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Lagrangian tracer studies of larval dispersal
G.L. Hitchcock, W.S. Arnold, R. Wanninkhof, M.E. Frischer, Y.P. Sheng
University of Miami
g.hitchcock@miami.edu(Abstract received 05/12/2005 for session A)
ABSTRACT
Larval dispersal is a common feature in the life cycle of many benthic marine invertebrates. We have examined the dispersal characteristics of intentionally-released cohorts of recently-hatched larvae of the hard clam Mercenaria mercenaria in two coastal lagoons of the Indian River, Florida, USA. Both modeled and Lagrangian data (observations from dye and gas tracers and surface drifters) were used to track introduced larval cohorts from release to periods when the larvae were competent to settle. When modeled dispersal was compared to observed larval distribution in one of the lagoons, the fate of larvae predicted by a tracer model and by the distribution of sulfur hexafluoride (SF6) did not agree with that predicted by trajectories of subsurface drifters and by a particle trajectory model. Thus, Lagrangian data suggest that model predictions of larval dispersal must be interpreted with care. Additionally, components of larval dispersal observed in the field that were not adequately replicated in the model were the spread (diffusion) of larvae as they were advected through the lagoon and larval behavior. These aspects of dispersal have important consequences for spatial patterns of recruitment, and illustrate the utility of Lagrangian observations in studies of larval dispersal. Future Lagrangian experiments with modified drifters and fluorescent particles are planned to further resolve larval dispersal.
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2005 LAPCOD Meeting, Lerici, Italy, June 13-17, 2005