| Oil spills can cause deleterious impacts to many coastal organisms, including microalgae. Many microalgae thrive as epiphytes living on macroalgae or seagrass hosts. These epiphytic algae make up part of the microbiome that also includes associated micro- and mesograzers and have a great influence on the surrounding micro-benthic community as well as the overall ecosystem. It is important to understand how these communities are impacted because they can be used as indicators of ecosystem health and resilience, as well as potential biomarkers of oil pollution. There is little research, however, on how oil impacts epiphytic communities. The objective of this study was to determine how the community composition of epiphytic microalgae changes due to the influence of natural crude oil exposure. The potential influence of oil exposure was tested by examining 48 epiphyte samples collected from the Chandeleur Islands (Louisiana) in September 2015 and 2016, at sites with exposure to low, moderate, and high levels of oil during the Macondo oil spill. The community composition was identified to the lowest taxonomic units possible, and quantified. The relative abundance, cell size, and biodiversity per composite sample of microalgae were compared against host species distinctions, oil exposure, date and sites through ANOSIM and SIMPER analyses in PRIMER. The data presented suggest that the lingering impact of oil on epiphyte communities persists 5--6 years after the spill. Ecosystem services, however, do not appear to have been altered according to proxy biodiversity comparisons. Diatoms dominated at all sites for all years, similar to baseline compositions. Greater similarity (i.e., stability) was seen between sites with less initial oiling. Overall, these data suggest there are lingering impacts from the oil spill, but the ecological change in community structure is minimal. Due to the lack of existing data on the impacts of oil exposure on these communities, this study provides baseline research for future studies. |
