WP 4. Pelagic-benthic coupling
WP leader: Lis Lindahl Jørgensen
WP4 will examine how the benthic and pelagic systems are coupled by analyzing stable isotopes (carbon and nitrogen) and fatty acid signatures in addition to traditional stomach analyses of major fauna components. This will be done in three selected regions in the southern (Atlantic), central (Polar front), and northern (Arctic) Barents Sea. The more detailed studies in WP4 will supplement the studies in WP5 and WP6, while drawing upon data and results from WP2 and WP3.
Food-web parameters can provide information which may help predict the relative stability of a system when subjected to biotic or abiotic changes. The important ecosystem components included in WP4 will be identified from pelagic and benthic baseline mapping done in the joint Russian-Norwegian Ecosystem Surveys (2006-2013) and in sampling of benthic stations in the Barents Sea done primarily by PINRO. WP 4 will identify the primary food source, trophic pathways and relative trophic position of benthic and pelagic species by using stable isotopes. Stable isotope analysis has been used to examine marine food webs since the 1980s (Fry 1988) and has become increasingly more used in ecological studies of the Arctic (e.g. Dunton et al. 1989, Lovvorn et al. 2005, Tamelander et al. 2006, Renaud et al. 2011). This method complements more traditional food web study techniques (such as stomach content analysis, feeding experiments and in situ observations), by providing a longer integrated history of feeding. The use of stable isotopes will be explored in collaboration with a PhD/PostDoc position and a team consisting of Professor Beverly Johnson from Bates College, Lewiston, USA, Dr. Paul Renaud from Akvaplan-niva, Tromsø and Professor Jørgen Berge from the University of Tromsø. A pilot study was made in 2012 in Isfjorden at Svalbard which showed that a mixture of multiple carbon sources constituted the diets of the primary consumers and possibly the entire benthic food web (Løkken 2013). The resolution of the stabile isotope method in resolving differences in trophic level position can be limited and the method will therefore be used in combination with other methods, including fatty acid analysis, feeding experiments, and direct observations (Nilsen et al. 2008b).
The pelagic-benthic coupling will be investigated within well-defined case-studies
selected in the i) southern, ii) frontal, and iii) northern Barents Sea. It is planned that these cases will be complemented by three similar case studies in the slope regions west and north of Svalbard in the SI for the Arctic Ocean. Important species in terms of abundance or biomass, or in their roles as predators or prey, will be identified and sampled to obtain stable isotopes, fatty acid composition, and stomach content data. The species will include phyto- and zooplankton, benthos (infauna and epifauna), and fish, and possibly also marine mammals and birds. The sampling design including the number of stations in each case will be determined as part of the planning work in WP2.
The main aim of the WP4 will be to deliver answer to some of the focal questions:
- Who are the main species that contribute to the pelagic-benthic coupling?
- What are the primary food sources for the pelagic-benthic- food web coupling?
- What are the trophic pathways and relative trophic positions of the species that make up the pelagic-benthic coupling?
- How persistent is the pelagic-benthic coupling under changing climate conditions?