Investigating Structural Changes In Reef-Associated Biodiversity Along A Natural Gradient In Ocean Acidification

最近的研究表明，二氧化碳溶解到海洋中造成的海洋酸化对海洋生物，特别是建造钙壳或骨骼的生物，如珊瑚，有广泛的负面影响。然而，大多数研究都集中在实验室环境中的有限数量的物种，因此忽略了许多间接的影响，起源于更复杂的物种相互作用，发生在自然界中。珊瑚礁比任何其他海洋生态系统都拥有更多的物种。此外，它们在经济上非常重要，提供食品和其他服务，如旅游景点和药品。由于珊瑚物种对海洋酸化的敏感性，珊瑚礁生态系统可能受到严重威胁，但我们仍然不知道整个珊瑚礁社区将如何应对。该项目将利用巴布亚新几内亚最近发现的自然酸化珊瑚礁系统，该系统沐浴在不同酸度的沃茨，包括与21世纪末全球预期的酸度相当的酸度。该项目调查海洋酸化对生活在珊瑚礁间隙中的动物生物多样性的影响。这些动物代表了珊瑚礁多样性的大部分;它们在珊瑚礁食物链中发挥着非常重要的作用，但人们对其了解甚少。利用DNA标记和照片分析，将对生活在三种不同酸度水平（目前、预计50年后、预计100年后）的神秘物种进行量化和识别，以阐明随着海洋酸化，珊瑚礁群落发生的变化。研究结果将扩大对海洋酸化后果的了解，并有助于对珊瑚礁进行更准确的监测和有效的管理策略。科学成果将在国际会议上分享，并发表在同行评审的期刊上，收集的数据将公开提供。该项目还将促进史密森学会的科学家、专业教育工作者和科学传播者与科学、技术、工程和数学（STEM）领域代表性不足的华盛顿高中生之间的积极合作。学生们将接受海洋酸化科学方面的培训，并将参与为史密森尼现场和在线观众开发推广产品，扩大史密森尼与公众分享这些成果的能力。海洋酸化（OA）现在正在影响脆弱的珊瑚礁生态系统，这些生态系统已经受到数十年的当地压力（例如，污染、过度捕捞）。许多实验室实验表明，低pH值对珊瑚礁生物的钙化、生长和繁殖产生有害影响。研究还强调了物种反应的差异，这取决于它们是单独测试还是在多物种组合中测试，这表明间接影响对OA敏感性的重要性，无法通过实验室实验进行评估。因此，热带海底浅层二氧化碳渗漏提供了宝贵的机会，通过提供珊瑚礁海景的自然pH梯度，评估长期暴露于低pH值对珊瑚礁的生态后果。其中包括巴布亚新几内亚米尔恩湾省的珊瑚礁，从正常到低pH值沃茨呈现出强烈的梯度，但在其他化学性质和温度方面与正常的珊瑚礁条件相似。迄今为止，包括米尔恩湾在内的大多数关于酸化珊瑚礁的工作都集中在珊瑚和其他明显的生物上。然而，绝大多数的珊瑚礁多样性是由生活在珊瑚礁结构内的未充分研究的神秘群落组成的。这些营养关键群体可能面临OA的风险，因为酸化珊瑚礁的典型三维复杂性降低，但数据很少。这项研究将测量这些社区在米尔恩湾珊瑚礁的pH梯度的结构变化。研究人员将研究在三个pH值范围内（常规~8.0，中等~7.8-7.9和低~7.6-7.8）部署的体积标准化采样结构的多样性模式，这些pH值范围涵盖了未来一百年的预测pH值范围。使用照片分析，以及较大的能动和无柄分类群的DNA条形码和大块无柄和小能动组分的元条形码，研究人员将评估整个pH梯度中存在的物种的空间覆盖范围，多样性和丰度。这项研究将检验以下假设：无脊椎动物的多样性将随着pH值的降低而减少，分类组成将转向对酸化沃茨更有抵抗力的群落（例如非钙化生物）。因此，该项目的总体目标是评估未来海洋酸化对与珊瑚礁生态系统相关的高度多样化的神秘动物可能产生的影响。这项研究对我们理解珊瑚礁的生态和根据全球变化制定管理战略都有影响。

Recent research has revealed that ocean acidification, caused by carbon dioxide dissolving into the ocean, has a broad range of negative consequences for marine organisms, especially organisms that build calcium shells or skeletons such as corals. However, most studies have focused on a limited number of species in laboratory settings and have therefore ignored the many indirect effects originating from more complex species interactions that occur in nature. Coral reefs harbor more species than any other marine ecosystem. Moreover, they are economically very important, providing food and other services such as touristic attractions and pharmaceuticals. Because of the sensitivities of coral species to ocean acidification, reef ecosystems are potentially severely threatened, but we still have no idea how entire reef communities will respond. The project will take advantage of a recently discovered, naturally acidified coral reef system in Papua New Guinea that is bathed by waters of variable levels of acidity, including levels comparable to those expected globally by the end of the 21st century. This project investigates the consequences of ocean acidification for the biodiversity of animals that live cryptically within the interstices of coral reefs. These animals represent the bulk of coral reef diversity; they play very important roles in the reef food chain but are poorly understood. Using DNA markers and photo analysis, cryptic species living at three different acidity levels (present day, expected in 50 years, expected in 100 years) will be quantified and identified in order to elucidate the changes occurring in coral reef communities as oceans acidify. Results will broaden understanding of the consequences of ocean acidification and allow for more accurate monitoring