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Trophic interactions in the pelagic environment

Research project
Active research
Project owner
Department of Biological and Environmental Sciences

Short description

I work on predator-prey interactions in planktons, physical-biological coupling and food web dynamics in the pelagic environment.


Peter Tiselius (professor)

Research interests

Predation in marine pelagic ecosystems

Predation is the ultimate evolutionary force that shapes all forms of life, also the smallest plankton of the sea. Food webs are formed as a result of predation and trophic cascades are observed in all places that one investigates. A constantly changing environment and organisms that grow fast and have short generation times create a rapidly changing ecosystem which efficiently use resources.

Controlling factors for this fundamental structure are the focus of my research. I use phytoplankton, ciliates, copepods and jellyfish as targets of my experimental work. I use high-speed video filming, manipulative bottle incubations and stable isotopes to investigate the predator–prey interactions. In the field, I coordinate a 35-year long monitoring programme measuring the production and structure of plankton every 2 weeks at three stations in the Gullmar Fjord.  

Production and fatty acids in pelagic food webs

Marine pelagic production all comes from small phytoplankton transforming light and nutrients to biomass. In the process, different fatty acids are formed and enriched up the food web. Seasonal changes in production is followed through 14C incorporation and the fate of this biomass is traced through the food web. Highest production occurs in the summer, but it also coincides with lowest biomass because predation is very high then.

The importance of trophic cascades in this system is investigated, and the pathway of fatty acids is an important goal for the research. The essential omega-3 fatty acids DHA and EPA are enriched in copepods and transferred to fish becoming invaluable nutrition for us.

Distribution of pollutants in coastal seas

Pollutants are the main threat to our oceans and many of the are highly toxic, very persistent and enter the food webs through adsorption to surfaces of the organisms. Feeding becomes a major uptake route for animals >1 mm, including most copepods. Pollutants also adsorb to marine aggregates called marine snow and sink to the bottom. By studying the structure and function of the food web, I predict where pollutants should end up in the sea. The two main endpoints are fish and the sediment, each with its significance for human health. By a combination of basic food web studies and well-known chemical characteristics of the pollutants, I predict where unwanted releases will end up.

Ongoing and previous projects

Ongoing projects

  • Long-term monitoring of primary production in the Gullmar Fjord

  • Trophic cascades in coastal zooplankton communities

  • Distribution of pollutants in a dynamic pelagic ecosystem

  • Non-lethal effects of krill on the diel feeding behaviour of copepods

  • Trophic interactions and diel feeding rhythms of microzooplankton in a productive Swedish fjord

Previous projects

  • Baltic Zooplankton cascades, BONUS+project 2009-2011

  • A new invader in the Baltic Sea—Feeding and ecosystem impact by the ctenophore Mnemiopsis leidyi

  • Assessment of community structure and seston quality effects on plankton carbon fluxes at two contrasting coastal sites

  • Density dependent grazing rates in a natural microzooplankton community