Abstract:

These data are the result of a synthesis of published literature. A workshop was convened in October 2015 with the goal of identifying key species in the response of marsh food webs to oil. The majority of the literature review was conducted at this workshop, and was continued into early 2016 (completed by March 2016). Our synthesis consisted of literature reviews focusing on: 1) studies of trophic relationships of marsh organisms, and 2) studies of oil sensitivity of marsh organisms. This synthesis allowed us to build a food web model of a Louisiana salt marsh and quantify the topological importance of each taxon in that web. We then combined information of food web importance and sensitivity to oil to identify the taxa that are critical for the response of the overall food web to oil.

Suggested Citation:

Michael J. McCann, Kenneth W. Able, Robert R. Christian, F. Joel Fodrie, Olaf P. Jensen, Jessica J. Johnson, Paola C. López-Duarte, Charles W. Martin, Jill A. Olin, Michael J. Polito, Brian J. Roberts, Shelby L. Ziegler. 2016. Identifying key species in marsh food web responses to The Deepwater Horizon Oil Spill: A literature review. Distributed by: Gulf of Mexico Research Initiative Information and Data Cooperative (GRIIDC), Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/N7RN35V6

Publications:

McCann, M. J., Able, K. W., Christian, R. R., Fodrie, F. J., Jensen, O. P., Johnson, J. J., … Ziegler, S. L. (2017). Key taxa in food web responses to stressors: the Deepwater Horizon oil spill. Frontiers in Ecology and the Environment. doi:10.1002/fee.1474

Purpose:

Based on the available literature, building a salt marsh food web (binary presence or absence of feed links) and quantifying the sensitivity of marsh taxa to oil spills.

Data Parameters and Units:

• Food web links (list of each consumer-resource interactions between marsh taxa and the references used to support them) • Food web diet matrix (matrix of 0s or 1s indicating the presence/absence of trophic interactions) • Oil sensitivity scores (ratings of oil sensitivity for taxa in the food web and the references used to support them) In-Degree: The number of edges going into a node. Equal to the number of prey items that a node feeds on. Generalist consumers will have a higher in-degree than specialists. For the lowest trophic levels in our food web, in-degree will be 0, since they have no resources. Out-Degree: The number of edges going out of a node. Equal to the number of predators that feed on a node. Nodes at higher trophic levels may be expected to have a lower out-degree, since they have fewer predators. Higher out-degree suggests that more consumers use taxa that taxa as a resource. Betweenness: The number of shortest paths from all nodes to all others that pass through a node. Betweenness will typically be higher for nodes at intermediate trophic levels. Regular equivalence: Two nodes are regularly equivalent if they interact with nodes with similar network positions (but not necessarily the same nodes). The sum of all regular equivalence values between a focal node and all other nodes in the network quantifies the uniqueness of that node in the network (Lai et al. 2012). Importance: The four network indices (ie in-degree, out-degree, betweenness, and sum of regular equivalences) were scaled as a z-score (by subtracting the mean and dividing by the standard deviation). To combine the four indices into one, the scaled values were averaged to determine a single food web importance score for each node.

Methods:

Literature Review

Individual Files: