Dynamics of trophic pathways

From an anthropogenic viewpoint ecosystems with large phytoplankton, short food chains and rapid channelling of energy to fish are considered efficient energy pathways, while inefficient energy pathways are characterized by high metabolic loss, long food chains and gelatinous apex predators.

The structure and functioning of microbial food webs and zooplankton communities are essential determinants of whether energy are lost to human food supply or production by ending up in microbes and gelatinous organisms or in harvestable resources. The fate of primary production and the structure of pelagic food webs are influenced by human activity, including nutrient supply, changing ocean colour, harvesting practices and ecological dynamic responses of the many components of the ecosystems. In a combined field, laboratory and modelling approach the Hjort Centre will determine i) what structures microbial food webs, ii) the role of zooplankton in linking the flow of energy from primary production to higher trophic levels and iii) trophic energy transfer in pelagic food webs.

Relevant projects involving Hjort Centre members

MicroPolar[μP]:Processes and Players in Arctic Marine Pelagic Food Webs - Biogeochemistry, Environment and Climate Change
Project leader: Gunnar Bratbak, University of Bergen and Aud Larsen, Uni Research
Funding source: RCN
Period: 2013-2017

The interaction between the biosphere, the atmosphere and the hydrosphere is mediated by microorganisms being the main drivers of biogeochemical cycles in the ocean and the main producers and consumers of inorganic nutrients, organic carbon and CO2. The MicroPolar [μP] project focuses on marine microbial food webs and biogeochemical cycles in the Arctic Ocean and will provide a better description and understanding of the organisms, the processes, and the feedback mechanisms that shape these interactions.

PAVE: Atlantic Water Pathways to the Arctic: Variability and Effects on Climate and Ecosystems
Project leader: Agnieszka Beszczyńska-Möller, Institute of Oceanology, Polish Academy of Sciences (IO PAS), Sopot, Poland (local contact person: Annette Samuelsen)
Funding source: Norway Grants under the Polish-Norwegian Research Programme
Period: May 2013 – April 2016
Norwegian Partners: Institute of Marine Research; Nansen Environmental and Remote Sensing Center

PAVE is a multidisciplinary research project focused on investigating the response of the Arctic sea ice and biological environment to variability and recent warming of the Atlantic Water (AW) inflow through the Fram Strait and the Barents Sea. In this project the interannual variability in zooplankton abundance and community composition in relation to inflow of Atlantic water in the Barents Sea and Fram Strait is investigated. A high-resolution coupled physical-biological model for the Fram Strait is developed in the project.
Web link: http://www.iopan.gda.pl/projects/PAVE/

LOTROMIX: Lower trophic level mixed fishery; implications for ecosystem and management
Project leader: Espen Strand, Institute of Marine Research
Funding source: RCN
Period: 2015 – 2017
In collaboration with: Norwegian University of Science and Technology, Norway; University of Stirling, Scotland; Dalhousie University, Canada
Following a steadily increasing demand from the aquaculture industry for raw materials for feed production, there is an increasing interest in harvesting lower trophic level organisms as a new source for marine protein and lipids. Before a potential commercial fishery on lower trophic level species can be started, we need to establish sound scientific knowledge about the targeted ecosystem and assess the potential consequences posed by the harvest in order to manage such a resource within a sustainable framework. Economically viable harvest most often requires some sort of aggregation of biomass (i.e. spawning grounds, fish schools, overwintering area). One of the most promising aggregation of marine lower trophic level biomass is the mesopelagic layer, often referred to as the 'deep scattering layer' by the way it is observed on echo sounders. However, a fishery targeted at the mesopelagic layer would necessarily imply a mixed fishery as the layer consists of a wide range of species. The main goal of LOTROMIX will be to quantify the species composition, biomass distribution and production on a temporal and spatial scale in the Norwegian Sea and further analyze the quality of the catch for feed production and assess potential ecological consequences of mixed fishery on this unexploited resource.

TIBIA: Trophic interactions in the Barents Sea - steps towards an Integrated Ecosystem Assessment
Project leader: Hein Rune Skjoldal, Institute of Marine Research
Funding source: RCN (Strategic Institute program)
Period: 2014 - 2018

The primary objective of this project is to improve our understanding of the trophic interactions, food web structure and function, and energy flow in the Barents Sea ecosystem. Secondary objectives are: 1) Strengthen the theoretical and practical competence in, and develop methodology for trophic studies; 2) Design sampling program and process studies for trophic interactions based on best practice for survey sampling and data handling; 3) Quantify the production and energy flow through the Barents Sea food web and explore variation in time and space; 4) Improve the description of the Barents Sea food web structure and explore variation in time and space; 5) Quantify the trophic interactions of selected key species in the food web, their importance for energy flow, influence on individual growth, and the system carrying capacity, and 6) Synthesise and improve the knowledge base for food web dynamics in the Barents Sea to strengthen the input to Integrated Ecosystem Assessment.

CODFUN: The cod capelin interaction in the Barents Sea: spatial dynamics in predator-prey interactions
Project leader: Edda Johannsen, Institute of Marine Research
Funding source: RCN
Period: 2015 - 2018
The overall objective is to quantify and explain spatial heterogeneity in the capelin-cod interaction at different spatial scales in the Barents Sea. In this project we propose to use a combination of state-of-the-art ecological statistical modelling, multi-scale retrospective analysis, and a small-scale field study to investigate the capelin-cod interaction at different spatial scales. In addition to an increased understanding of a fundamental Barents Sea ecosystem process, we expect to be able to use the results to improve the formulation of natural mortality included in the existing capelin assessment model for the Barents Sea.

HALO: Harvesting lower trophic levels - Ecosystem effects and trade offs
Project leader: Espen Strand, Institute of Marine Research
Funding source: RCN
Period: 2014 - 2016

The overall objective of HALO is to quantify how harvest of lower trophic level organisms may affect ecosystem dynamics in the Norwegian Sea. The project will utilize an ecosystem model, NORWECOM.E2E to assess the feasibility of harvesting species on lower trophic levels and evaluate possible effects on higher trophic levels with special focus on already commercially exploited fish stocks.