The influence of search strategies and homogeneous isotropic turbulence on planktonic contact rates

¹  Institute for Mathematical Sciences, Imperial College London - 53 Prince's Gate, Exhibition Road, South Kensington, London, SW7 2PG, UK
²  Rothamstead Research - Harpenden, Hertfordshire, AL5 2JQ, UK

Corresponding author: c.rhodes@imperial.ac.uk

Received: 4 August 2007
Accepted: 15 October 2007

Abstract

Many species have been shown to adopt a Lévy-flight pattern of movement which are consistent with the most efficient way to locate sparsely distributed targets. Here, we consider a predator that conducts its search for prey in a turbulent environment. Such a situation is relevant to zooplankton-phytoplankton ecosystems. Kinematic simulation is used to represent the turbulent velocity field in the surface layers of the open ocean and contact with the prey is maximised for a predator swimming a Lévy flight with an exponent 1.2. The contact rate exceeds that recorded during straight-line swimming and passive advection. The observation that the contact rate is maximised for 1.2 appears to be not strongly dependent on predator swimming speed. The results are discussed in the context of recent work on planktonic search in laboratory conditions where Lévy-flight exponents of 2 were noted.