The influence of seabed geology on the nature and preservation of bottom trawl marks in the Bornholm Basin, southern Baltic Sea

IF 2.1 3区地球科学 Q2 OCEANOGRAPHY

Continental Shelf Research Pub Date : 2024-08-01 DOI:10.1016/j.csr.2024.105297

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Abstract

This study investigates six areas in a historically heavily trawled region of the southern Baltic Sea. Using acoustic geophysical mapping data and sediment cores from three field campaigns (2019, 2020, 2023), we evaluate and quantify the cumulative physical impacts from bottom trawling and the influence of seabed geology on mapped trawl tracks. The results are compared with fishing intensity data over three periods; 2012–2016, 2017–2019 and after the fishery closed. A correlation between fishing intensity and density of mapped trawl tracks exists in the soft sediments of the northern part of the area, while this link is weak in the less trawled southern part, where the seabed is characterized by more consolidated glacial clays and the high density of mapped trawl tracks reflects the preservation of tracks >8 years old. Four years after the closure of the fishery there were no signs of trawl-track degradation in any of the areas. In summary, mapped track densities alone are not a suitable measure of trawling intensity, considering the influence of seabed geology and the persistence of trawl tracks over time. Sediment deformation, observed by CT-scanning, indicates extensive remoulding and coarsening of the upper 20–40 cm of sediments in the trawled areas.

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海底地质对波罗的海南部博恩霍尔姆海盆底拖网痕迹的性质和保存的影响

本研究调查了波罗的海南部历史上拖网捕捞严重地区的六个区域。利用声学地球物理测绘数据和三次实地考察（2019 年、2020 年和 2023 年）获得的沉积物岩心，我们评估并量化了底拖网捕捞的累积物理影响以及海底地质对测绘拖网轨迹的影响。研究结果与 2012-2016、2017-2019 和休渔后三个时期的捕捞强度数据进行了比较。在该地区北部的松软沉积物中，捕捞强度与绘制的拖网轨迹密度之间存在相关性，而在拖网捕捞较少的南部地区，这种联系较弱，那里的海床特征是冰川粘土更加固结，绘制的拖网轨迹密度高，反映了轨迹保存了8年之久。休渔四年后，所有区域都没有拖网痕迹退化的迹象。总之，考虑到海底地质的影响和拖网轨迹的长期存在，仅凭绘制的轨迹密度并不能衡量拖网捕捞的强度。通过 CT 扫描观察到的沉积物变形表明，拖网区域上部 20-40 厘米的沉积物广泛重塑和变粗。

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来源期刊

Continental Shelf Research 地学-海洋学

CiteScore

4.30

自引率

4.30%

发文量

136

审稿时长

6.1 months

期刊介绍： Continental Shelf Research publishes articles dealing with the biological, chemical, geological and physical oceanography of the shallow marine environment, from coastal and estuarine waters out to the shelf break. The continental shelf is a critical environment within the land-ocean continuum, and many processes, functions and problems in the continental shelf are driven by terrestrial inputs transported through the rivers and estuaries to the coastal and continental shelf areas. Manuscripts that deal with these topics must make a clear link to the continental shelf. Examples of research areas include: Physical sedimentology and geomorphology Geochemistry of the coastal ocean (inorganic and organic) Marine environment and anthropogenic effects Interaction of physical dynamics with natural and manmade shoreline features Benthic, phytoplankton and zooplankton ecology Coastal water and sediment quality, and ecosystem health Benthic-pelagic coupling (physical and biogeochemical) Interactions between physical dynamics (waves, currents, mixing, etc.) and biogeochemical cycles Estuarine, coastal and shelf sea modelling and process studies.