Meeting Abstract

81.1  Sunday, Jan. 6  Behavior and adhesion of settling marine larvae in turbulent pulses of water flow KOEHL, M.A.R.; Univ. of California, Berkeley cnidaria@berkeley.edu

Many benthic marine animals produce microscopic larvae that are dispersed by ocean currents. These larvae can only recruit into new habitats on which they have landed if they can resist being washed away by ambient water flow. The adhesive strengths of microscopic organisms such as larvae are typically measured by exposing them to steady flows of different velocities to determine the boundary shear stress at which they are dislodged from a surface. However, our field and flume measurements of water velocities at the scale of larvae on surfaces in different microhabitats within rugose benthic communities (coral reefs, fouling communities) revealed that larvae are exposed to brief pulses of rapid flow as turbulent eddies and waves sweep across the substratum. I used a picospritzer to subject settling larvae of byrozoans, tube worms, and sea slugs to realistic pulses of moving water to measure their adhesive strength under more natural flow conditions, and to determine how such fluctuating flow affected their behavior. I found that the response of a larva to a pulse of flow depended on larval behavior at the time the pulse hit, and on the larva’s recent history of exposure to flow pulses. Crawling larvae were more likely to be blown away than stationary larvae, and larval adhesive strength usually increased with duration of attachment to a surface. Larval “glues” that acted like viscous fluids when larvae were sheared off surfaces in steady flow behaved like elastic bungee cords when larvae were exposed to brief pulses of rapid flow. Therefore, to determine how ambient water motion affects the ability of settling larvae to recruit into benthic communities, we must measure larval responses to flow that varies on the rapid temporal scales encountered by the larvae in natural habitats.