MEPS 609:17-32 (2019)  -  DOI: https://doi.org/10.3354/meps12802

ABSTRACT: Bioturbation is one of the most important processes for benthic-pelagic coupling and biogeochemical fluxes in marine sediments, such as the intake, transport, and preservation of organic carbon. However, only little is known about the large-scale and long-term variability of community bioturbation potential (BPc) and trait diversity of south-eastern North Sea (NS) macrofauna communities in relation to anthropogenic and environmental parameters. Here we pooled macrofauna species with similar life traits into functional groups, revealing the main functionality of a benthic ecosystem. The BPc and trait diversity of south-eastern NS macrofauna communities, derived from the NS Benthos Survey in 1986, the NS Benthos Project in 2000, and a more recent study from 2010-2015, were analyzed and compared. Significant changes in spatial variability of BPc were found, simultaneously to regionally decreasing BPc, e.g. in the central parts of the Oysterground, while BPc increased in other areas, e.g. along the North Frisian coast. Contrastingly, the spatial variability of trait diversity has remained stable since 1986. Overall, the study area was dominated by the functional group ‘biodiffusors with slow free movement.’ During the 1986 study period, we identified 3 basically different trait-based communities, i.e. the Dogger Bank, Oysterground, and coast community. Long-term analyses based on these 3 trait-based communities revealed changes in dominance of functional groups within each of the communities up to 2010-2015, which were related to anthropogenic pressures such as fishery and seabed degradation, synergistic to increasing sea surface temperature, food limitation, and de-eutrophication.

KEY WORDS: Long-term variability · North Atlantic Oscillation Index · Trait analysis