Benthic fauna caught by ring dredge and 2 m beam trawl at the NATURA 2000 Sylt Outer Reef (SAR) and Borkum Reef Ground (BRG) sites in the North Sea are examined in relation to the intensity of mobile bottom-trawling fisheries. Samples were taken from 33 stations in the two areas, and the collected benthic fauna, consisting of infauna, epifauna, and demersal fish was determined. A total of 123 species were found, consisting of the phyla Chordata, Mollusca, Arthropoda, Echinodermata, Annelida, Cnidaria, and Bryozoa, with Chordata and Mollusca being the most species-rich phyla. The species compositions of BRG and SAR are relatively clearly separated. There was greater species diversity at BRG, likely due to lower fishing pressure from mobile bottom trawling than at SAR. Long-term data acquisition and analysis will be needed to visualize past and future changes in biodiversity

The Amrum Bank, a sandbank in the German Exclusive Economic Zone (EEZ) of the North Sea, accommodates a diverse marine ecosystem and is located northeast of the offshore wind farm (OWF) “Amrum Bank West.” In our study, we investigate epibenthic biodiversity by beam trawl and ring dredge catches at incremental distances to the wind farm. Using the same methodology, we compare biodiversity at the Natura 2000 marine protected area (MPA) “Sylt Outer Reef–Eastern German Bight,” where fishery has been excluded since March 2023, with surrounding locations that are still affected by fisheries. Both OWFs and MPAs prohibit fishing, but they have different primary objectives, with MPAs protecting biodiversity and OWFs generating renewable energy. The wind farm, where no fishing has been allowed since its operation began in 2015, may have been influencing epifaunal communities for several years. Our results indicate that the total number of individuals, the catch volume, and the Shannon–Wiener biodiversity index (Hs) increased with increasing distance from the OWF. The correlation between Hs and distance to the OWF as well as catch volume in correlation with the distance was statistically significant (p = 0.003 and p = 0.004). Furthermore, species composition varied between protected and non-protected stations. Multidimensional scaling revealed a higher similarity in species composition within the MPA compared to non-protected areas, which exhibited greater variability. When comparing stations closest to and farthest from the OWF, 16 species showed differences in abundance of at least 10 individuals, with 9 of these species being found exclusively or in higher numbers at the stations farthest from the OWF. Linear mixed-effects models confirmed that both distance to the wind farm and protection status had statistically significant effects on the abundance of several species, with a general trend of increasing abundance and biodiversity with increasing distance. However, no stations were sampled within the OWF itself because access was restricted by regulations, which limits the scope of our conclusions. This study provides important insights into the ecological dynamics of the Amrum Bank and emphasizes the need to give greater weight to anthropogenic factors in marine conservation and management strategies. The conclusions of this study apply specifically to the unique conditions of the Amrum Bank: soft sediment habitats, a degraded seafloor recovering from industrial fishing, and bottom-fixed turbines. We conclude that OWFs could be accompanied (or surrounded) by MPAs in order to provide areas in which epifaunal biodiversity can thrive without disturbance, which ultimately increases ecosystem health and resilience. However, it is also important to note that other studies have shown that OWFs can negatively affect MPAs, depending on local ecological conditions, and this warrants further investigation.

The response of benthic habitats and organisms to bottom-contact fishing intensity is investigated in marine protected areas (MPAs) of the German EEZ in the North and Baltic Seas. We examined the current state of macrofauna biodiversity in 2020–2022. Comparative analysis for macrofauna (in- and epifauna) inhabiting nine Natura 2000 MPAs constitutes a baseline to assess the effects of bottom-contact fishing exclusion in the future. Aspects of spatial and temporal variability are briefly summarized and discussed. We provide a species list for each region, including 481 taxa, of which 79 were found in both regions, 183 only in the North Sea, and 219 only in the Baltic Sea. The Baltic Sea dataset surprisingly included higher numbers of taxa and revealed more Red List species. The share of major taxonomic groups (polychaetes, bivalves and amphipods) in species richness showed peculiar commonalities between the two regions. In the North Sea, multivariate analysis of community structure revealed significantly higher within-similarity and stronger separation between the considered MPAs compared to the Baltic MPAs. Salinity, temperature and sediment fractions of sand were responsible for over 60% of the variation in the North Sea macrofauna occurrence data. Salinity, mud fraction and bottom-contact fishing were the most important drivers in the Baltic Sea and, together with other considered environmental drivers, were responsible for 53% of the variation. This study identifies aspects of macrofauna occurrence that may be used to assess (causes of) future changes.

This study investigates the long-term trends and potential drivers of changes in the epibenthic community at the “Dogger Bank” to clarify the effects of rising sea temperatures and trawling activities on epibenthic species composition and biodiversity. Over three decades (1991–2021), the epibenthic megafauna (> 1 cm) has been regularly sampled in summer with a 2-m beam trawl at five stations at the Dogger Bank tail end, and the epibenthic species abundances were quantitatively recorded. Furthermore, sea temperature and trawling effort datasets for the corresponding area were used to check for correlations with the species composition and abundances. The study relies on long-term data analysis and the application of multivariate statistical methods to discern temporal trends and the relative contributions of environmental and anthropogenic factors to community changes. This study hypothesizes that the benthic species community at the MPA on the Dogger Bank has undergone significant shifts over three decades due to rising sea temperatures and pressure from bottom contact fisheries. While local summer temperatures of the bottom water layer increased by up to 4 °C throughout the research period, trawling efforts rather decreased continuously in the area. Despite low interannual differences in species composition between the stations, we found the faunal regime to be under constant change (MDS, CCA), with a decrease in biodiversity (Shannon–Wiener indices) along with a general faunal regime shift around the turn of the millennium. We did not detect a linear correlation between biodiversity and temperature/trawling effort; however, we did find certain species positively or negatively correlating with these factors when using Spearman’s rank analysis. Our results provide a solid benchmark for future research in the German and neighboring Exclusive Economic Zone.

Over a period of 30 years (1991–2021) benthic fauna was monitored at a long-term sampling station at the NATURA2000 marine protected area Dogger Bank and at a reference station in Dutch waters, using a ring dredge and a 2 m beam trawl. Changes of benthic diversity of 127 species were detected in 238 temporally distributed samples and correlated with temperature and intensity of bottom fishing. Our results provide a solid benchmark for future research in the German Exclusive Economic Zone. During the timeframe of our study, the temperature at depths below 30 m remarkably increased by 4°C, while fishing pressure in the studied ICES rectangles decreased over the past 30 years from over 100.000 h of trawling per year to about 20.000 h. The numbers of benthic individuals sampled each year show a negative trend, while the number from 1991 to 2001 is first more influenced by fishing, later by temperature. An analysis of the benthic fauna at some stations adjacent to the long-term sampled station, sampled in 2021, showed that species composition is comparatively uniform over space and that therefore long-term sampling of one station can be used as a proxy for its surroundings in this area.