Abstract
Crude oil contains many different compounds that can alter various components of marine ecosystems (e.g. benthic food webs), including the microphytobenthos (MPB). As the impacts of crude oil exposure on MPB community dynamics are poorly known, the purpose of this study was to compare subtidal MPB community responses (i.e. changes in biodiversity, resilience, and recovery) of a previously-exposed population (Chandeleur Islands, Louisiana), to a naïve population (Estero Bay, Florida) in controlled laboratory microcosm experiments (6.5 cm diameter sediment cores). We hypothesized that some communities of MPB will be hindered by the crude oil and its components, while others may be stimulated; there may also be a shift in community structure and composition between the MPB communities. Eighteen sediment cores (9 from each study site) with three different treatments of water-accommodated fraction (WAF) of crude oil (100%, 50%, and 0% WAF) were sampled over an 18-week period. During the exposure period, the 100% WAF cores were re-oiled for the full 7 days, while the 50% WAF cores were subjected to a decreasing exposure of WAF by 50% each day to simulate an oil spill and subsequent dilution. Samples were collected over the course of the experiment for microscopy counts for community composition. Additionally, in-situ measurements of photosynthetic optimum yield and total maximum fluorescence were taken. The results of this study indicate that the MPB community structure and composition of the Chandeleur Islands, LA and Estero Bay, FL were altered due to oil exposure, although only to a certain extent detectable by the measurements used in this study. Successional processes were also identified by several analyses of the abundances from the treatments from both study sites. There was also evidence of potential resiliency and/or recovery within the Chandeleur Island and Estero Bay communities, although daily fluctuations in MPB inhibition and stimulation also seemed to occur.The results of this study indicate that the MPB community structure and composition of the Chandeleur Islands, LA and Estero Bay, FL were altered due to oil exposure, although only to a certain extent detectable by the measurements used in this study. Successional processes were also identified by several analyses of the abundances from the treatments from both study sites. There was also evidence of potential resiliency and/or recovery within the Chandeleur Island and Estero Bay communities, although daily fluctuations in MPB inhibition and stimulation also seemed to occur.