Award: OCE-1155609

Project Outcomes Report for NSF/Bio/Oce 1155609 Title: Collaborative Research: Interacting effects of local demography and larval connectivity on estuarine metapopulation dynamics A fundamental issue concerning the population dynamics of marine organisms and marine conservation biology involves identifying the paths of larval dispersal connecting isolated populations, and how variation in intensity of dispersal along these paths influences the how these populations fluctuate in space and time. These isolated populations often form what is referred to as a "metapopulation", which can sometimes contain "source" populations whose birth rates are greater than death rates, therefore providing offspring to other populations via dispersal of larvae or adults. Conversely, isolated "sink" populations are those whose death rates are greater than birth rates, such that their persistence is dependent upon source populations. Marine protected areas can potentially subsidize harvested populations via larval spillover, however, spillover benefits can only be realized if harvested areas contain suitable habitat for larval settlement and survival. This study used the eastern oyster (Crassostrea virginica) in Pamlico Sound (PS), North Carolina (NC), USA as the model system to understand how the interacting effects of resource management (e.g., no-take sanctuaries vs fished areas), local oyster demography (e.g., births & deaths), and oyster larval connectivity influenced the dynamics and restoration potential of one of the most important ecosystem engineers in estuarine systems, and whose abundance is at historic lows globally. Intellectual Merit: The results confirm the benefits of reef restoration and no-take sanctuaries. Not only were oyster densities up to 72 times higher in the no-take sanctuaries than harvested reefs, but few oysters in harvested reefs were greater than the legal harvesting size, whereas protected reefs typically had oysters of different sizes, including many large individuals. Furthermore, the potential larval output was around 6 times higher in the restored, protected reefs. This suggests that there is more larval spillover from sanctuaries to harvested reefs than the other way around – sanctuaries can contribute substantially to the larval supply of the oyster metapopulation. The field observations of oyster demographic rates were then integrated into a metapopulation modeling framework to simulate the entire oyster metapopulation to understand underlying source-sink dynamics. We found that larval connectivity among oyster populations, which is driven mainly by wind-driven surface currents, is a major determinant of the dynamics of the overall metapopulation, followed in importance by reef-specific population sizes, demographic rates, and location of a population within Pamlico Sound. Similar to field observations, the metapopulation model found that 86% of the no-take oyster sanctuaries served as metapopulation sources. Broader Implications: Future management efforts should consider oysters as an interconnected metapopulation, with continued efforts to protect and restore frequent ?source? subpopulations while managing harvest from ?sink? subpopulations. An important outcome from this work was the development and application of GIS-based decision support tools that have been adopted at state (NC Division of Marine Fisheries) and national levels (NOAA, The Nature Conservancy) to help guide oyster conservation and restoration, as well as aquaculture. The study supported the training of 3 PhD students, 3 MS students, and 8 undergraduate students. Last Modified: 06/13/2018 Submitted by: David B Eggleston