Exploring the impact of historic shipwrecks on microbial biogeography and sediment geochemistry in the deep Gulf of Mexico.

Biological, geological, and artificial features on the deep ocean sea floor alter the contemporary environment and impact microbial community composition and diversity. Historic shipwrecks (> 50 years old) function as habitat features providing food, refuge, and structural basis for benthic biota. Moreover, wooden-hulled shipwrecks can provide organic matter; key resource and form of energy for benthic microbes in deep-sea sediments and important link in the deep-sea biogeochemistry. Therefore, shipwrecks can be considered as islands of biodiversity, shaping microbial biogeography and key ecosystem processes on the seafloor. Gulf of Mexico has more than 2000 historic shipwrecks that pose an unknown impact on the deep-sea environment and sediment microbiome. The goal of this study was to examine the role of two wooden shipwrecks as microbial habitats, their influence on deep-sea biogeography, and determine whether they function as channels for the distribution of deep-sea microbes.The imprint of historic shipwrecks on deep-sea sediment microbial taxonomy was examined using 16S rRNA amplicon sequencing across 3–80 m long lateral transects extending in four directions away from the shipwrecks). Sediment and pore water geochemistry was used to determine environmental changes around the shipwrecks and identify potential drivers of the microbial community structure. Preliminary data show that Shannon diversity was highest in sediments around the shipwrecks and decreased outwards, suggesting that structures on the seafloor are hotspots of microbial diversity. Bray-Curtis similarity analyses showed that the sediment microbiome, geochemistry, and porosity were distinct near the shipwrecks. Changes in microbial diversity and sediment geochemistry were also observed with sediment depth and more pronounced at sites away from the shipwrecks. These results show that artificial structures on the seafloor create an “island effect” and change the deep-sea environment.