Site Characteristics More Than Vegetation Type Influence Food Web Structure of Intertidal Salt Marshes

Salt marshes are under increasing anthropogenic pressures that have been reported to affect the diet of fish (e.g., change in prey composition and availability), eventually resulting alterations their nursery function. Most studies Europe based on gut content analysis, which only reflect a small proportion salt marshes, do not necessarily long-term disturbances. In this study, we investigated impact salt-marsh vegetation type trophic network structures (i.e., position). Primary producers (particulate organic matter, microphytobenthos, dominant terrestrial plants), potential aquatic prey, two species (sea bass thinlip mullet) were sampled during summer 2010 four creeks from sites Western France (the Mont-Saint-Michel Bay Seine Estuary). Analysis was undertaken using C N stable-isotope compositions. Tested response variables (diet position) suggested site effect weaker surrounding type. Site attributed differences nitrogen inputs (with steep increase Bay) tidal regime between bays, with more marine signatures associated higher frequency duration flooding events Estuary. A second hypothesis is invasive Elytrigia acuta , has recently replaced typical Bay, negatively impacted native salt-marshes function by modifying access site. The position sea mullet unchanged local vegetation, considered consistent diet. This study highlights relevance stable-isotopes analyses for assessing integrative effects changes human disturbances marshes.