Numerical simulations of larval transport into a rip-channeled surf zone
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Authors
Fujimura, Atsushi G.
Reniers, Ad J.H.M.
Paris, Claire B.
Shanks, Alan L.
MacMahan, Jamie H.
Morgan, Steven G.
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Advisors
Date of Issue
2014
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Abstract
Competent larvae of intertidal invertebrates have to migrate toward shore for settlement; however, their
migration through the surf zone is not understood. We investigated larval transport mechanisms at a ripchanneled
beach. Because tracking larvae in the surf zone is infeasible, we used a three-dimensional biophysical
model to simulate the processes. The coupled model consists of a physical module for currents and waves, and a
biological module for adding larval traits and behaviors as well as Stokes drift to Lagrangian particles. Model
calculations were performed with and without onshore wind forcing. Without wind, wave-driven onshore
streaming occurs in the bottom boundary layer outside the surf zone. With onshore wind, onshore currents occur
near the surface. In the surf zone, offshore-directed rip currents and compensating onshore-directed currents over
shoals are formed in both no-wind and wind cases. In the biological module, neutral, negative, and positive
buoyant particles were released offshore. Additionally, particles either sank in the presence of turbulence or not.
Two scenarios achieved successful onshore migration: Negatively buoyant larvae without wind forcing sink in the
turbulent bottom boundary layer and are carried onshore by streaming; positively buoyant larvae drift toward
shore in wind-driven surface currents to the surf zone, then sink in the turbulent surf zone and remain near the
bottom while transported shoreward. In both cases, the larval concentration is highest in the rip channel,
consistent with field data. This successful result is only obtained if turbulence-dependent sinking behavior and
Stokes drift are included in the transport of larvae.
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Article
Description
The article of record as published may be located at http://dx.doi.org/10.4319/lo.2014.59.4.1434
Series/Report No
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Oceanography
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This study is supported by National Science Foundation (NSF) Ocean Sciences (OCE-092735) ‘Collaborative Research: Does coupling between the inner shelf and surf zone regulate larval supply to intertidal populations?’ C. Paris is funded by NSF (OCE-1155698). This is a contribution of the Rosenstiel School of Marine and Atmospheric Science, the Oregon Institute of Marine Biology, the Naval Postgraduate School, and the Bodega Marine Laboratory.
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Citation
Limnol. Oceanogr., 59(4), 2014, 1434–1447
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This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.