Project: Relative Influence of Turbulence and Waves on Larval Behavior

This study will investigate how snail larvae from distinct habitats respond to fluid mechanical cues in turbulence and surface gravity waves. Turbulence and waves are common features of coastal flows and may provide larvae with behavior cues that aid transport toward specific flow regimes or habitats. Turbulence induces some mollusk larvae to sink more frequently, but the detection mechanism and the response to waves are unknown. Larvae may sense spatial velocity gradients (strain rate and vorticity) or acceleration. Larvalscale flows are affected differently by turbulence and waves, because turbulence can generate larger strain rates and vorticity but waves can generate larger accelerations. Larvae that sense multiple flow characteristics may be able to distinguish between turbulence-dominated coastal embayments and wave-dominated regions of the continental shelf. In this study, larval behaviors will be quantified in several devices that generate steady strain rates and vorticity, simple acceleration, homogeneous turbulence, and complex flow with turbulence plus waves. Data will be used to develop stochastic models of larval behavior as a function of hydrodynamics and to test hypotheses about ecological and size-based controls on behavior.

The proposed research addresses several fundamental aspects of larval behavior and the ecological impacts of turbulence and waves:

• Novel approaches for insights on behavioral signaling: Two-phase infrared particle-image velocimetry techniques will be applied in multiple flow tanks to study effects of both turbulence and waves at the larval scale. Statistical protocols will be developed for converting behavior observations into empirical models, laying the groundwork for careful integration of more complex behaviors with physical circulation models. Results will identify the key fluid characteristics affecting behavior in species from intertidal and shelf habitats.
• Impact of waves on behavior: Many habitats are influenced or even dominated by waves, yet the potential for waves to provide a larval behavioral signal is unexplored. To our knowledge, this will be the first study of how larvae respond to the large accelerations present only in waves.
• Role of behavior in dispersal: Benthic recruitment variability arises partly from vagaries of dispersal that result from larval responses to the physical environment. Turbulence and waves vary spatially and also temporally due to stratification, water depth, tides, and winds. Small-scale symptoms of turbulence and waves could elicit larval behaviors that contribute to differences in dispersal trajectories. This study will describe larval responses to hydromechanical cues that ultimately could explain considerable uncertainty in dispersal and recruitment.
• Adaptation to physical environments: Shears and acceleration are potential behavior signals that could be enhanced or dampened by human impacts such as boating, shoreline modification, or increased storms. If behaviors are tuned to specific flow regimes, larvae may have difficulty adapting  to changing marine environments. This work will be instrumental in assessing the potential ecological impacts of changing physical processes on larval behavior and dispersal.

In addition to the data contributed to BCO-DMO, addtional data resources include:

1. Particle image velocimetry data: Metadata for digital image data will be archived on the project
web page hosted by Rutgers Institute of Marine and Coastal Sciences. Image data will be made
available on request after publication of results. The Rutgers library system is implementing a data
archiving system, and project metadata will also be stored on that system when it becomes available.

2. Biological Data: Adult snails will be collected from the intertidal zone and from the continental
shelf offshore of Tuckerton, New Jersey. Shelf samples will be collected by beam trawling from the
R/V Arabella. Two 1-day cruises will be scheduled in 2012 or later. Snails will be cultured and used
for spawning stock to produce larvae. Type specimens of all snails collected will be preserved in
ethanol and stored at Rutgers. Metadata for snail collections will be posted on the project web page.