Shipping and fishing are omnipresent on the Baltic Sea. However, the long -lasting traces that leave such human activities on the sea floor are invisible from the shore. As a new study now shows, around a third of the southwestern Baltic Sea is crossed by deep furrows and dents, especially through the use of basic towing laws. These structures can shape the sea floor over the years and thus significantly change the ecosystem, as the researchers report.
With its long sandy beaches and iconic beach chairs, the Baltic Sea is one of the most popular holiday destinations in Germans. But the region is not only productive for tourism: fishing and shipping also play a major role there – but with consequences for the sea floor. Because anchors, basic lugs and submarine cables leave visible traces on the bottom. But how big is this problem?
Looking for traces on the sea floor
Researchers around Giuliana Andrea Díaz-Mendoza from the University of Kiel have now examined the extent of man-made traces on the sea floor of the Baltic Sea. For this purpose, the team in the southwestern Baltic Sea analyzed an area of 2189 square kilometers, which also included the Kiel and Mecklenburg Bay and the Flensburg Fjord. Díaz-Mendoza and her colleagues with the help of so-called hydroacoustic methods examined this area. So by analyzing the spread and reflection of sound waves in the water, they were able to create a three -dimensional map of the sea floor and also indicate its specific causes in most man -made traces.
The result: “The hydroacoustic recordings show significant changes in the sea floor, which were caused by many different human activities,” reports Díaz-Mendoza. Accordingly, around 36 percent of the areas recorded are affected. With 91 percent the largest share had basic towing fishing and special harnesses for shell traps. Sometimes the line -shaped furrows, both typically cause, were persecuted over several kilometers. The fishing devices left up to 20 centimeters deep and three meters wide. Repeated towing fishing can lead to even wider and deeper furrows, as the team explains.
Long -lasting changes
In addition, the researchers at the sea floor came across the impressions of anchors, up to four meters wide and 50 centimeters deep, as well as shipwrecks, submarine cables, pipelines and various other traces. These man -made structures were found primarily in fine -grained sediments, but also in sandy, mixed and coarse -grained areas. As Díaz-Mendoza and her colleagues report, many of these traces of human use are visible on the sea floor years later, for example, the impressions of anchors for at least 14 years.
“These activities represent a cumulative burden on the marine ecosystems and can lead to a change or loss of habitats,” warn the researchers. “Understanding not only the spatial expansion, but also the long-term effects of physical stress on the sea floor is therefore essential in order to achieve a sustainable balance between human activities and the stability of the marine environment,” says Díaz-Mendoza.
Source: Christian-Albrechts-Universität zu Kiel; Specialist articles: Continental Shelf Research, DOI: 10.1016/J.CSR.2024.105362