Dynamics of regime shifts in diverse and spatially structured marine communities

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My proposed research is on the dynamics of regime shifts in complex spatially structured marine communities. Regime shifts are nonlinear, typically rapid, changes in an ecological state. Regime shifts in natural systems involve many different species whose abundances can change at very different rates, and can play out across large spatial scales. My program will focus on developing new approaches to understanding the dynamics of regime shifts in spatially and size-structured food-webs, using the collapse of the groundfish populations in the Northwest Atlantic benthic food web as a focal case. We will develop statistical approaches to model the spatiotemporal dynamics of communities during regime shifts and community-level theoretical models of large-scale marine systems to evaluate different potential causes of the Northwest Atlantic regime shift. Our first objective will be to develop statistical tools to detect shifts in complex and spatially structured communities. My group will test and extend a statistical method I developed to detect shifts in spatially structured communities, and will use simulations and long-term data from the Northwest Atlantic to test how effective it is for detecting shifts. We will extend the model to include phylogenetic relatedness and functional trait data to better understand what components of a given community are involved in a shift. The second objective will be to develop spatially structured size-spectrum models to evaluate potential causes of the groundfish collapse, and test the effectiveness of community-level and spatial predictors for forecasting regime shifts in marine systems. We will develop a metacommunity size-spectrum model of the Newfoundland and Labrador Shelf, incorporating size-specific demographic and dispersal rates. We will use these models to test whether different hypothesized drivers of the groundfish collapse are able to generate the observed patterns of collapse and recovery in this ecosystem. Our third objective will be to develop theory on the effects of interacting patterns of movement of fish and human harvesters on the resilience of fisheries to regime shifts. We will use long-term records from vessel monitoring systems to estimate movement models for fishermen's responses to changing fishing conditions, and use these results to extend my prior theory of the effects of interspecific variability in dispersal into a broader theory of how varying patterns of non-adaptive or adaptive movement at different trophic levels change how susceptible fished ecosystems are to regime change. This research will inform decisions on how to effectively manage fisheries in this region, and the statistical and theoretical techniques developed will contribute more broadly to research into the dynamics of species abundances and distributions in complex spatially structured trophic communities.