and effective management strategies for coral reefs. Scientific results will be shared at international conferences and published in peer-reviewed journals, and data collected will be made publicly available. The project will also foster active collaborations among scientists, professional educators, and science communicators from the Smithsonian Institution and Washington DC high school students underrepresented in Science, Technology, Engineering and Math (STEM) fields. The students will be trained in ocean acidification science and will be involved in developing outreach products for Smithsonian onsite and online audiences, expanding the ability of the Smithsonian to share these results with the general public.Ocean acidification (OA) is now affecting the fragile coral reef ecosystems already impacted by decades of local pressures (e.g., pollution, overfishing). Numerous laboratory experiments have shown deleterious effects of low pH on calcification, growth, and reproduction of reef organisms. Studies have also highlighted differences in species' responses depending on whether they are tested alone or in multi-species assemblages, suggesting the importance of indirect effects in sensitivity to OA that cannot be assessed from laboratory experiments. For this reason, shallow tropical submarine carbon dioxide seeps provide invaluable opportunities to assess the ecological consequences of long-term exposure to low pH for coral reefs in situ by providing a natural gradient in pH across reef seascapes. Among these are the reefs at Milne Bay Province, Papua New Guinea, which exhibit a strong gradient from normal to low pH waters but otherwise resemble normal reef conditions in terms of other chemical properties and temperature. Most work to date on acidified reefs, including at Milne Bay, has focused on corals and other conspicuous organisms. However, the vast majority of reef diversity is comprised of the understudied cryptic communities living within the reef structure. These trophically crucial groups are likely to be at risk from OA due to reduction in three-dimensional complexity typical of acidified reefs, but there are scant data. This research will measure structural changes in these communities across the well-characterized pH gradients of the Milne Bay reefs. The investigators will study diversity patterns in volumetrically standardized sampling structures deployed at three pH regimes (regular ~8.0, medium ~7.8-7.9 and low ~7.6-7.8) spanning the pH range predicted over the next one hundred years. Using photo analysis, and DNA barcoding of the bigger motile and sessile taxa and metabarcoding of the bulk sessile and small motile fractions , the investigators will evaluate spatial coverage, diversity and abundance of the species present across the pH gradient. The study will test the hypothesis that invertebrate diversity will decrease with decreasing pH and that taxonomic composition will shift to a community more resistant to acidified waters (e.g. non-calcifiers). Thus, the project's overall goal is to assess the likely impacts of future ocean acidification on the highly diverse cryptic fauna associated with coral reef ecosystems. This research has implications for both our understanding of the ecology of coral reefs and management strategies in the light of global changes.