Identifying key species for food web responses to anthropogenic stressors relies on quantifying both the sensitivity of individual taxa and their importance in the overall web of species interactions. Occurrence of especially sensitive species in key network positions should decrease ecosystem resistance (i.e., stability) to human perturbations. Despite widespread concern for coastal environments after the 2010 Deepwater Horizon Oil Spill in the Gulf of Mexico, few studies have assessed impacts on the overall marsh food web. Here, we synthesize published studies on trophic relationships and oil sensitivity to identify critical species in the response of the marsh food web to oil.
Our marsh food web network model consists of over 50 nodes (i.e. trophic species) and more than 375 binary feeding links. Organisms that we expect to be critically sensitive because of their high food web importance and high sensitivity to oil include gulls and terns, omnivorous snails, and all marsh plants. Taxa that should be critical to enhancing the stability of the food web because of their high food web importance and low sensitivity include carnivorous fish living on the marsh (e.g., Fundulus) and large, carnivorous fish living off the marsh surface (e.g., red drum, spotted gar). Our work has also identified information gaps that limit our ability to predict effects of future oil spills or other stressors on this ecologically and economically important ecosystem. Regardless of the threat, organisms with high food web importance should be a conservation priority because of the potential for indirect, negative effects on the rest of the ecosystem.