Abstract:

Seagrasses and salt-marshes provide critical habitat for ecologically and economically important finfish and shellfish; exhibit exceptionally high rates of primary production; sequester significant amounts of carbon through photosynthesis; filter runoff; and stabilize sediments in shallow coastal waters. Seagrass and salt - marsh habitats, therefore, represent some of the most valuable, but at the same time the most vulnerable, ecosystems on earth owing to their position at the receiving end of riverine systems, their proximity to large population centers and the threat of sea level rise. An additional, more immediate threat to these habitats was the 2010 Deepwater Horizon oil spill. The direct and indirect ecological effects of the Deepwater Horizon event may have long-term impacts on coastal vegetated habitats, in terms of flora and fauna composition and abundance, but are contingent on the amount and type of oil they received, as well as the duration of exposure. Data available from NOAA observers indicate there was an east-west gradient in exposure, with the greatest amounts of oiling in Louisiana and only light, sporadic oiling from Mississippi Sound east to northwest Florida. Based on the lack of oiling along the seagrass and marsh habitats of Mississippi, Alabama and Florida, focus was directed to the Chandeleur Island chain in eastern Louisiana where oiling occurred at both high and low levels. Additionally, during the past several years we have gathered quantitative data on the composition and biomass of seagrass and marsh flora and their associated mobile macroinvertebrates and juvenile fishes from a number of locations along the north-central Gulf Coast stretching from the Chandeleur Islands in Louisiana to St. Joe Bay, Florida, thus we have a considerable baseline data with which to compare future habitat changes with. These important baseline data allow for the implementation of a Before-After, Control-Impact (BACI) assessment of oil-related impacts. By combing pre-spill baseline data, data from a complementary project within oil-free sites in Alabama, and data collected as part of this project, we examined whether there are long-term effects (>1 year post-spill) from the Deepwater Horizon event on the structure and function of salt-marsh, mangrove and seagrass floral communities and their associated faunal assemblages. Comprehensive study effects of oil spill on habitats of seagrass/marsh dominated by Spartina alterniflora/black mangrove/mix marsh-mangrove in the Chandeleur Islands along a high to low oiling gradient.