Turbulence impacts zooplankton fitness in opposing manners, by increasing contacts with prey but at the same time increasing contacts with predators.
Visser et al. (2009) investigate the fitness of individual zooplankton in terms of a trade-off between energetic gains and costs, and risk of predation. Through idealized descriptions of foraging and predation in a turbulent water column, they determine how fast a zooplankter should swim, if at all, and where should it position itself in the vertical to maximize its fitness given certain environmental conditions. Suspension feeding has an advantage over ambush feeding at high turbulence levels, whereas cruise feeding becomes optimal at low turbulence levels.
In general, behaviours that seek out low levels of turbulence increase an individual’s fitness, a prediction that runs counter to turbulent encounter rate arguments, and exposes the fallacy of examining only the foraging aspects of the fitness trade-off.
Figure: Optimal swimming speed v’ (mm/s) for a neutrally buoyant organism as a function of turbulent dissipation rate e (m2/s3) and (A) prey concentration P (m-3).
This study was supported by grants from the Danish Research Agency (272-07-0485, 21-03-0299, 3304-FFVFP -060683-01), and EUR-OCEANS NoE.
Visser, A.W.*, Patrizio Mariani* , Simone Pigolotti, 2009. Swimming in turbulence: zooplankton fitness in terms of foraging efficiency and predation risk, JOURNAL OF PLANKTON RESEARCH, Vol 31, No 2, pp121–133, http://dx.doi.org/10.1093/plankt/fbn109