Project: Collaborative Research: Linking behavior and transport of larvae using waves and turbulence as cues

NSF Abstract:
Many bottom-dwelling marine species have larvae whose behavior in the water column impacts dispersal and adult distributions. Snail larvae swim up with more effort or sink in response to cues from waves and turbulence, and it remains unclear whether larvae can use these physical cues for retention within or navigation among habitats. Larvae that swim up under waves may be retained over the continental shelf by wave-induced shoreward drift in surface waters. However, ocean warming causes larvae to be released earlier in spring when waves are larger and coastal upwelling is weaker, potentially carrying larvae into shallower waters that exceed the adults' temperature tolerance. The investigators will use a physical model of the Middle Atlantic Bight and adjacent estuaries to test hypotheses about how waves and turbulence affect transport patterns, retention near adult habitats, and climate-induced shifts in adult distributions. The project will produce simulations of ocean circulation and larval tracking codes that include waves both as behavior cues and as a transport mechanism; these products will be made publicly available. A graduate student will do a related dissertation. Undergraduate students will be involved through an NSF-funded REU program, the Aresty Program, which engages Rutgers' diverse undergraduates in research to boost retention in STEM majors, the Rutgers Research in Science and Engineering program, which targets underrepresented minorities, and the Skidmore Summer Research program. Model outputs will be used to develop learning materials for undergraduates, packaged as a case study for distribution through the National Center for Case Study Teaching in Science. Research results will also be presented to adult (55 and over) learners through the Skidmore Encore lecture series.

Waves are unique in providing planktonic larvae with a behavior cue directly tied to a horizontal transport mechanism, and newly discovered larval responses to waves could have counter-intuitive impacts on larval transport and species distributions. Wave climates differ in the adjacent habitats of two congeneric snails: Tritia obsoleta occupies turbulent inlets and estuaries where waves are small, while Tritia trivittata occupies the continental shelf where waves are much larger. These two species' larvae sense waves and turbulence separately as acceleration and vorticity-induced body rotation, respectively. Late-stage estuarine larvae mainly exhibit turbulence-induced sinking that could reduce transport out of inlets and estuaries, whereas shelf larvae also exhibit wave-induced upward swimming that could aid retention over the shelf via Stokes drift. Since the 1960s, the shelf species' range has shifted into warmer water, opposite to predictions based on thermal tolerance. This shift may be driven by wave-induced larval transport; as ocean warming induces earlier spawning, larvae will encounter larger waves and weaker upwelling in spring, intensifying Stokes drift and onshore transport toward warmer, shallower waters of the inner shelf. The project will use numerical models to test hypotheses linking flow-induced larval behaviors to transport pathways, local retention, and climate-driven range shifts. Waves will be included as a source of both behavior cues and advection through acceleration and Stokes drift, respectively. Results will help resolve uncertainties about how Stokes drift, Eulerian return flow, and upwelling interact to transport larvae. Numerical experiments will describe how climate-driven changes in spawning phenology affect larval transport, potentially identifying the mechanism behind perplexing range shifts of shelf species into warmer water.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.