Project: Larval orientation, dispersal and connectivity in a brachyuran crab under ocean acidification and elevated temperature

NSF Award Abstract:
The stone crab fishery is a multimillion-dollar commercial industry in Florida, which may not be sustainable given forecasted climate change and the predicted increases in extreme weather events. Stone crab larval swimming behavior and survivorship are negatively affected by reduced pH (ocean acidification) and elevated temperatures. These conditions are expected to become more common and widespread along the western Florida coast and may impact the supply of larvae that settle into and replenish both unfished and fished populations. Changes in larval dispersal could lead to recruitment failure; however, the extent of such an outcome is currently unknown. The goal of this study is to develop models that forecast the abundance and distribution of Florida’s stone crabs under future climate scenarios. Laboratory experiments are quantifying how temperature and pH affect larval survivorship and behavior. Results from the laboratory studies are being integrated with information on ocean currents and chemistry into a biophysical model. This model predicts the effects of climate change on the stone crab population by combining projections of the physical and chemical environment with climate-induced changes to larval behavior. The broader impacts include relevance to sustainable management of the stone crab and other coastal crustacean fisheries, training opportunities for undergraduate and graduate students, and educational outreach. Curriculum development is occurring in partnership with Title-1 schools, and high-school students are developing short documentaries to be entered into a marine science film festival at Florida Southern College.

In many coastal habitats, ocean acidification (OA) is occurring at an accelerated rate relative to end-of-century projections, largely due to localized wetland degradation, increased runoff, and eutrophication, all of which amplify variability in coastal pH. The ability to project future persistence of marine species and the sustainability of coastal fisheries depends on understanding how the combined effects of acidification and elevated temperature impact population connectivity and recruitment. Even small changes in planktonic larval survivorship, behaviors, or dispersal can lead to large population changes; however, predicting these changes requires understanding the biology of the organisms within the context of how the physical and chemical environment is changing. When exposed to reduced pH and elevated temperature conditions similar to those expected at the end of the century, some larvae not only experience increases in mortality, but they also change their swimming behavior, which in turn alters their dispersal in the coastal ocean. This study is quantifying the combined impacts of OA and elevated temperature on the dispersal and connectivity of a brachyuran crustacean, the stone crab. Controlled laboratory studies are measuring the effects of changes in pH and temperature on larval vertical swimming behavior, development, and survivorship. The results from the laboratory studies are being integrated with high-resolution spatially and temporally realistic hydrodynamic and carbonate chemistry projections in a coupled biophysical model to predict modifications to larval dispersal and their impact on population connectivity and persistence under different environmental conditions. This study is providing new insights into how larval behaviors affect the resilience of a crustacean metapopulation by quantifying dispersal patterns and connectivity, potential population fragmentation, and overall recruitment under current and future climate scenarios.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria. ​This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).