Human use of the marine environment of the Baltic Sea is visible on the seabed and can significantly impact the habitat of many marine species. In a new study, researchers from Kiel University have used high-resolution hydroacoustic methods to investigate the seafloor in the southwestern Baltic Sea for human traces.
According to the study, around 36% of the investigated areas show various influences on the seabed caused by human activities such as bottom trawling, shipping, anchor marks and dumping. The findings, published in the journal Continental Shelf Research, raise critical questions about the ecological resilience of this marine habitat, whose potential for recovery is poorly understood. According to the study, man-made features on the seabed can persist for more than a decade, suggesting slow regeneration.
Hidden traces of human activity
The data collection covered an area of 2,189 km2, mainly in the Kiel Bight, the Mecklenburg Bight and the Flensburg Fjord.
“The hydroacoustic images clearly show seabed alterations caused by different human activities,” says Giuliana Andrea Díaz-Mendoza, first author of the study and doctoral researcher in the Coastal Geology and Sedimentology working group at CAU.
More than 91% of the recorded human impacts were caused by bottom trawling, especially by trawl marks from otter trawls and dredge marks, such as mussel dredges. The researchers also found numerous other anthropogenic traces, including anchor marks, cables, pipelines, trenches and also of unknown origin. Fine-grained sediments are particularly affected, but human structures can also be found in sandy, mixed and coarse-grained sediments.
Hydroacoustic data collection: The key to achieving precision
Data from different sources was used and complemented by additional high-resolution hydroacoustic mapping of the seafloor using multibeam echosounders and side-scan sonars. The team compared this data with satellite-based information and other existing data sources on hotspots of human activity in the southwestern Baltic Sea.
“Previous regional assessments based on ship traffic information do not see the actual human footprint,” explains Professor Dr. Christian Winter, head of the Coastal Geology and Sedimentology working group and supervisor of the doctoral project. “Our high-resolution hydroacoustic mapping now reveals even the smallest disturbances on the seafloor and underlines the importance of precise data collection,” Winter continues.
The new study brings together, for the first time, all the data that helps researchers to understand the physical footprint of the southwestern Baltic Sea. It provides an essential basis for better estimating the pressures on the seabed in the future.
“Understanding not only the spatial extent but also the long-term effects of physical pressures is essential for achieving a sustainable balance between human activities and the stability of the marine environment,” concludes Díaz-Mendoza.
The results of the study highlight the need for further research.
More information:
Giuliana Andrea Díaz-Mendoza et al, Hotspots of human impact on the seafloor in the Southwestern Baltic Sea, Continental Shelf Research (2024). DOI: 10.1016/j.csr.2024.105362
Citation:
Hydroacoustic imaging shows human traces on the seabed may be visible for decades (2025, March 20)
