Lavelle

Integrating Ocean Circulation and Transport with Larval Studies at EPR 9-10ºN

J.W. Lavelle¹*, L. Mullineaux², D. McGillicuddy², A.Thurnherr³, & J. Ledwell²

Corresponding author: j.william.lavelle@noaa.gov
¹NOAA/Pacific Marine Environmental Laboratory, 7600 Sand Point Way NE Seattle, WA 98115 USA
²Woods Hole Oceanographic Institution, Woods Hole, MA 02543 USA
³Lamont Doherty Earth Observatory, Palisades, NY 10964 USA

Abstract:
LADDER (LArval Dispersal on the Deep East pacific Rise) has been a four-year effort encompassing field observations of currents, hydrography, turbulence, SF6 tracer dispersion, larval distributions and recruitment strategies, along with 2- and 3-d numerical models of local ocean circulation and larval transport. The goal has been to lay the foundation for and make initial inroads into understanding the connectivity of vent populations as mediated by larval dispersal between the hydrothermal oases that lie along the crest of this ridge segment. The field observations of currents, SF6 dispersion, and the 3-d model of flow together indicate the importance of along-ridge flank current jets and the Lamont seamount chain in passive material (e.g. larvae of many important species, SF6) dispersion. The larval field studies and the 2-d model of larval transport along an idealized ridge show the importance of the jets to larval transport and provide evidence that contradicts the idea that strong cross-ridge flow means that larvae will be advected far off axis. Probabilities for larvae to be over vent areas at the time of settlement strongly depends on plankton behavioral characteristics (balloonist vs demersal), as well as the duration of the precompetency period. Our work integrates ocean physics with biology and observations with numerical models.

Keywords:
Larval transport, ocean circulation, numerical models, water-column data, SF6 tracer dispersion

Contributions to Integration and Synthesis:
The observational and modeling technology employed in this work could be used to describe water-column transport of hydrothermal material and vent larvae at other ISS sites (given suitable, available or new data). The model could be extended to include settling particles to look at transport and deposition of hydrothermal constituents off ridge and into sediments. SF6 tracer could be used to seed buoyant plumes and look at regional hydrothermal fluid dispersion and water-column mixing. The numerical model could conceivably be used to connect water-column anomaly data of a hydrothermal tracer with vent fluxes, though the first assessment must be how the sparsity in samples and the uncertainty of anomaly measurements propagate into source-flux uncertainty.