Meeting Abstract

8.5  Sunday, Jan. 4  Effects of benthic community topography on water flow, dispersal of chemical cues, and hydrodynamic stresses on settling larvae KOEHL, MAR*; CRIMALDI, JP; DOMBROSKI, DE; HADFIELD, MG; Univ. of California, Berkeley; Univ. of Colorado; Univ. of Colorado; Univ. of Hawaii cnidaria@socrates.berkeley.edu

Many bottom-dwelling marine animals disperse to new habitats via microscopic planktonic larvae. A critical step in recruitment of these larvae into benthic communities is settlement (landing and attaching to a surface). Flowing water can both deliver larvae to and dislodge newly settled larvae from surfaces. We used fouling communities that develop on docks to investigate how the fine-scale topography of a benthic community affects the nearby ambient water flow, and how that flow disperses chemical cues released by the community and hydrodynamic stresses on larvae settling into the community. Measurements of water flow along surfaces in Pearl Harbor, HI, showed that fouling communities are exposed to oscillatory flow (wind chop, ship wakes) superimposed on slow currents. We exposed fouled plates at different stages of community development to such flow regimes in a wave flume, used laser-Doppler velocimetry to measure water velocities 500μm from surfaces to determine instantaneous hydrodynamic stresses encountered by larvae settling onto different spots within each community, and calculated larval settlement probabilities. We also used simultaneous planar laser-induced fluorescence and particle image velocimetry to quantify fine-scale turbulent structure of the flow and the spatio-temporal patterns of odor dispersal above fouling communities. Community surface roughness increases turbulent transport of larvae and dispersal of chemical cues in the water, but provides flow microhabitats where hydrodynamic forces on settled larvae can be low. In turbulent flow, hydrodynamic stresses on settled larvae are episodic, and are higher if wind chop or ship wakes occur.