Much uncertainty exists regarding the impact that oiling may have on the ecology of intertidal salt marsh systems. The Deepwater Horizon event provides a unique opportunity to assess the manner in which salt marsh communities respond to stressors of this nature. In addition, it provides an opportunity to evaluate the long-term response of the salt marsh community at several levels.
In this work, we are investigating the impact of exposure to oil and dispersants from the Deepwater Horizon spill on intertidal salt marsh communities in Alabama and Louisiana. Information from the National Oceanographic and Atmospheric Administration SCAT-Mobile Ground Observations after the spill indicated impacted areas on Point aux Pins, near Bayou La Batre on Mississippi Sound in coastal Alabama. Ecologically similar areas on the western side of the point were not indicated to be impacted. Similar NOAA data for coastal Louisiana indicated oil-impacted areas in Timbalier Bay near Port Fourchon, LA, with ecologically similar but unoiled areas located nearby.
In January of 2010, we began a monthly sampling program at the impacted and unimpacted sites at the Point aux Pins (Alabama) site.
Monthly collections include:
Macrofaunal collections made in two tidally flooded weirs at each site in which screens are dropped at high tide and collections made from sunken catch boxes at low tide
Replicate meiofaunal samples at each site taken by coring tube and sectioned into 2 mm intervals
Enumeration of microbial communities (collected in coordination with meiofauna) samples by epiflourescence microscopy
Assessing macrophyte above- and belowground productivity.
In March of 2010, we initiated a similar sampling program at the Louisiana site. Louisiana collections duplicate those in Alabama with the exception that the no macrofaunal samples are collected and that Louisiana sampling is done quarterly rather than monthly. In an attempt to verify that the oiled and unoiled sites at both locations do in fact differ in the degree of oil exposure, sediment samples were provided to colleagues in the Department of Physical Sciences at The University of West Alabama with the goal of identifying a signature for the BP oil and assessing the magnitude of impact at each site.
Although data collection and analysis is in the very early stages, preliminary results have been obtained for some analyses. In Alabama meiofaunal samples, nematode densities are significantly higher at the unoiled (western) location than at the oiled site on the eastern side of Point aux Pins. Furthermore, initial aboveground plant biomass and height is greater in unoiled sampling areas when compared to those that received oiling.