Collaborative Research - Connectivity of Bivalve Populations: Assessing Sources of Larval Recruits

大多数海洋底栖无脊椎动物的早期生活史涉及浮游幼虫的发育阶段，这一阶段是固着或久居的成年种群之间增加扩散和基因流动的媒介。关于人口之间联系的空间规模和强度，仍然存在相当大的争论。这项研究项目将研究双壳类种群的连通性(定义为当地种群从外部来源接收新兵的程度)、物理运输的作用以及集合种群的后果。因为幼虫阶段是微小的，所以几乎不可能跟踪个体，或者用传统的标签追踪它们。技术进步促进了利用微量元素分析来评估一些浮游幼虫的来源和轨迹。生物成因碳酸盐的地球化学记录了不同海岸水团的环境和痕量元素特征的空间变异性。由于贝壳在浮游幼虫的整个发育过程中都有沉积，它们有效地记录了幼虫在发育过程中所占据的不同栖息地的环境特征的变化。对新安置的双壳类保留的幼虫壳进行分析，将提供有关其来源位置的信息。将使用微量元素指纹方法来评估马萨诸塞州和南加州海岸双壳类种群之间的联系的空间规模和强度。假说将涉及(1)远地幼虫来源相对于本地幼虫来源(自播)的相对贡献，(2)循环驱动的扩散潜力与双壳类种群之间实现的连通性之间的关系，以及(3)物种产卵期、浮游期和地点的空间分离在决定幼虫交换概率方面的作用。我们的方法包括激光消融电感耦合等离子体质谱(LA-ICPMS)来解决幼虫外壳组成的空间变化，这些变化反映了幼虫的招募来源和运输的时间模式。我们将研究新英格兰的贻贝Mya arenaria和贻贝Mytilus edulis，以及加利福尼亚州南部的贻贝Mytilus galloapcialis和M.calfornianus。种群连接性将用两种集合种群方法来研究，这两种方法从流体动力学模型估计扩散概率。一个涉及栖息地面积作为繁殖力的代理，另一个是多区域矩阵模型，使用人口统计框架来描述集合种群的动态。我们将根据循环和集合种群模型的先验预测，测试通过对招募来源的痕量元素分析确定的已实现的种群连通性。广泛的影响：由此产生的关于源种群和连接性的信息将增强对具有商业价值的双壳类物种集合种群动态的理解。适用于美国东海岸和西海岸的连通性信息将通过改进海洋保护区和渔业条例的设计，促进沿海资源的养护。主要的教育内容包括本科生、研究生和博士后，以及早期职业科学家，参与整合沿海海洋物理学、幼虫生态学和集合种群理论的跨学科研究。将把微量元素指纹技术(从鱼类)转移到无脊椎动物扩散领域和墨西哥的合作者。

The early life history of most marine benthic invertebrate organisms involves a planktonic larval stage of development that acts as an agent for increased dispersal and gene flow between sessile or sedentary adult populations. There remains considerable debate as to the spatial scale and strength of the connections between populations. This research project will examine connectivity of bivalve populations (defined as the extent to which a local population receives recruits from external sources), the role of physical transport, and the metapopulation consequences. Because larval stages are microscopic, it is all but impossible to follow individuals, or to track them with conventional tags. Technological advances have facilitated the use of trace element analysis to evaluate origins and trajectories of some planktonic larvae. Spatial variability in environmental, trace elemental characteristics of different coastal water masses is recorded in the geochemistry of biogenic carbonates. Because shells are deposited throughout planktonic larval development, they effectively record changes in environmental characteristics of different habitats occupied by larvae through development. Analysis of larval shell retained by newly settled bivalves will provide information about their source locations. Trace element fingerprinting methods will be used to evaluate the spatial scale and strength of connectivity among bivalve populations on the Massachusetts and southern California coasts. Hypotheses will address (1) the relative contribution of remote larval sources versus local ones (self seeding), (2) the relationship between circulation?driven dispersal potential and realized connectivity among bivalve populations and (3) the roles of species spawning period, planktonic period, and spatial separation of sites in determining probabilities of larval exchange. Our approach involves laser ablation inductively coupled plasma mass spectrometry (LA?ICPMS) to resolve spatial changes in larval shell composition that reflect recruit origins and temporal patterns of larval transport. We will work with the clam Mya arenaria and the mussel Mytilus edulis in New England and the mussels Mytilus galloprovincialis and M. californianus in southern California. Population connectivities will be studied with two metapopulation approaches that estimate dispersal probabilities from hydrodynamic models. One involves habitat area as a proxy for fecundity and the other is a multiregional matrix model that uses a demographic framework to describe the dynamics of the metapopulation. We will test realized population connectivity determined from trace elemental analysis of recruit origins against a priori predictions based on the circulation and metapopulation models.Broader impacts: The resulting information about source populations and connectivities will enhance understanding of metapopulation dynamics in commercially valuable bivalve species. Connectivity information applicable to the east and west coasts of the USA will facilitate conservation of coastal resources through the improved design of marine protected areas and fisheries regulations. Key educational elements include the involvement of undergraduate, graduate, and postdoctoral students, as well as early career scientists, in interdisciplinary research that integrates coastal ocean physics, larval ecology and metapopulation theory. There will be a transfer of trace element fingerprinting technology (from fish) into the realm of invertebrate dispersal and to collaborators in Mexico.[edited - JP - 7/7/03]