Research Interests

Analysis and Control of Microbial Systems

Research Interests

Lab interior: Just having a break - back soon. Photo: Madeleine Gundersen.

Management of natural ecosystems

  • Structure and functioning of planktonic ecosystems
  • Eutrophication

Management of engineered ecosystems

  • Biological water treatment
  • Biofilm formation and fouling


  • Host/microbe interactions in fish
  • Microbial management of marine fish larvae
  • Water quality in aquaculture
  • Recirculated aquaculture systems (RAS) 


  • Production of biogas

For earlier research interests, see The archives.

Management of natural ecosystems

Structure and functioning of planktonic ecosystems

Key words: Food web interaction, stability, omnivory, limiting factors, predation.

This research involves several groups at NTNU, started in limnetic systems, but is now focused on marine systems. All functional groups of plankton have been studied, and research has been funded by the Research Council of Norway and some smaller agencies. A large number of master and dr students have been educated within the field, and partly with international collaboration (CSIC, Spain; Leibnitz Int Mar Sci, Germany; Univ München, Germany, Finnish Environment Institute, Finland).

Ongoing activity is related to limiting factors for heterotrophic bacteria in Arctic waters (partly financed by The Norwegian Svalbard Society) and ecological effects of harvesting zooplankton (cooperation with Dept Biology and Inst Marine Research, Bergen, and financed by the Research Council of Norway).


Key words: Nitrogen and phosphorus loading, biological responses, ecosystem experiments.

The work is strongly linked to the work on "Structure and functioning of planktonic ecosystems", by its focus on plankton and on biological mechanisms of significance for the ability of the plankton to manage nutrient loading. The link also relates to international cooperation and to funding. We have also been involved in an EU funded project, COMWEB, on marine eutrophication.

Ongoing activities are mainly related to publication of results from previous projects, and include data from a five-year full scale eutrophication in the land-locked bay Hopavågen.

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Management of engineered ecosystems:

Biological water treatment

Key words: Nutrient removal, EBPR, nitrification, gel entrapment, process water.

Enhanced biological phosphorus removal EBPR and P sludge analysis related to Swedish NUTEKs STAMP program was combined with denitrification at full scale UCT and in lab. Gel entrapped nitrification project "New immobilization techniques for biological wastewater treatment" (NFR) supported one PhD 1999. Fluorescence in situ hybridization FISH applied to quantify nitrifying community dynamics modelled by cellular automata. Gel technology also includes studies of freezing / drying for long-term storage and reactivation, as well as developing gel microbeads for superactive airlift reactors.

Current activities focus on molecular techniques to analyze nitrifying communities at high salinities, related to nitrifying biofilms applied in recycled marine aquaculture. Also, total N removal from process water after post-combustion CO2 capture by amine absorption is investigated in cooperation with Sintef Process Technology .

Related Master projects have been performed at Department of Civil and Environmental Engineering NTNU, Hydro Research Center Porsgrunn, Lunds University, TU Delft (including Anammox) and University of Nijmeegen. 

Biofilm formation and fouling

Key words: Chitosan, flocculation, adhesion, non-solid surfaces, hydrogels, marine biofouling.

Activity based on earlier NTNF projects, leading to projects "Biopolymers in biofilm and flock formation" (NFR/Jotun) with one PhD finishing 2001, and "Marine Biofouling" (Jotun/NFR) with one PhD in 2002. While polycation-cell interaction studies have concentrated on chitosans, marine biofouling include microbial adhesion to gel surfaces as well as development of suitable controlled shear test systems for fouling-release regimes on low energy surfaces LES.

Related Master projects have also been performed at TU Delft, Montana State University Bozeman and at Florida Institute of Technology FIT supported by Jotun.

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Host/microbe interactions in fish

Key words: Mutualism/commensalism/parasitism, host gene expression.

The normal interactions between host and microbes are of a mutualistic or commensal nature, and the unnormal situations are those with parasitism involving pathogens. For studies of host/microbe interactions in an aquaculture context there has been a bias towards studies of the unnormal situations (pathogens), which partly relates to the low survival generally observed for marine fish. However, better knowledge on the role of microbes in healthy animals will serve as knowledge basis for microbial management strategies.

Our work has focused on how microbes enter the gastro intestinal (GI) tract, the speed of colonization, and individual variation in GI tract colonization. More recently we have extended the work to studies on the impact of the microflora for digestion/nutrition, the development of bacteria free larvae to do rearing under gnotibiotic conditions, microbial diversity/pathogen invasion relationships, and gene expression in the fish regulated by differences in the microbiota. Ongoing activities are mainly related to the Codtech and the Promicrobe projects.

