Climate change and fisheries affect benthic composition and diversity in the North Sea - Investigations at the Dogger Bank during three decades (1991-2021)

Abstract

Abstract 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.