Cooperative Fish and Wildlife Research Units Program: Louisiana
Education, Research and Technical Assistance for Managing Our Natural Resources

DeMarco, K, E. Hillmann, M. Brasher, M. La Peyre. 2016. Brackish marsh zones as a waterfowl habitat resource in submerged aquatic vegetation beds in the northern Gulf of Mexico. Journal of the Southeastern Association of Fish and Wildlife Agencies 3:261-269.


Submerged aquatic vegetation (SAV) beds are prevalent in shallow coastal habitats that are increasingly exposed to sea-level rise (SLR) effects. In the northern Gulf of Mexico (nGoM), an area particularly vulnerable to SLR, the abundance and distribution of SAV food resources (seeds, rhizomes and tissue) can influence the carrying capacity of coastal marshes for waterfowl. Despite the documented importance of SAV within coastal ecosystems, and specifically to waterfowl, little is known about their distribution across coastal landscapes and salinity zones, or the potential impacts of SLR. We estimated SAV cover and seed biomass in coastal marshes from Texas to Alabama in summer 2013 to assess variation in SAV and seed resource distribution and abundance across the coastal salinity gradient. Coast-wide, SAV percent cover was similar between all salinity zones (10-20%) however patterns of distribution differed between salinity zones. Specifically, saline sites were characterized by fewer sites with SAV, but sites with SAV had greater percent cover as compared to fresh, intermediate and brackish zones. Coast-wide means for seed biomass were highly variable, and not significantly different across salinity zones although waterfowl forage availability was lowest in saline zones (<0.5 g m-2) as compared to fresh, intermediate and brackish zones (>1.2 g m-2). As local SLR models predict altered coastal marsh types are likely along the nGoM, these findings suggest concurrent changes in spatial distribution and abundance of SAV and seed resources. If trends identified here are persistent across the coast, SAV resources available for waterfowl may be similar among fresh, intermediate and brackish marsh types.