MEPS 453:117-127 (2012)  -  DOI: https://doi.org/10.3354/meps09662

ABSTRACT: We exposed 4-arm plutei of the sea urchin Strongylocentrotus droebachiensis to 2 levels of turbulent dissipation rates (ε: 9 × 10⁻⁹ or 4 × 10⁻⁷ W kg⁻¹) in the laboratory, generated by using an oscillating metal grid. We compared direction of displacement and vertical velocities of larvae in turbulence with those of larvae in no flow and of passive particles in turbulence, for 2 different larval populations and over 2 trials. In turbulence, larval and passive particle movements were measured using particle image velocimetry, whereas larvae in no flow were filmed and their movements tracked digitally. Larvae in no flow and low turbulence tended to move towards the water surface, and this behaviour became more pronounced over time, suggesting that larvae became habituated to the turbulent flow. In high turbulence, larvae were unable to swim towards the surface of the water column and were consequently transported in secondary flows like passive particles. These levels of turbulence are likely to be encountered by larvae in near-shore coastal embayments or the surface layer of the continental shelf and will affect larval dispersal away from, or towards, parental habitats.

KEY WORDS: Turbulence · Larvae · Sea urchin · Swimming patterns · Turbulent dissipation rate · Weak swimmer · Benthic marine invertebrates · Angle of displacement · Batch effects