Meeting Abstract
Some previous studies, though not all, have reported that the vertical distribution of bivalve larvae shifts upward in the water column on flood tides and downward on ebb tides. When observed, such shifts have been interpreted as reflecting the vertical migration of larvae (i.e., an active behavioral process). This interpretation assumes that tidally-driven vertical velocities are insignificant compared to larval swimming speeds, but that assumption may not be valid in all regions. We assessed the tidal vertical distribution of mussel (Mytilus edulis) larvae at 5 sites on 8 dates in the Gulf of Maine. We then used a high-resolution coastal circulation model to predict the vertical distribution of passive particles at one site on 4 sample dates. Finally, we conducted a multi-part meta-analysis of published papers on tidal and diel shifts to assess whether variation in the results among studies could be explained by tidal vertical advection via two proxies – tidal amplitude and shelf slope. Our results demonstrate the importance of considering passive processes when evaluating the role that vertical migration behaviors play in the movement of weakly swimming meroplankton.
