Meeting Abstract

S3.7  Monday, Jan. 4  Hydrodynamics of larval settlement from a larva’s point of view KOEHL, M.*; HADFIELD, M.; Univ. of California, Berkeley; Univ. of Hawaii cnidaria@berkeley.edu

Many benthic marine animals release larvae that are dispersed by ocean currents. These larvae swim and respond behaviorally to environmental factors such as light, shear, or chemical cues. However, larvae are so small (~0.01-1mm) that their trajectories are the vector sum of their behaviors and the motion of the water in which they are riding. We focus on settlement (landing and attaching to a surface), the first step in recruitment of larvae into benthic communities, to study how ambient water flow and larval behavior interact to determine where larvae land and where they stick to the substratum. Using coral reefs and fouling communities as study systems, we measure the turbulent, wavy water flow across them in the field and recreate it in wave-flumes where we can measure on the scale experienced by larvae (mm’s and ms’s) the instantaneous water velocities and the concentrations of odors released by the benthos. We use these data to determine the temporal pattern of velocities, shears, and odor concentrations encountered by settling larvae. On the scale of big organisms (cm’s – m’s), turbulent water flow across a rough substratum is well characterized by boundary shear velocity, and dispersal of dissolved substances is modeled as a diffusing cloud. However, examination of these processes on the scale encountered by an individual microscopic larva reveals a more complex and variable world. For example, larvae have rapid on-off encounters with chemical cues while swimming through fine filaments of odor swirling in unscented water. After they land they experience rapidly fluctuating hydrodynamic forces with peaks that depend on their location within the fine-scale habitat topography. We use individual-based models of rapid larval responses to spatially and temporally varying water flow to explore how behavior can affect where larvae settle.