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Dynamics of ocean primary productivity

Oceanic photosynthesis contributes roughly half of the earth’s net primary production. However, there are large geographical variations, ranging from the oligotrophic subtropical gyres to highly productive upwelling and coastal systems.

The ocean productivity is governed by the physical environmental forcing and chemical and biological mechanisms and these occur on vastly different scales. A major challenge is how to simultaneously and realistically account for the mortality, growth and competitive processes at the scale of the microbial organisms (µm) to the hydrodynamic processes, which transports nutrients into the euphotic zone, at spatial scales of meters to thousands of km. The Hjort Centre will work towards advancing our understanding of how climate, ocean physics and biogeochemistry influence marine productivity by use of both field- and modelling studies. This knowledge will be used towards predicting how ocean productivity responds to climate variability

Relevant projects involving Hjort Centre members

VIMPACT: Estimating viral impact and cost of resistance on marine phytoplankton communities
Project leader: António Pagarete, PhD, Department of Biology, University of Bergen
Funding source: RCN (HAVKYST)
Period: 2014-2017
In collaboration with: Station Biologique de Roscoff, France; Plymouth Marine Laboratory, UK; Leicester University, UK

Numbering in excess of 10 million per ml of seawater it is now well acknowledged that viruses are interacting with their cellular counterparts in the microbial kingdom on an unforeseen scale. Notably, viral lubrication of the ocean's microbial machinery is a critical regulator of vertical carbon transport in marine food webs. Although still poorly understood, we now know that the way viruses interact with and shape marine microbial communities has enormous implications for global biogeochemical cycling and ecosystem function. Two decades of continuous efforts in our group to conceptualize this viral impact have led to the Killing the Winner (KtW) model, recognized as the most accurate representation of cell-virus interactions in the planktonic realm. Particularly, by differentiating viral impact on microbial hosts with different growth and immunity capacities, KtW explains the fundamental importance of viruses for the existence of highly dynamic and diverse microbial communities. This model can be an important tool for our understanding and management of marine ecosystems. In that sense, it is indispensable an empirical derivation of its variables and evaluation of its predictions. With VIMPACT we will: 1) confront the theoretical assumptions of KtW with empirically derived values for its key parameters, 2) evaluate KtW predictions at increasing complexity levels, from strain to natural phytoplankton communities, and 3) reassess and improve the currently existing model in light of the empirically-driven results.