Theoretical Ecology Group

Institutt for biologi
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Group Leader, Professor, PhD
Øyvind Fiksen

Towards trait-based ecosystem models

I work on behaviour and strategies in fish, zooplankton and microbes, and on the consequences of these tactics and strategies in an ecosystem context. The aim is to develop ecological models where mass and energy fluxes are emerging from evolutionary consistent mechanisms - through natural selection.

The vertical dimension in aquatic ecosystems contain steep gradients in temperature, turbulence and light. Such environmental factors influence most organisms directly, and sets up trade-offs between growth and survival. Understanding these trade-offs, and how organisms respond to them are important not only for behavioural ecologists, but also for recruitment processes to fish populations and ecosystem functioning. As an example, both feeding success and death rates of a larval fish depends on its activity level and where in the water column it prefer to be (see illustration).

Behavioural flexibility is strong in fish and zooplankton, and the diversity of morphological and life-history traits are enormous in nature. Evolution provides us with a key to explain why some traits are successful in given environments. The challenge we have is to build ecological models where organisms are responsive, and at the same time account for mass-balance. In the project 'Trait-based ecosystem models' we are currently focusing on modelling the size-structure and vertical behaviour of the mesozooplankton community as an emergent property from environmental constraints and fish predation.

Fiksen Ø, Follows MJ, Aksnes DL. 2013.
Trait-based models of nutrient uptake in microbes extend the Michaelis-Menten framework
Reviews in Limnology and Oceanography. 58: 193-202. [ doi:10.4319/lo.2013.58.1.0193 ] [ pdf ]
Castellani M, Rosland R, Urtizberea A, Fiksen Ø. 2013.
A mass-balanced pelagic ecosystem model with size-structured behaviourally adaptive zooplankton and fish
Ecological Modelling. 251: 54-63. [ doi:10.1016/j.ecolmodel.2012.12.007 ] [ pdf ]
Visser AW, Fiksen Ø. 2013.
Optimal foraging in marine ecosystem models: selectivity, profitability and switching
Marine Ecology-Progress Series. 473: 91-101. [ doi:10.3354/meps10079 ] [ pdf ]


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