Abstract
Sandy beaches support a wide variety of underappreciated biodiversity that is critical to coastal ecosystems. Prior to the 2010 Deepwater Horizon oil spill, the diversity and function of supratidal beach sediment microbial communities along Gulf of Mexico coastlines were not well understood. As such, it was unclear if microbial community compositional changes would occur following exposure to beached oil, if indigenous communities could biodegrade oil, or how cleanup efforts, such as sand washing and sediment redistribution, would impact microbial ecosystem resiliency. Transects perpendicular to the shoreline were sampled from public beaches on Grand Isle, Louisiana, and Dauphin Island, Alabama, over one year. Prior to oil coming onshore, elevated levels of bacteria associated with fecal contamination were detected (e.g., Enterobacteriales and Campylobacterales). Over time, significant shifts within major phyla were identified (e.g., Proteobacteria, Firmicutes, Actinobacteria) and fecal indicator groups were replaced by taxa affiliated with open-ocean and marine systems (e.g., Oceanospirillales, Rhodospirillales, and Rhodobacterales). These new bacterial groups included putative hydrocarbon degraders, similar to those identified near the oil plume offshore. Shifts in the microbial community composition strongly correlated to more poorly sorted sediment and grain size distributional changes. Natural oceanographic processes could not account for the disrupted sediment, especially from the backshore well above the maximum high-tide levels recorded at these sites. Sand washing and tilling occurred on both open beaches from August through at least December 2010, which were mechanisms that could replace fecal indicator groups with open-ocean groups. Consequently, remediation efforts meant to return beaches to pre-spill compositions caused a regime shift that may have added potential ecosystem function, like hydrocarbon degradation, to the sediment. Future research will need to assess the persistence and impact of the newly formed microbial communities to the overall sandy beach ecosystems.
Highlights
Sandy beaches are highly dynamic coastal buffer zones where the atmosphere, continents, and the oceans interact
Our sampling effort started in early May through early June 2010, before oil came onshore at both beaches based on National Oceanic and Atmospheric Administration (NOAA) Shoreline Cleanup and Assessment Technique (SCAT) maps and reports, available through the Environmental Response Management Application (ERMA) Deepwater Gulf Response web-based GIS tool
Sampling over the winter was not possible because no surface sediment was on the beach at the transect location
Summary
Sandy beaches are highly dynamic coastal buffer zones where the atmosphere, continents, and the oceans interact. A sandy beach includes the geological area parallel to the shoreline that gently slopes from the supratidal, backshore dune with permanent vegetation to the subtidal swash zone at the ocean-water interface, usually at the mean low-tide line, where unconsolidated sediments are deposited and reworked by the highly energetic open ocean [1]. Sandy beaches dominate the world’s open coastlines by covering about 70% of continental shelves [2]. They comprise an important part of any littoral or coastal ecosystem with a wide range of under-appreciated biodiversity [2], and are valued for recreational tourism and fishing economies [3,4]. The microbial diversity and associated processes from supratidal sandy beaches, including dunes, foredunes, exposed open beach slopes, or back-beach berms, have the potential to impact hydrological, sedimentological, and biogeochemical processes that occur throughout the whole beach system
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
