Shifting baselines for soft sediment fauna in the Belgian coastal area?

Situated within the southern North Sea, the Belgian marine realm forms a unique marine ecosystem, characterised by several shallow sandbanks and gullies. Like other systems, the Belgian part of the North Sea (BPNS) underwent major changes during the past decades, largely related to the continued increasing impact of different human activities and potentially due to climate change. To properly assess the impact on the benthic marine ecosystem, it is essential to gain insight in the natural variability of the different ecosystem components.
For this study, we used yearly monitoring data, sampled each autumn between 1985 and 2013 at different locations in the BPNS. Long-term trends in the macrobenthos, epibenthos and demersal fish communities as a whole are shown, as well as for some apparent species. As expected, year-to-year variability was high for all three ecosystem components. However, Principle Component Analyses showed clear shifts for the three different ecosystem components. Such shifting baseline was most clear in the offshore fish community around 2002 and the nearshore macrobenthic community around 2003, the latter mainly related to the sudden appearance of the tube-building polychaete Owenia fusiformis. Within the epibenthic community, netted dogwhelk Nassarius reticulatus first appeared in 1995 but established a permanent population since 2001. Other species like common brittle star Ophiura ophiura and hermit crab Pagurus bernhardus were present in Belgian waters but really increased since 2004. The BPNS is a highly dynamic system characterised by a high variability in densities, however some trends, mainly in the fish community, indicate a climate-induced increase of typical southern species like lesser weever Echiichthys vipera, scaldfish Arnoglossus laterna and red mullet Mullus surmuletus after 1996-1997.
Some clear general shifts throughout the soft sediment coastal ecosystem could be observed, due to changes in physical and climatic parameters, but most observed patterns were species specific.