Numerical simulations of larval transport into a rip-channeled surf zone
Fujimura, Atsushi G.
Reniers, Ad J.H.M.
Paris, Claire B.
Shanks, Alan L.
MacMahan, Jamie H.
Morgan, Steven G.
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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.
The article of record as published may be located at http://dx.doi.org/10.4319/lo.2014.59.4.1434
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Fujimura, Atsushi G.; Reniers, Ad J.H.M.; Paris, Claire B.; Shanks, Alan L.; MacMahan, Jamie H.; Morgan, Steven G. (2017);Larvae of intertidal invertebrates need to cross the surf zone to settle in their adult habitat. Onshore transport of invertebrate larvae and detritus at a steep beach was simulated with a biophysical larval tracking ...
Shanks, Alan L.; MacMahan, Jamie; Morgan, Steven G.; M Reniers, Ad J.H.; Jarvis, Marley; Brown, Jenna; Fujimura, Atsushi; Griesemer, Chris (Inter-Research, 2015);Larvae of many intertidal species develop offshore and must cross the surf zone to complete their onshore migration to adult habitats. Depending on hydrodynamics, the surf zone may limit this migration, especially on ...
Morgan, Steven G.; Shanks, Alan L.; MacMahan, Jamie; Reniers, Ad J.H.M.; Griesemer, Chris D.; Jarvis, Marley; Fujimura, Atsushi G. (ASLO Association for the Sciences of Limnology and Oceanography, 2017-05-09);Surf zone hydrodynamics vary along shorelines potentially affecting the delivery of larvae and zooplankton subsidies to intertidal communities, and, hence, the intensity of postsettlement interactions, growth and reproduction ...