Publication Abstract

Key processes driving benthic-pelagic coupling in the North Sea: linkages between fieldwork and modelling for a new observational programme

Key processes driving benthic-pelagic coupling in the North Sea: linkages between fieldwork and modelling for a new observational programme

John Aldridge*, S. Painting*, R. Parker*, D. Mills* and P. Kershaw*

A 1D version of ERSEM/BFM (Biogeochemical Flux Model) was used to identify which critical field measurements should be made during a planned field study of ecosystem structure and function in the North Sea (see poster by Painting et al). Simulations were undertaken to:

• Prepare carbon and nitrogen budgets in order to identify the main pathways for carbon and nutrient flow;
• Test the importance of benthic-pelagic coupling on productivity;
• Guide fieldwork with regard to the key process measurements required for model validation.

Results are shown for the last two years of a 12 year run, set up to reproduce conditions at the Oyster ground (summer stratified, water depth 45m). After 12 years most quantities show a repeating annual cycle. However, benthic organisms show evidence of weak cycles at longer time scales of two years or more – possibly generated by predator prey interactions. For the purpose of presentation, ERSEM functional groups within the phytoplankton, zooplankton and benthos compartments have been summed to yield aggregated phytoplankton, zooplankton and benthic biomass and fluxes.

The importance of benthic-pelagic coupling was assessed by ‘switching off’ chemical and biological processes in the sea bed. When switched off, the bed acts as a passive sink for pelagic detrital material, with no return of any material to the pelagic system. This had a clear effect on primary and secondary production, with reduced biomass throughout the summer, and a much weaker autumn bloom. The annual decrease in available carbon, considering both the microbial loop and primary production, was around 15%. The same simulations were also done based on a mixed water column with the same depth of 45m. This showed an almost identical relative decrease in available carbon in the absence of the benthic recycling of nutrients.  A simulation for a shallower mixed water column of 35m was also carried out. As expected, the results show a greater influence of  benthic recycling of nutrients, leading to ~25% decrease in zooplankton biomass over an annual cycle

Reference

John Aldridge*, S. Painting*, R. Parker*, D. Mills* and P. Kershaw* (2007) Key processes driving benthic-pelagic coupling in the North Sea: linkages between fieldwork and modelling for a new observational programme. ICES Annual Science Conference in Helsinki, Finland September 2007

John Aldridge*, S. Painting*, R. Parker*, D. Mills* and P. Kershaw*

ICES Annual Science Conference in Helsinki, Finland September 2007