The research activities of Yngvar Olsen have basically been related to different aspects of nutrition of plankton organisms, the first 10 years in freshwater and later on in marine coastal water. Early work involved studies of uptake and use of mineral nutrient in phytoplankton and food intake and allocation in zooplankton. Later work includes more integrated ecological studies of planktonic food webs with a focus on the important functional plankton groups and their trophic interactions in coastal waters. Experimental studies have been most important, and culture systems include batch cultures and chemostat for single organisms, mesocosms for experimental ecosystems, and lakes/lagoons for full scale ecosystem experiments (publications)

The majority of the biological activity in the marine ecosystems (>90%) takes place in microorganisms of the planktonic food web, which includes organisms feeding on at least 4 different trophic levels (level 1-4). This is different in terrestrial ecosystems where carnivores eating other carnivores (trophic level 4) are not that common. The functional and structural characteristics of the planktonic food web are most important for the environmental state of the marine ecosystem, for its productivity and fishing yields, and for its ability to take up and sequester carbon through the so called “Biological Carbon Pump” (see Figure). Plankton nutrition and interactions between organisms and functional groups are instrumental for a fully understanding all these aspects.

Fields of research related to plankton nutrition

• General mechanisms of coastal eutrophication - over-fertilization of coastal water leading to unacceptable environmental state in coastal waters
• Environmental influence of salmon aquaculture on surface water ecosystems, carrying capacity of production
• Planktonic stages of salmon lice, transfer mechanisms in and in between stocks of salmonids
• Lipid nutrition in fish larvae (classified as plankton) and juveniles
• Rotifer culture and their lipid/phospholipids metabolism, lipid enrichment procedures
• Lipid and mineral nutrition of copepods; with focus on red feed Calanus finmarchicus
• Experimental studies of microalgae; growth characteristics and biochemical composition

Fields of research related to aquaculture ecology

• Integrated multi-trophic aquaculture (IMTA), salmon driven with a focus on waste generation of salmon and macroalgae in IMTA
• Nutrient physiology and growth characteristics of farmed and wild macroalgae

MsC and PhD studies can be advised within all mentioned fields of research.