Bridging the gap from ocean models to population dynamics of large marine predators: A model of mid-trophic functional groups

The modeling of mid-trophic organisms of the pelagic ecosystem is a critical step in linking the coupled physical–biogeochemical models to population dynamics of large pelagic predators. Here, we provide an example of a modeling approach with definitions of several pelagic mid-trophic functional groups. This application includes six different groups characterized by their vertical behavior, i.e., occurrence of diel migration between epipelagic, mesopelagic and bathypelagic layers. Parameterization of the dynamics of these components is based on a temperature-linked time development relationship. Estimated parameters of this relationship are close to those predicted by amodel based on a theoretical description of the allocation of metabolic energy at the cellular level, and that predicts a species metabolic rate in terms of its body mass and temperature. Then, a simple energy transfer fromprimaryproduction is used, justifiedby theexistence of constant slopes in log–log biomass size spectrum relationships. Recruitment, ageing,mortality and passive transportwith horizontal currents, taking into account vertical behavior of organisms, aremodeled by a systemof advection–diffusion-reaction equations. Temperature and currents averaged in each vertical layer are provided independently by anOceanGeneral CirculationModel and used to drive themid-trophic level (MTL)model. Simulationoutputs arepresented for the tropical PacificOcean to illustratehowdifferent temperature and oceanic circulation conditions result in spatial and temporal lags between regions of high primary production and regions of aggregation ofmid-trophic biomass. Predicted biomasses are compared against available data. Data requirements to evaluate outputs of these types ofmodels are discussed, aswell as the prospects that they offer both for ecosystem models of lower and upper trophic levels. 2009 Elsevier Ltd. All rights reserved.