According to a new study, there are over three million shipwrecks on seabeds throughout the world, many of which are built of wood, and these sunken wooden islands are proving to be a lively breeding environment for deep sea bacteria.
Scientists say these human-made structures are having an important impact on the delicate ecosystems down at the bottom of the oceans, to an extent that hasn't really been appreciated before.
Because deep sea bacteria living on buried shipwrecks are at the bottom of the undersea food chain, any changes to them might have ramifications for other marine species — and, eventually, anything living on land.
"Microbial communities are important to be aware of and understand because they provide early and clear evidence of how human activities change life in the ocean," says University of Southern Mississippi molecular microbial ecologist Leila Hamdan.
Hamdan and his colleagues chose two 19th-century shipwreck sites in the Gulf of Mexico to investigate. They planted pine and oak blocks around the wreck sites for four months, from very near to the shipwrecks to up to 200 meters (656 feet) away.
Following that, the wooden blocks were collected and tested for bacteria, archaea, and fungus. Microbial diversity increased with distance from the crash sites, peaking at roughly 125 meters (410 feet). The kind of wood also mattered, with oak being better for microbial biodiversity than pine.
Natural hard habitats, such as trees that have fallen into rivers and seas, are already known to have an impact on the biodiversity of the water they fall into. This study demonstrates that human-made shipwrecks have an impact on microbial life beneath the sea.
"These biofilms are ultimately what enable hard habitats to transform into islands of biodiversity," Hamdan explains.
The presence of the shipwrecks boosted microbial richness in the surrounding water and changed the composition and distribution patterns of the biofilms harboring bacteria at both locations, according to the researchers.
Water depth and proximity to other nutrient sources, such as the Mississippi River delta, were other variables impacting microbial life, as predicted.
While further research is needed to look at the phenomena at a wider range of locations, these preliminary findings show that shipwrecks represent a significant factor in underwater biodiversity.
Other human-made structures, such as oil rigs, may have a similar influence on deep sea microbiomes, according to the researchers behind this latest study, and more research is required to find out more.
"While we are aware human impacts on the seabed are increasing through the multiple economic uses, scientific discovery is not keeping pace with how this shapes the biology and chemistry of natural under sea landscapes," Hamdan adds.
"We hope this work will begin a dialogue that leads to research on how built habitats are already changing the deep sea."
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