The quick and the dead: Larval mortality due to turbulent tidal transport

Marine populations are typically connected over greater spatial scales than their terrestrial counterparts due to many species having a highly dispersive, planktonic larval phase. However, high levels of larval mortality in the plankton may reduce connectivity between populations. The effect of turbulence on larval mortality was investigated under natural conditions in a field experiment. Larvae were collected before and after being subjected to turbulent tidal flow from a marine reserve, with differential mortality being observed between taxa. Thin-shelled veligers of gastropods and bivalves showed significantly increased mortality, while barnacle nauplii and cyprids, bryozoan cyphonaute larvae and polychaete trochophores showed no effect of turbulent tidal transport. Where appropriate, marine reserve design should account for the reduced connectivity between populations associated with turbulent tidal transport between reserve and adjacent areas.