Fish and invertebrate community structure and food-web dynamics in tidal creeks in an anthropogenically fragmented, coastal landscape


The purpose of the proposed work is to use multiple SIA to quantify the food webs in fragmented, partially fragmented, and natural, intact salt marsh tidal creeks in the Pascagoula River estuary in a three-tiered methodology.


First, geo-referenced, satellite imagery and geo-statistical analysis using GIS software will be used to assess the degree of anthropogenic fragmentation in the PRE and identify 2 replicates for each of the three creek types.  Second, primary producers, benthic invertebrates, and nekton will be collected from each of the replicate creek types in order to identify assemblage differences.  Lastly, carbon (δ13C), nitrogen (δ15N), and sulphur (δ34S) will be used to quantify food web dynamics among four different trophic groups: 1) primary producers (10 emergent & submerged species); 2) the 5 most abundant infaunal invertebrates (i.e., organisms that live within the sediments); 3) the 5 most abundant epifaunal invertebrates (i.e., organisms that live at the sediment-water interface); and 4) the 5 most abundant nekton.  SIA is now recognized as a preferred technique for trophic studies, and offers distinct advantages over traditional diet analysis in that it is a time-integrated measure of the materials assimilated by nekton through their diets, can be used to identify the primary carbon sources in a food web (δ13C and δ34S), and can also be used reconstruct trophic pathways from primary producers to upper level consumers (δ15N).


The research outlined would be a cutting edge extension and enhancement of the research occurring in my lab for the last decade on alteration of salt marsh environments and the impacts to ecosystem sustainability.  It would also be a portion of my PhD student’s dissertation project and enhance his work as well.  The total cost to do all samples is $12,375 if we send our SIA samples to other facilities.  However, if we do all analyses in the new Isotope Facility at the MERL Building on our Cedar Pt Campus, costs will be markedly less and we will be able to get more samples processed for much less cost.  It will also support the new and specialized USM facility here on the coast and provide valuable training and experience for my PhD student on state-of-the-art equipment.  Overall, support for this project will enhance research in my lab and at USM because we are doing applied science which has great social benefit in the coastal zone. The Gulf coast of Mississippi is undergoing rapid development that impacts salt marsh ecosystems which provide nursery areas for commercially, recreationally and ecologically important fisheries species.