Award: OCE-1658389

The blue crab (Callinectes sapidus) is an iconic crustacean living in estuaries and coastal marine habitats along the Western Atlantic coast where it serves as a predator, prey and scavenger in benthic marine ecosystems. Blue crabs have a remarkable home-range that extends from Maine to Argentina and supports fisheries and communities throughout. Blue crab is a generalist species with a life historyshaped by the environment and varying with latitude. Variable life history includes the time spent in the plankton as a larva, the location and type of habitat available, phenology of reproduction, and in colder climates it includes winter hibernation or dormancy. Marine organisms are affected by disease across their life history stages and across their geographic ranges, but we know little about how these factors interact to drive disease. We used the Atlantic blue crab and a pathogen, Callinectes sapidus Reo-like Virus 1 (CsRV1), to study how the crab host and disease are connected across their broad range, and how latitude intersects with life history to drive differences in disease. Intellectual Merit We collected blue crab samples across their range for host and pathogen genetics, and to determine patterns in viral prevalence with season and climate. We found that where blue crabs are dormant in the winter, the prevalence of the CsRV1 virus is higher than where they are active year-round such as the tropics. This result could be due to a difference in temperature preference of the virus for cooler warmer waters or lower abundance of blue crabs in the Caribbean that limits transmission of the virus between crabs. Winter sampling revealed lower seasonal prevalence; however, laboratory experiments show that the virus remains present yet scarce in dormant crabs and multiplies rapidly when the water warms. An alternative explanation of lower winter prevalence could be the virus also going dormant and becoming harder to detect. We used population genetics and biophysical modeling to examine transhemispheric blue crab connectivity. Models linked field and laboratory experiments to empirical genetic measurements. Biophysical modeling approaches included a full-decade of larval transport simulations comprehensively throughout the blue crab range and simulations of adult movement, informed by offshore experimental tracking, using the same domain. Our genetic studies show that the blue crab is the same species across its vast range. Further, host genetic differences are significantly related to predicted larval connectivity patterns suggesting that oceanographic processes shape the population. However, the population structure of the pathogen was not significantly related to the predicted structure from models of adult and larval movement. The genetic population of CsRV1 was consistent with the host geographic origins and was only found affecting the blue crab, not any of the other species of Callinectes found within the more tropical portions of the blue crab range. Pairwise distances in CsRV1 genetic relatedness were significantly linked to climate, suggesting that local conditions shape disease in this system. Further, a link was revealed between two geographically distinct CsRV1 populations, putatively through human mediated crab transport among processing facilities. Changes to habitat extent and climate interacted with modeled oceanographic connectivity. Decreased habitat suitability decreased predicted population connectivity through adult movement. This is likely a more realistic model of blue crab dispersal, especially in the tropics where other species of Callinectes may outcompete blue crabs in more saline habitat. However, on the decadal scale of our modeling simulation, larval connectivity still connected the population even as potential links from adult movement decreased. Temperature-based restrictions on spawning and adult movement both decreased crab connectivity in biophysical models. If dormancy decreases while movement rates and spawning periods increase, it is likely that the range of blue crabs, and their pathogen, will continue to expand. Broader Impacts From a fisheries perspective, the tools we have developed can be used for demographic modeling and management, and to predict the spread of blue crabs where they are an emergent invasive species. These data are especially pertinent to commercial sectors and may be of great importance if the expanding blue crab range sustains new fisheries. We worked directly with local fishers, fishery managers, and scientists to collect all of the blue crab samples from across their range. At many of these locations we also gave presentations on the research project and ongoing results. Where appropriate, our partners were engaged in the publication of the results and included as co-authors. A trio of graduate students in the life sciences received formal science communication training alongside museum staff during unique fellowships tailored to each student. The project also involved the training of enumerable graduate and undergraduate students with diverse backgrounds from the University of Florida and University of Maryland. We continue to give presentations stemming from the project to scientific and agency personnel, the latter of whom are using our results in their directives to manage fishery stocks and aquaculture operations. Last Modified: 01/23/2024 Submitted by: AndrewSKough