Microbial management of marine fish larvae

Key words: Microbial management strategies, microbial maturation, probiotics, disinfecton of eggs, grazer control of microbes, immunostimulation, manipulation of microflora in live feed, microalgae/microbe interactions.

For many marine larvae the rearing is associated with low and variable growth and survival, and lack of reproducibility within and between egg batches. Detrimental larvae/microbe interactions seem to be a key cause for these observations. Based on an ecological analysis of rearing systems we have hypothesized that due to high densities and system perturbations there is a selection for opportunistic species (r-strategists) in today's aquaculture systems, with detrimental host/microbe interactions as a consequence. Based on this analysis we proposed a general strategy and methods for microbial control already in 1993 (Vadstein et al. 1993), and have used that as a research strategy since. Early work focused on methods for surface disinfection of fish eggs, development and testing of the Microbial Maturation concept, methods for classification of microbial communities on a r/K-axis, the use of live feed as vectors for probiotics, evaluation of bacteria as candidates as probiotics, and microalgae as modulators of microbial communities. Four PhDs and a large number of Master students have graduated within this topic.

Previous activities have been funded by the Research Council of Norway, the European Commission, and industry. Ongoing activities are mainly related to the Codtech and the Promicrobe projects. Within this research there has always been a strong national and international cooperation (among others Glasgow Univ, Scotland; Gent Univ, Belgium; Wageningen Univ, Netherlands; Ifremer, France).

Water quality in aquaculture

Key words: Physiochemical quality, microbial quality, Microbial Maturation, recirculation.

Water quality is a fuzzy expression where we have given attention to particles and particle removal, ammonia and nitrification, and microbial quality. At this stage there is no knowledge to classify microbial species on a quality axis, thus we have used the r/K-strategist concept from ecology as a basis for evaluation of microbial quality – dominance of K-strategists indicate good quality and dominance of r-strategists poor quality. We developed the Microbial Maturation Concept where a biofilter is used for controlled recolonization by K-strategist after disinfection or ultra-filtration of the water. Test with yolk sac larvae and during first feeding have demonstrated better survival and growth with Matured water, and effects that are as strong as addition of antibiotics to the water. Later, partly based on experience with recirculation for rearing of sea bass, we have proposed that also recirculation is a technology by which K-selection is obtained. At present we are testing this hypothesis. As a consequence we have also started research on nitrification in seawater, which seem to differ from nitrification in fresh-water.

Previous activities have been funded by the Research Council of Norway and industry. Ongoing activities are mainly related to the Codtech and the Promicrobe projects.

Recirculating aquaculture systems (RAS)

Key words: water treatment, land based aquaculture, microbial control

Almost all new land based aquaculture systems being planned and built in Norway today are Recirculating aquaculture systems (RAS). In contrast to traditional flow through systems, RAS have a reduced water usage, more concentrated waste streams and the possibility for increased control and more stability of the physicochemical and microbial water quality. The water is treated both mechanically and biologically (with bacteria in bioreactors) and then reused in RAS. Microorganisms are highly involved in many facets of RAS. For example, the production of fish in RAS depends on the function of the bioreactors. In addition, biosecurity and microbial control in to and within the RAS is critical for optimal and stable production of fish. Since RAS are popular, commercial, complex and intensive biological systems that may be controlled and manipulated, and where the microbial community is of paramount importance and involved in numerous ways, these systems are the most fascinating systems for research in microbial aquatic production ecology. Several PhDs and many Master students have graduated with RAS as the model system.

Previous activities have been funded by the European Commission and the Norwegian Research Counsel. Ongoing activities are related to cooperations with the SINTEF FHF MonMic-project, the SINTEF/LetSea RFF Lumpsucker in RAS-project, the Ecomarine/LetSea Salmon RAS biofilter-project and the NOFIMA QTRL AQUA-project.

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Production of biogas

Key words: Marine biomass, brown seaweeds, cattle manure, fiber fraction, organic fertilizer.

Biogas production from marine primary biomass consisting of brown seaweeds has been intensively studied in projects described above, see Biomass degradation.

Long-term cooperation with Bioskiva AS has handled a variety of aspects related to process optimalization of anaerobic fermentation of cattle manure for total utilization, in their concept with three commercial products biogas, Bioskiva plant cover from fiber fraction and organic (Debio approved) fertilizer from final liquid leftover fraction. The latter has been successfully stabilized as odour free. From 2009 we also participate in the NFR (BIP) project "Biogas Trøndelag" on biogas production by the newly formed company Biogass Fosen.

Related Master projects run in part at Sintef Biotechnology and Bioskiva AS.

SINTEF Aquaculture Technology

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For earlier research interests, see The archives.