Abstract
More than 2,000 historic shipwrecks spanning 500 years of history, rest on the Gulf of Mexico seafloor. Shipwrecks serve as artificial reefs and hotspots of biodiversity by providing hard substrate, something rare in deep ocean regions. The Deepwater Horizon (DWH) spill discharged crude oil into the deep Gulf. Because of physical, biological, and chemical interactions, DWH oil was deposited on the seafloor, where historic shipwrecks are present. This study examined sediment microbiomes at seven historic shipwrecks. Steel-hulled, World War II-era shipwrecks and wooden-hulled, 19th century shipwrecks within and outside of the surface oiled area and subsurface plume were examined. Analysis of 16S rRNA sequence libraries, sediment radiocarbon age data, sedimentation rates, and hydrocarbons revealed that the German U-boat U-166 and the wooden-hulled sailing vessel known as the Mardi Gras Wreck, both in the Mississippi Canyon leasing area, were exposed to deposited oil during a rapid sedimentation event. Impacts to shipwreck microbiomes included a significant increase in Piscirickettsiaceae-related sequences in surface sediments, and reduced biodiversity relative to unimpacted sites. This study is the first to address the impact of the spill on shipwreck-associated microbiomes, and to explore how shipwrecks themselves influence microbiome diversity in the deep sea.
Highlights
The Deepwater Horizon (DWH) spill of 2010 resulted in an uncontrolled release of 5 million barrels of oil[1]
Sites were selected from the Bureau of Ocean Energy Management (BOEM) and Bureau of Safety and Environmental Enforcement (BSEE) shared shipwreck database[13,14]
Data for hopanes, the 50 most abundant polycyclic aromatic hydrocarbons (PAHs), and dioctyl sodium sulfosuccinate (DOSS) from the Natural Resource Damage Assessment (NRDA) dataset from the study areas underscores the differences between sites (Fig. 1)
Summary
The Deepwater Horizon (DWH) spill of 2010 resulted in an uncontrolled release of 5 million barrels of oil[1]. Within the footprint[6] is an area extending ~16 km southwest of the Macondo well described as having an “acute footprint” from the spill In this area, where sediment hopane concentrations indicative of DWH oil deposits exceed 800 ng g−1 1,6, are three historic shipwrecks (Fig. 1)[10]. The shipwrecks are the steel-hulled, German U-boat U-166 and two wooden-hulled, 19th century shipwrecks known as the Mica Wreck and the Mardi Gras Wreck The proximity of these shipwrecks to the Macondo well, and location within the DWH spill footprint, raises questions about the spill’s impact on biota on and surrounding these artificial reefs, and the physical integrity of the shipwrecks
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