Planktivorous feeding in calm and turbulent environments, with emphasis on copepods

Abstract

ABSTFUCT Turbulence may enhance contact rates between planktonic predators and their prey We formulate slmple and general models of prey encounter rates, taklng into account the behaviours and motility patterns of both prey and predator as well as turbulent fluld motlon Uslng these models we determine the levels of turbulence (as clmipation rate) at which ambient fluid motlon is lmportant in enhancing prey encounter rates for vanous types of predators (e g ambush and cruise predators, suspension feeders) Generally, turbulence has the largest effect on prey encounters for predators with low motility and long reactlon distances Also, turbulence is most important for meso-sized (mm to cm) predators and insignificant for smaller and larger predators The effect of turbulence on copepods is specifically examined For copepods that establish feeding currents, turbulence is of minor importance, for ambush feeding copepods, such as Acartldae and many cyclopoids, turbulence has a dominant influence on prey encounter rates The effect on cruising predators is intermediate Application of the models to situations examined experimentally demonstrates a hlgh predictive performance Finally we explore and model the potentially negatlve effects of turbulence on copepod feedlng currents, prey perception and capture success At typical and even high turbulent lntenslties none of these IS slgnificantly affected