RUI: Dissolution Mortality of Juvenile Bivalves in Coastal Marine Deposits.

虽然在理解控制无脊椎动物向底栖群落补充的因素方面取得了重大进展，但关于幼体后双壳类幼体极端死亡的原因仍存在许多问题。现在人们普遍认为，碳酸盐不饱和是温带、沿海、富含有机物质的表层沉积物中的一个共同特征，这些沉积物以底栖生物为主，那里的许多生物都有碳酸钙壳。这种不饱和可能会使新近定居的幼年双壳类很难形成壳，因此壳的溶解可能是幼体双壳类死亡的一个重要来源。如果是真的，这将对海底群落的招募、生存以及早期成岩过程与海底群落的形式和功能之间的耦合产生重要的影响。在这项研究中，圣约瑟夫学院的一位PI将进行一项多方面的研究，该研究将：(1)确定沉积物-水界面的碳酸盐饱和状态对潮间带泥浆中幼体双壳类从幼体向新幼体过渡后的招募和存活的影响，(2)评估控制这些相同泥浆中饱和状态的化学(反应)和生物(运输)过程，(3)建立基于阶段的耦合双壳贝壳溶解死亡的阶段/成岩模型，在由于碳酸盐循环中的变化而导致碳酸盐饱和的情况下。将对具有商业价值的物种Mya arenaria和Mercenaria ureenaria进行研究。野外工作将在缅因湾卡斯科湾的两个地点进行，这两个地点的生物学和成岩特征不同，但都有大量的梅塞纳里亚和Mya。现场研究将集中在Mya和Mercenaria的队列监测以及碳酸盐矿物饱和状态对幼体丰度变异性的影响。“沉积物缓冲”实验将被用来辨别紧跟在SET之后的表层沉积物的CaCO3缓冲是否通过限制幼体的外壳溶解来防止不饱和。通过现场比较，可以检验溶解死亡率作为生物和成岩环境的函数的重要性。在每个地点内的低水位和潮间带中上高度进行采样，将检查溶解死亡率作为潮汐暴露的函数的变异性。实验室实验将人工调节表层沉积物的饱和状态，从而调节双壳类幼体的栖息地，同时保持上覆水中的过饱和条件。溶解死亡率实验将确定“阈值”饱和状态，低于该饱和状态，特定大小类别的甲壳和Mya(2.0毫米)的外壳溶解死亡率发生。额外的实验室实验将结合直接观测和水槽实验来确定双壳类对不同饱和状态的沉积物表面的即时反应。来自野外和实验室的集体结果将被用来模拟由于碳酸盐循环的人为和自然变化而导致的两个物种的溶解死亡的情景。这项研究的广泛影响包括极强的教育成分和重要的社会效益。缅因州圣约瑟夫学院是一所本科院校，学生中约有70%是女性。让学生沉浸在研究中，将建立在PI以前的职业奖项的基础上，并促进学生参加和/或在国内/国际会议上展示研究成果，作为手稿的合著者。提高对双壳类幼体死亡率的了解可对沿海渔业的管理产生重要影响。最后，这项研究将把沿海双壳幼体种群与具有碳酸盐贝壳的公海浮游生物和珊瑚放在一起，目前预计这些浮游生物在贝壳形成和随后的死亡方面存在类似的问题。

ABSTRACTProposal # OCE-0622999Despite major advances towards understanding the factors controlling invertebrate recruitment to benthic communities, many questions remain regarding causes of the extreme juvenile mortality of post-larval bivalves. It is now widely recognized that carbonate undersaturation is a common feature in temperate, coastal, organic-rich surface sediments that are dominated by deposit feeding benthos where many organisms have calcium carbonate shells. Such undersaturation may make it difficult for recently settled, juvenile bivalves to form their shell, and so shell dissolution could represent a significant source of mortality for juvenile bivalves. If true, there would be important implications for benthic community recruitment, survivorship, and the coupling between early diagenetic processes and benthic community form and function. In this research, a PI from St. Joseph's College will conduct a multi-faceted study that will: (1) determine the effect of carbonate saturation state at the sediment-water interface on recruitment and survivorship of juvenile bivalves following their transition from pediveligers to new juveniles in intertidal mud, (2) evaluate the chemical (reaction) and biotic (transport) processes that control saturation state in these same muds and, (3) develop coupled stage-based/diagenetic models of juvenile bivalve shell dissolution mortality under "scenarios" of carbonate saturation due to variability in the carbonate cycle. Studies will be conducted on the commercially valuable species Mya arenaria and Mercenaria mercenaria. Fieldwork will be conducted at two sites in Casco Bay, Gulf of Maine, that differ in their biological and diagenetic characteristics, yet both have substantial sets of Mercenaria and Mya. The field research will focus on cohort monitoring of Mya and Mercenaria and the effect of carbonate mineral saturation state on the variability in juvenile abundance. "Sediment buffering" experiments will be used to discern if CaCO3 buffering of surface sediments immediately following the set prevents undersaturation by limiting external shell dissolution of juveniles. The site comparisons will permit examination of the importance of dissolution mortality as a function of both the biotic and diagenetic setting. Sampling at low water and mid-upper intertidal heights within each site will examine variability in dissolution mortality as a function of tidal exposure. Laboratory experiments will artificially regulate surface sediment saturation state, and thus juvenile bivalve habitat, while maintaining supersaturated conditions in the overlying water. Dissolution mortality experiments will determine "threshold" saturation states below which external shell dissolution mortality occurs for specific size classes of Mercenaria and Mya (2.0 mm). Additional laboratory experiments will determine the immediate response of bivalves to sediment surfaces of different saturation states using a combination of direct observations and flume experiments. The collective results from the field and laboratory will be used to model scenarios of dissolution mortality in both species due to anthropogenic and natural changes in carbonate cycling.Broader impacts of this study include both an extremely strong educational component and important societal benefits. Saint Joseph's College of Maine is an undergraduate institution with about 70% of women in the student body. The immersion of students into research will build on the PI's prior CAREER award and promote students attending and/or presenting research results at national/international conferences contributing as coauthors on manuscripts. Improved understanding of juvenile bivalve mortality could have important impact on management of coastal fisheries. Finally, this research would place coastal populations of juvenile bivalves into context with open ocean plankton with carbonate shells and corals that are currently expected to suffer from similar problems with shell formation and subsequent mortality.