Meeting Abstract

P2.17  Monday, Jan. 5  Seagrass Epiphytes and Turbulence as Settlement Cues for Conch (Strombus alatus) Larvae SMITH, M.*; DAVIS, M.; WOLCOTT, T.G.; SHAWL, A.L.; N.C. State Univ., Raleigh; Harbor Branch Oceanographic Inst., Fort Pierce, FL; N.C.State Univ., Raleigh; Harbor Branch Oceanographic Inst., Fort Pierce, FL msmith@ncsu.edu

Knowledge of the mechanisms underlying larval dispersal and population connectivity of marine organisms is needed to predict ecosystem responses to global change, manage vital habitats, conserve threatened species, and manage fishery stocks. Recruitment in benthic invertebrate species with sedentary adults often depends on delivery of larvae to suitable habitats. Most larvae are not just passive particles, and the interactions of larval behavior and the local current regime play an important role in dispersal and settlement. Conch larvae respond to contact with benthic trophic cues by metamorphosing. We hypothesized that while planktonic, they also respond to water-borne cues and increased turbulence (symptomatic of shallower water) as indicators of potential nursery habitats. By swimming down or sinking, they increase their chances to explore the substrate and come in contact with metamorphic cues. Laboratory reared larvae competent to metamorphose responded to water-borne cues from epiphyte communities common on Thalassia testudinum blades by swimming faster, which would increase the frequency of contacts with the bottom. They also metamorphosed sooner than controls. Both phenomena would increase the probability of settling in suitable nursery habitats. When exposed to turbulence typical of shallow tidal flows, competent larvae, generally already low in the water column, showed no response. Pre-competent larvae, on the other hand, withdrew their velar lobes and sank. This would favor transport along or near the bottom and increase the probability of encountering suitable nursery habitats and settling there when competent.