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 still unknown are the detection mechanism and the response to waves. Larvae may sense spatial velocity gradients (strain rate and vorticity) or acceleration. Larval-scale flows are affected differently by turbulence and waves; turbulence can generate larger strain rates and vorticity whereas 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.
Intellectual Merit: The proposed research addresses the following fundamental aspects of larval behavior and the ecological impacts of turbulence and waves: 1) Novel approaches to gain 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 scale of larvae. 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. 2) Impact of waves on behavior. Many habitats are influenced or even dominated by waves, yet no study to date has explored the potential for waves to provide a larval behavioral signal. This study will be the first to explore larval response to the large accelerations present only in waves. 3) 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 uncertainty in dispersal and recruitment. 4) 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 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 potential ecological impacts of changing physical processes on larval behavior and dispersal.
Broader Impacts: The proposed study integrates ecology, ocean physics, and state-of-the-art technology to promote interdisciplinary research, teaching, and infrastructure. Co-PI Gerbi is a postdoctoral associate, and his career will benefit from mentoring and experience on a highly interdisciplinary project. One graduate student will do dissertation research while gaining expertise in marine ecology, fluid mechanics, and flow-measurement technology. Two undergraduates will be recruited to participate through the NSF RIOS program and the Rutgers Aresty program for minority students, and the Rutgers student will do a senior thesis on part of this project. Results of this research will be incorporated into a new course in biological-physical interactions for graduate and undergraduate students. The project offers several opportunities to improve and expand the Larval Zoo, a web archive that provides movies of swimming larvae to a wide audience. The PIV and flow tanks will complete a new Plankton-Fluid Interactions Laboratory, leveraging a substantial contribution from Rutgers. The PIV is an invaluable upgrade to the flow-measurement capabilities of the Rutgers seawater flume facility.
