March 28, 2024

Shipwrecks: Life After the Sinking

Shipwrecks: Life After the Sinking

Thus, in small boarding crews, not only destructive forces act. After all, microbes not only break down iron, but also promote a whole host of other chemical processes. For example, they play an important role in the nitrogen, carbon and sulfur cycles. And so they keep their small ecosystems running on shipwrecks, the impact of which is surprisingly widespread in the environment.

Microbial diversity at the bottom

Laila Hamdan of the University of Southern Mississippi and her colleagues in the Gulf of Mexico follow such processes. There is, for example, the wreck of the luxury yacht Annona, which sank in 1944 to examine. Since it was located more than 1,200 meters below sea level in the deep sea, this ship has turned into an island of microbial diversity. It does not end at the walls of the ship. Even at 200 meters from this wreck, typical wrecks are still found in the seafloor sediments.

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safe haven | Fishing around shipwrecks is rare. Therefore they are a relatively safe haven from humans and are also used by larger fish.

The team reached similar conclusions with one Experiment on two wooden sailing ships from the nineteenth century, which is also located in the depths of the Gulf of Mexico. The researchers placed pieces of pine and oak at different distances from them and collected them again four months later. Using DNA analysis, they then examined all the bacteria, fungi and other microorganisms that had settled on them in the meantime.

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Also in this case, the debris population invaded the new habitats in their vicinity. They reached their greatest biodiversity at 125 meters from the ships, but even on logs located 200 meters away their impact was still clearly visible. This is a surprisingly large radius. It is true that the natural structures in the deep sea also increase the biodiversity in their vicinity. However, in the case of a whale carcass that sank to the bottom, such an impact can only be detected up to a distance of about ten metres, about 100 meters around particularly species-rich sources of methane.

Three million wrecks asleep at the bottom of the sea

Apparently, many microbes make use of shipwrecks in a very similar way to dead wood or rocks: they find hard surfaces to which they can stick. It is rare in the rather monotonous world of sand and mud that characterizes the sea floor in many places. “We have known for a long time that solid natural substrates have a significant impact on the biodiversity there,” says Laila Hamdan. “But our study has now shown for the first time that human-made habitats also play a role in identifying microorganisms that settle on hard surfaces in their environment.”

This means that sunken ships could have a much greater environmental impact than has long been assumed. After all, according to estimates by the UNESCO World Cultural Organization, about three million wrecks sleep at the bottom of the oceans around the world. Each of these is a potential home to a rich microbial community. This in turn can create food and livelihoods for many other organisms. “Eventually, because of these biofilms, the hard surfaces of the ocean floor turn into diverse oases,” says Laila Hamdan.

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