A modelling study of developmental stage and environmental variability effects on copepod foraging

We used a stochastic Lagrangian model to study how behaviour contributes to copepod grazing success. The model simulates distinct foraging behaviours of Clausocalanus furcatus, Paracalanus aculeatus, and Oithona plumifera. Three sets of simulations were performed to investigate the effects of (a) prey-size preference; (b) variation in prey-size spectra; and (c) turbulence intensity on these species' grazing rates. The size preference simulations demonstrate that, compared with copepodites, mature females have cell ingestion rates that are an order of magnitude lower, while carbon uptake is reduced by 35%. A prey spectrum that is skewed towards cells <6 μm promotes copepodite success because the basal metabolic needs of the adult females require a prey concentration of 850-1000 cells ml. Variations in turbulence intensity reveal distinct ecological niches, with stronger mixing favouring O. plumifera and stable conditions favouring C. furcatus. Differences in theoretically derived and simulated prey-encounter rates demonstrate that the hopping behaviour of O. plumifera provides an order of magnitude increase in prey encounter, whereas the feeding behaviour of C. furcatus can result in localized depletion of prey. These simulations highlight the importance of species-specific feeding behaviour in defining oceanic copepod distributions. © 2008 International Council for the Exploration of the Sea. Published by Oxford Journals. All rights reserved.