School of Natural and Environmental Sciences

Projects

Benthic-pelagic coupling in North Sea food webs

The project aims to apply stable isotope approaches and collaborate with other studies to increase understanding of the importance of terrigenous matter and benthic-pelagic coupling processes across whole food webs across high and low trophic levels in food webs. The specific objectives are to:

  1. Characterise potential source materials by determining 13C, 32S and 15N data of planktonic and benthic primary consumers and producers, and compare these with the signatures of marine and estuarine source materials using mixing models; 

  2. Describe spatial and temporal variability in the source materials (from the microbial domain to metazoans) and relate these to water mass characteristics; and 

  3. Trace the uptake of sources by different consumers at higher trophic levels at different temporal and spatial scales.

Continental shelves and slopes comprise <20% of the marine area, yet may account for up to 50% of marine productivity, with fisheries traditionally thought to be supported by pelagic primary production, and subsequent mixing. However a substantial role in secondary productivity is now ascribed to benthic production, and food web models that explicitly consider energy flow from both pelagic and benthic sources will provide a more realistic energy flow template for understanding of food-web basal materials in shelf systems. The pelagic and benthic systems which compose the marine environment are the focus of two rather separate research disciplines. Compared to knowledge of the structure of these systems, that of the processes existing within and between them is very poor. Among the processes that need to be better defined are terrigenous C and N inputs, their availability to higher trophic levels via pelagic and benthic food webs and the spatial and temporal variability of these.

 

While 13C conveys information about materials sources, 15N is a useful indicator of trophic position. Most food-web reconstruction based on stable isotope ratios is currently limited to the higher part of the food web, because standard isotope ratio mass spectrometers requires physical separation of the organisms (handpicking). Current development based on the isotopic characterisation of molecules specific for certain micro-organisms recently allow resolving food-web relationships in the lower part of the food web.