In situ Habitat Selection by Settling Larvae of Marine Soft-Sediment Invertebrates

To test whether larval selectivity at settlement contributes to distributional patterns of benthic infauna, we conducted three reciprocal sediment transplant experiments at 15-m-deep coarse-sand and muddy-sand sites (∼3 km apart) on the continental shelf near Tuckerton, New Jersey. During 3- to 5-d deployments in 1994, larvae of the surfclam, Spisula solidissima, selected coarse sand over muddy sand, and capitellid polychaetes selected muddy sand over coarse sand, regardless of site. Thus, larvae of both taxa selected sediments typical of adult habitats, displaying selectivity consistent with previous flume experiments. Settlement intensity changed significantly over the ∼6-week period during which experiments were conducted. Several other taxa exhibited selectivity consistent with field distributions, and several were nonselective. Significant site differences in settlement intensity were also observed on some dates for several taxa. Plankton pump samples taken at the sites during tray experiments suggested that significant differences in supply of surfclam larvae over the 3-km scale contributed to between-site differences in settlement. In the later experiments, surfclams in experimental trays were larger than would be expected for recent settlers, suggesting that postsettlement migration and selectivity occurred on small scales. These experiments demonstrate that differences in larval supply over scales of kilometers and time scales of weeks can affect settlement intensity but that habitat selection by settling larvae of some species of soft-sediment invertebrates may set initial distribution patterns.