There are tens of thousands of mysterious holes in the bottom of the North Sea. It was assumed that they are formed when, for example, gases leave the seabed. But new research now reveals that in some cases things are very different…
In many cases, gases that do not escape from the seabed, but porpoises appear to be the culprit; Scientists have come to this conclusion after long and extensive research using many different scientific disciplines. For example, when hunting for sand eels, porpoises leave small dents about 11 centimeters deep. These dents can eventually develop into pits of up to 50 meters. The results are therefore very important, because these deep wells can ultimately have a major effect on the various ecosystems present in the sea.
Liquids
Previously it was thought that wells were at the bottom of the sea, also called pockmarks always formed by liquids and gases that left the seabed. New research shows that this is not always the case. For example, there are many sand eels in the seabed and porpoises leave these holes behind when they have been hunting. These dents resemble so-called pockmarks, but are a lot less deep and therefore not the same. Scientist Jens Schneider von Deimling helped with the research. He says: “Our results show for the first time that these dents in the seabed are directly caused by the way in which porpoises and sand eels behave. The dents are therefore not only caused by rising liquids.” The research has been published in the journal Communications Earth & Environment.
Porpoises on the hunt
The scientists used a combination of different techniques for the research. For example, they used a very modern depth sounder, they looked at the behavior of porpoises and they even used satellites. Ultimately, they discovered 42,458 wells in the examined North Sea area with an average depth of 11 cm. The scientists found it striking that these pits were mainly found in breeding areas of sand eels. This confirmed their hypothesis that certainly not all wells in the seabed are caused solely by rising gas and bottom water. “We had to come up with an alternative hypothesis that could explain where these wells come from,” Schneider von Deimling explains. “This ultimately allowed us to predict where possible hunting areas for porpoises should be located, and that is exactly where we found the wells: always near areas where sandeels live.”
Green energy
The scientists suspect that the small wells can eventually develop into much larger wells of up to 50 meters deep. This is important to know because it can have major effects on how marine ecosystems develop. “In the long term, the results will be of great importance, especially from a geological and biological point of view,” says Schneider von Deimling. “The results can thus be used to better assess the ecological risks of green energy in the sea. In this way, marine life can be better protected.”
In addition, it is now becoming clear that the many small dents in the ocean floor ultimately have a major effect on how much sediment is moved in an area. For example, initial calculations show that approximately 773,369 tons of sediment have settled in the surveyed area of 1,581 km2 alone. That amount of sediment is about as heavy as 500,000 cars. Although the porpoises themselves are only interested in hunting for sand eels, they also initiate processes that ultimately literally shape the bottom of the ocean.
2024-01-02 18:04:40
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