Spatial and temporal variability in juvenile bivalve dispersal: effects of sediment transport and flow regime

Many species of benthic marine invertebrates, including bivalves, continue to disperse as juveniles (post-settlement). This dispersal has the potential to alter patterns set up at the time of settlement. Great spatial and temporal variability in rates of dispersal of juvenile bivalves has been observed in the field. We made synoptic measurements of current speeds and rates of bedload transport of sediment and dispersal of juvenile bivalves in the Navesink estuary, New Jersey, USA to examine the contribution of spatial and temporal variation in current speed to dispersal patterns. Daily rates of juvenile bivalve dispersal were high and varied strongly across sites. Bivalve dispersal was positively related to rates of sediment transport and current velocities, but not significantly to ambient density of bivalves. Variability in bivalve dispersal across dates was considerably less than that across sites, likely because tidal current speeds varied less by date than by site. The strong relationship between bivalve dispersal and sediment transport and velocity suggests that dispersal of the bivalve species in this estuary is initiated by sediment transport.