questions regarding reef development in the deep sea, including: Can deep-sea coral reefs develop in water that is corrosive to coral skeletons? What is the fate of reefs that developed under supportive water chemistry conditions once they experience corrosive water? How long can reefs persist in corrosive water? Through addressing these questions, this study will provide critical insights into deep-sea reef formation, persistence, distribution, and the effects of ocean acidification on deep-sea coral communities. The investigators have a track record of partnerships with NOAA?s Deep-Sea Coral Research and Technology Program, and with the agencies actively making management decisions in this region for seamount deep-sea coral communities including the North Pacific Fisheries Commission and the International Seabed Authority. Results will be broadly circulated to the scientific community through publications, coral collections contributed to museums, and public databases. This project will contribute to developing a diverse and competitive STEM workforce through training of an underrepresented postdoctoral scientist, three graduate students, and undergraduate researchers. A partnership with WhaleTimes, Inc. will include ROV telepresence for the Creep into the Deep Program, K-12 School Visits, and e-books. Despite expectations that deep-sea scleractinian reefs could not exist under the harsh carbonate chemistry conditions of the North Pacific, reefs were recently discovered in the Northwestern Hawaiian Islands (NWHI) and the Emperor Seamount Chain (ESC), with 4 of 7 sites in waters undersaturated with respect to aragonite. The discovery of these reefs, with more than half the sites in undersaturated water, provides an unprecedented opportunity to investigate the potential impact of ocean acidification on these important ecosystems. It is becoming critical to gain a better understanding of the role of aragonite saturation in the distribution of deep-sea scleractinian reefs because it has been documented that the aragonite saturation horizon (ASH) is shoaling throughout the world oceans due to ocean acidification. More deep-sea reefs will experience undersaturation in the near future as aragonite saturation declines and the ASH shoals, making the future of deep-sea reefs and the ecologically and economically valuable ecosystems they support highly uncertain. Building on the discovery of deep-sea coral reefs in the NWHI and ESC, the overarching question of this project is: How is it that deep-sea scleractinian coral reefs can occur in undersaturated water, well below the hypothesized reef development limit Although individual corals may be capable of calcifying in undersaturated water, it is unlikely that a three-dimensional reef structure could develop since deep-sea calcification rates are slow and most of the reef matrix is dead skeleton susceptible to dissolution. Therefore the hypotheses to be tested are: 1) These deep-sea reefs developed in saturated water and are now in undersaturated water because the ASH has shoaled; 2) The reefs in undersaturated water are now net dissolving; and 3) Environmental parameters other than aragonite saturation are driving reef distribution. To test these three hypotheses, we plan two research cruises to characterize the reefs and environmental parameters of nine seamounts across an aragonite saturation gradient where reefs exist above and below the ASH. Coral and water samples will be collected, an ROV will conduct video transect surveys, and experimental dissolution blocks and in situ instrumentation will be deployed at the reef sites to investigate: carbonate chemistry variability on diel (in situ instruments) to centennial (skeletal boron isotopes as a pH proxy) scales, calcification and dissolution rates, and reef ecology. Further, species distribution modeling will be used to examine the environmental factors that determine the distribution of these deep-sea reefs.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.