In the northern Gulf of Mexico (GOM) the blue crab (Callinectes sapidus) is a keystone species in salt marshes and supports a $50M/yr. fishery. Populations of blue crabs depend on recruitment of larvae that are spawned offshore where they are planktonic for a month or two before returning to coastal waters and metamorphosing into juvenile crabs. It is not known how far blue crab larvae are typically carried by currents, so the extent to which populations are selfsustaining versus dependent on other sources of larvae is also unknown. Although the effects of the Deepwater Horizon spill (DWH spill) on blue crabs have yet to be determined, the spill coincided with the critical period during which larvae were developing in the plankton, and larvae collected during the spill were found to have abnormal oily deposits under their carapaces.
My lab was actively investigating blue crabs along the coast of Louisiana at the time of the spill. Our research was addressing the extent to which the dispersal of larvae connects populations and whether individual populations have become adapted to their local environments. These questions are generally regarded as crucial in the design of marine protected areas, fisheries management and the science of ecosystem recovery (COWEN et al. 2006; HAUSER and CARVALHO 2008). Our approach is based on state-of-the art methods that use single nucleotide polymorphisms (SNPs) in DNA sequences to estimate dispersal (BEERLI and FELSENSTEIN 2001; FALUSH et al. 2003) and to identify genes involved in local adaptation (NARUM and HESS 2011).