Quantifying pelagic-benthic coupling in the North Sea: Are we asking the right questions?

The coupling between pelagic and benthic processes occurs through the signals sent between the water column and the seabed. Huge methodological challenges are associated with the quantification of the signals being sent between these two domains — especially in a relatively shallow and heavily fished region such as the North Sea where deployment of sediment traps or bottom mounted cameras or samplers is difficult. Thus, there are relatively few sites in the North Sea for which good data are available for describing pelagic-benthic (or near shore-offshore) coupling and considerable effort is devoted to obtaining more and better data describing this exchange. Efforts to quantify exchange between the water column and the sediment must continue. However, such studies will not, in themselves, lead to a quantification of pelagic-benthic coupling in the North Sea. We identify here other areas of study that we consider to be important in order to, ultimately, quantify the pelagic-benthic coupling on the basin-scale. Current knowledge on regional annual differences in new production (i.e., that which leads to the production of new organic material and, ultimately, sedimentation from the water column to the seabed) in this region is reviewed. Differences in the magnitude of new production can be predicted to influence both the physical/chemical characteristics of the bottom and benthic communities. As these differences are under the control of local and regional oceanographic processes, it is argued that these processes will also influence pelagic-benthic coupling and attention should be given to these geographical differences when considering benthic-pelagic coupling. Evidence is also presented that interannual climatic variability, such as the North Atlantic Oscillation (NAO), influences pelagic-benthic coupling in the North Sea. The influence of climate variability in establishing conditions for benthic communities is also identified as a neglected region of study that is crucial in order to understand and quantify the coupling between pelagic and benthic communities. Finally, the paper considers whether the organic signal reaching the benthos might be most readily interpretable through measurement of meiofaunal biomass and activity, rather than through the more common practice of examining the macrofaunal benthos community. The meiofauna has been shown to be important in the flux of energy and nutrients. We argue that foraminiferans may deserve more study in this respect. Their large numbers in combination with structural and physiological adaptations suggest that these organisms may be of greater importance than other meiofaunal organisms of comparative size and abundance.