(ORDO NEWS) — There are an estimated three million shipwrecks on the seafloor around the world, many of which are made of wood, and these submerged wooden islands are a breeding ground for deep-sea microbes, a new study has found.
Scientists say these man-made structures are having an important impact on the fragile ecosystems at the bottom of the oceans, to a degree that has not yet been fully appreciated.
Deep-sea microbes that live on sunken ships are at the bottom of the underwater food chain, so their changes could affect other marine life – and ultimately all life on land.
“Microbial communities are important to know and understand because they provide early and clear evidence of how human activity is changing life in the ocean,” says molecular microbial ecologist Leila Hamdan of the University of Southern Mississippi.
Hamdan and other researchers chose two 19th-century shipwrecks in the Gulf of Mexico for their study. They placed pine and oak blocks around the shipwrecks, from their immediate vicinity to a distance of 200 meters (656 feet), and left the timber for four months.
The wooden blocks were then removed and measured for bacteria, archaea and fungi. Microbial diversity varied with proximity to shipwrecks, peaking at around 125 meters (410 ft). The type of wood also mattered, with oak being more favorable to microbial biodiversity than pine.
Natural hard habitats – trees that have fallen into rivers and oceans – are already well known for affecting the biodiversity of the waters they fall into. This study shows that shipwrecks left behind by humans also affect microbial life underwater.
“These biofilms are what ultimately allow hard habitats to develop into pockets of biodiversity,” says Hamdan.
Overall, at the two sites, the presence of the wrecks increased the microbial richness in the surrounding water and also altered the composition and dispersion patterns of microbial-trapping biofilms, the researchers found.
As expected, water depth and proximity to other nutrient sources such as the Mississippi River Delta were additional factors affecting microbial life.
While further research is needed to examine this phenomenon across a wider range of sites, these first results are sufficient to show that shipwrecks are an important contributor to underwater biodiversity.
The latest study’s team of authors suggests that other man-made structures, such as oil rigs, may have similar effects on deep sea microbiomes, and further research is warranted to try and elucidate the details.
“While we know that human impact on the seafloor is increasing through multiple economic uses, scientific discoveries have not kept pace with how this affects the biology and chemistry of natural underwater landscapes,” says Hamdan.
“We hope this work will spark a dialogue that will lead to exploration of how built habitats are already changing the deep sea.”
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