Turbulence and Seagrass Epiphytes as Settlement Cues for Conch (Strombus alatus)Larvae

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Title: Turbulence and Seagrass Epiphytes as Settlement Cues for Conch (Strombus alatus)Larvae
Author: Smith, Melanie
Advisors: Dr. Ping-tung Shaw, Committee Member
Dr. Daniel Kamykowski, Committee Member
Dr Thomas G. Wolcott, Committee Chair
Abstract: SMITH, MELANIE. Turbulence and Seagrass Epiphytes as Settlement Cues for Conch (Strombus alatus) Larvae. (Under the direction of Thomas G. Wolcott.) Knowledge of the mechanisms underlying larval settlement and recruitment of marine organisms is needed to manage fishery stocks, conserve threatened species, manage vital habitats and predict responses of populations, communities, and ecosystems to global change. Recruitment in benthic invertebrate species with sedentary adults often depends in part on settlement of larvae within 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 settlement patterns. Conch larvae respond to contact with benthic trophic cues in nursery habitats by metamorphosing. I 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 would increase their chances to explore the substrate and come in contact with metamorphic cues. When exposed to turbulence typical of shallow tidal flows, laboratory-reared larvae competent to metamorphose, 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. Competent larvae responded to water-borne cues from epiphyte communities common on Thalassia testudinum blades by swimming faster in all directions and exploring the cue source, which would increase the frequency of contacts with substrates within a habitat matrix. They also metamorphosed in response to the epiphyte cue. Both phenomena would increase the probability of settling in suitable nursery habitats.
Date: 2009-07-16
Degree: MS
Discipline: Marine, Earth and Atmospheric Sciences
URI: http://www.lib.ncsu.edu/resolver/1840.16/2662

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