Planktonic larvae 05 act like passive particles in turbulent near‐bottom flows1

The hypothesis that infaunal polychaete larvae ( Mediomastus ambiseta ) sink through the water like passive particles in turbulent near‐bottom flows was tested in the field with two geometrically different sediment traps. Laboratory flume experiments dictated the a priori prediction that larvae would be significantly overcollected by one trap design relative to the other. In field experiments, this a priori prediction was always supported. Thus, Mediomastus larvae may be distributed in near‐bottom waters according to the hydrodynamical processes governing the distribution of fine suspended sediments. Other processes that could have produced the patterns of larval collections between the trap designs now must be tested against the passive sinking hypothesis. Because the passive sinking hypothesis could not be falsified in these field experiments, considerations of hydrodynamical phenomena must be included in future studies of larval settlement. For example, larvae may first reach the seabed at sites where sediments with similar fall velocities would initially settle.