The group focuses on trophodynamic interactions within pelagic food webs ranging from:

• Primary producers at the base of the food web (phytoplankton)
• Secondary consumers (micro- and mesozooplankton e.g. heterotroph protists, gelatinous zooplankton, meroplankton)
• Tertiary consumers (meso-, macro- and megazooplankton e.g. ichthyoplankton, gelatinous zooplankton, meroplankton)

External and internal drivers

Pelagic food webs are considered as highly complex with a variety of feeding interactions, spatio-temporal dynamics and functional traits. We use field and experimental approaches to assess the role of:

1. External drivers (e.g. nutrients, temperature, light, hydrography) on trophodynamic interactions, functional traits and diversity
2. Internal drivers (intra- and inter-specific interactions) on shaping pelagic community structure and food web interactions.

The role of micrograzers (20-200 µm) as a trophic link between microbial and classical food webs are a special focus area. We analyse communities of small-sized protozoa (e.g. heterotrophic dinoflagellates, ciliates) and metazoa (e.g. meroplanktonic larvae, nauplii) focussing on the ability of micrograzers to (1) buffer nutritional imbalances at the base of the food web, (2) suppress and modulate phytoplankton blooms and (3) improve the food quality for secondary consumers are central aspects of our research. Here, multi-trophic approaches are used to analyse food quantity and quality aspects within planktonic food-webs and interactions between micrograzers and larger zooplankton e.g. early life stages of fish larvae. The functioning of micrograzers with regard to trophic transfer efficiencies and alterations in energy transfer to higher trophic levels are considered in detail.

Core topics of research activities

Large-scale mesocosm experiment at the MEDIMEER facility

(MEDIterranean platform for Marine Ecosystem Experimental Research), CNRS, Sète (France).

Our participation is funded via the AQUACOSM Transnational Access, an EU network of mesocosm facilities for research on freshwater and marine ecosystems open for global collaborations. Within this framework, Katharina Bading (PhD candidate at NTNU, Department of biology) and Nicole Aberle-Malzahn participate in the WARMPlank mesocosm experiment studying the impact of global warming on Mediterranean plankton communities.

Other research activities/topics

• Climate change impacts (global warming, ocean acidification) on pelagic communities in low and high latitude regions
• Impact of external stressors (e.g. changes in temperature, pH, salinity, light or nutrients) on match-mismatch situations in the plankton
• Alterations in microplankton community structure and potential consequences for trophic transfer efficiencies up the food web
• Bloom formation and phenology patterns of key zooplankton groups (microzooplankton, ichthyoplankton, jellyfish)

The methodological approaches range from field observations to small- or large-scale experimental approaches using e.g. mesocosm set-ups in order to simulate future ocean conditions (warming, oacean acidification). The aim is to create near-natural conditions by using e.g. natural plankton communities and applying different stressors to the system (e.g. changes in temperature, pH, salinity, light or nutrients).

The Nansen Legacy Project

The Nansen Legacy Project (website in Norwegian) is funded by the Research Council of Norway (NFR). The project is a join effort of the Norwegian Arctic research community to establish a holistic understanding of a changing marine Arctic climate and ecosystem. Our emphasis is on trophic transfer and nutritional variations at the primary producer-consumer interface of Barents Sea plankton communities, an activity that is embedded into RF3 (‘The living Barents Sea’) focussing on biodiversity, ecosystem functioning and environmental forcing of the northern and central Barents Sea (Arctic-influenced) as opposed to the southern region (Atlantic-influenced). Here we aim at elucidating the role of nutritional variations in the diets of planktonic consumers in the Barents Sea ecosystem. The focus is on microzooplankton-mesozooplankton interactions and the trophic link between primary producers and consumers.

The MOSAiC expedition

125 years since Fridtjof Nansen conducted his 1.5-years long polar expedition with the boat FRAM, a huge international campaign started in September 2019 started on the same drift route to find new knowledge and create a better understanding on the impact of a changing climate on the Arctic ecosystem. The MOSAiC expedition (Multidisciplinary Operational Observatory for the Study of Arctic Climate) is a collaborative project involving many countries and hundreds of researchers. The ship was frozen into the ice and currently drifts within the ice over the Arctic Ocean. The purpose is to make continuous observations and gather data on how drift ice, sea and atmosphere are linked throughout the seasons. The world lacks such observations to gain a full understanding of how polar regions are affected by changes in the global climate. It is expected that MOSAiC will answer many unresolved questions in climate research and define a new scientific basis for Arctic climate research. Within MOSAiC we contribute to a better understanding on how climate change affects plankton communities in the Arctic and contribute to the NFR-funded project HAVOC with emphasis on sea ice pressure ridges and the biota within and underneath ridges.

Media

Six years into the ice - and beyong (Gemini 26.09.2019)

A day in the life of a jellyfish hunter (Gemini 11.10.2018)