Fringing salt marshes and submerged aquatic vegetation are critical components of estuarine ecosystems that provide benefits to nekton. Since these two habitats are adjacent, nekton could potentially move interchangeably particularly during tidal ingress/egress. Numerous studies have been conducted in meso- or polyhaline environments where true seagrasses are the dominant type of aquatic vegetation and the faunal community is marine. These studies suggest that salt marshes and seagrasses serve as redundant habitats. However, the roles of aquatic vegetation and fringing marshes at providing habitat benefits are poorly understood in oligohaline environments, particularly in the northern Gulf of Mexico. The overarching goal of this study is to determine the dominant source of basal carbon in west Back Bay of Biloxi using stable isotope analysis. Samples were collected bimonthly from May 2021 to May 2022. Fyke nets and a seine net were used to sample marsh and aquatic vegetative habitats. Faunal samples consisted primarily of small decapod crustaceans and fishes. Vegetation samples were collected haphazardly by hand within each sampling site. In total, 220 individuals spanning 9 species of fishes were analyzed. Including particulate organic matter, epiphytes, and benthic macroalgae, 7 sources of basal carbon were analyzed. Results to date are variable and incomplete, however most consumers appear to be obtaining nutrition from both marsh grasses and aquatic vegetation. Results of this study will improve understanding of the food web in oligohaline environments and could directly inform future restoration efforts as well as fishery management strategies in similar ecosystems.

Coastal ecosystems are undergoing significant changes driven by a range of stressors, many resulting from localized impacts of climate change. Long term environmental changes affect community structure, primarily by shifts in dominant or key species. This study quantified nekton community and species level responses to environmental variation over recent decades. These analyses aim to improve predictions of coastal living resources' response to environmental changes. Trawl sample data from the Alabama Department of Marine Resources Fisheries Assessment and Monitoring Program were used to describe multidecadal patterns in nekton communities across 16 stations in coastal Alabama between 1981 - 2018. Shifts in community structure were assessed through nonmetric multidimensional scaling analysis and post hoc testing. Nekton communities were significantly grouped by station, however there was overlap between stations and a gradient from fresh to saline communities was present. In preliminary analyses, temporal patterns in the multivariate community analysis were convoluted by interacting factors and no significant patterns were identified. Further analyses will assess long-term trends in community structure, and identify relationships between community structure, key species, and key drivers such as freshwater inflow and temperature. This work emphasizes the importance of understanding the relationship between long term environmental changes and biota at a regional scale, and results will be shared with local environmental managers.

Shallow coastal systems act as nursery habitat for many species of fish and macroinvertebrates. Here we assess the use of fringing marsh over adjacent seagrass habitat in the Northern Gulf of Mexico by the juveniles of six widespread species with important commercial, recreational and/or ecological value. We compared monthly paired catches in the fringing marsh and adjacent seagrass bed in three sites along coastal Alabama over two years. Our results reveal a rather consistent species ranking across sites where use of fringing marsh over adjacent seagrass beds is lowest for pinfish and spotted sea trout, intermediate for American silver perch and brown shrimp, and highest for blue crab and white shrimp. Despite this consistent ranking, the extent of the differences in use of fringing marsh over adjacent seagrass among these three groups varied largely across sites. The results suggest some species make higher use of fringing marshes as juvenile habitat than do other species, and that such differences, while being similar in direction, are more pronounced in some sites. We also found potential evidence that, for the three species of macroinvertebrates, juveniles that use the fringing marsh are larger on average than those that do not, but confirming this requires more work. This study improves our understanding of the dependence of fish and macroinvertebrates on shallow coastal systems as recruitment grounds. Furthermore, we base our results on a habitat use metric that is robust to gear performance differences among the habitats compared, and thus offers promise for application elsewhere.