Date of Award

Summer 8-31-2017

Document Type

Thesis

Degree Name

MS Marine Science

Department

Environmental and Ocean Sciences

Committee Chair

Nathalie B. Reyns

Committee Member

Jennifer C. Prairie

Committee Member

Jesús Pineda

Abstract

Many marine organisms begin their lives as tiny larvae that are at the mercy of ocean currents. Understanding the transport and subsequent dispersal of larvae is crucial, as it drives population connectivity in the ocean. Larval transport is a complex process involving both physical motions of the water and larval behavior. Vertical positioning is especially important because currents vary throughout the water column, and larvae at different depths will be advected differently. With swimming speeds insufficient to swim against currents, marine larvae can mediate cross-shore transport by controlling their depth distributions. Thus, the overall objective of this study was to characterize the cross-shore and vertical distributions of barnacle larvae in La Jolla, southern California during a two-year period. The sampling design for this research included repeated larval collections in 2-m depth intervals spanning the entire water column at five cross-shore stations located in the nearshore between ~200 to 1000 meters from the rocky intertidal, adult barnacle habitat. Larval distributions were compared to hydrographic factors, including the mid-depth of the thermocline, thermal stratification, current velocities, and wave height, in an attempt to discern biological-physical mechanisms of larval transport. Despite seasonal and annual hydrodynamic variability, vertical and cross-shore distribution patterns of barnacle larvae remained consistent: nauplii were distributed farther from shore and cyprids were constrained nearshore when thermal stratification was high. These results support the inference that behavior is substantial in facilitating transport during pelagic larval stages, and leads to the hypothesis that stratification elicits enhanced behavioral control of barnacle cyprid larvae to remain close to shore and reach their adult habitat.

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