A theoretical comparison of the contributions of random swimming and turbulence to absolute dispersal in the sea

Mathematical models are used to evaluate the importance of random swimming to the diffusion of organisms in a turbulent medium. Criteria are developed to provide an objective means of determining when random swimming can be neglected, potentially reducing the model complexity and field research necessary to adequately address a given scenario. The models investigated indicate that horizontal random swimming does not contribute significantly to the displacement of oceanic larvae relative to their expected positions, but they do not rule out the importance of vertical random swimming. The models also show that horizontal swimming by larger pelagic organisms could easily dominate turbulence in the ocean and may be important to larvae in less turbulent bodies of water such as bays and lakes.