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Marine Ecology Progress Series

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MEPS 582:33-43 (2017)  -  DOI:

Numerical simulations of onshore transport of larvae and detritus to a steep pocket beach

Atsushi G. Fujimura1,2,*, Ad J. H. M. Reniers2,3, Claire B. Paris2, Alan L. Shanks4, Jamie H. MacMahan5, Steven G. Morgan6

1Marine Laboratory, University of Guam, Mangilao, Guam 96923, USA
2Rosenstiel School of Marine and Atmospheric Science, University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149, USA
3Department of Hydraulic Engineering, Delft University of Technology, Stevinweg 1, 2628 CN, Delft, The Netherlands
4Oregon Institute of Marine Biology, University of Oregon, 63466 Boat Basin Road, Charleston, OR 97420, USA
5Department of Oceanography, Naval Postgraduate School, 1 University Way, Monterey, CA 93943, USA
6Bodega Marine Laboratory, University of California, Davis, 2099 Westside Road, Bodega Bay, CA 94923, USA
*Corresponding author:

ABSTRACT: 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 model. Hydrodynamic model calculations were performed for 24 h after a 24 h spin-up stage with bathymetry and averaged wave data obtained during the summer of 2011 at Carmel River State Beach, California, and with and without onshore wind. The physical model output was then transferred to a Lagrangian larval tracking model using several types of particles representing larvae. A southward alongshore current controlled particle distribution in the middle and north of the domain. At the southern shore, negatively buoyant particles were trapped by eddies generated between the alongshore current and shore, while positively buoyant particles were carried onshore by wind-driven surface currents. The concentration of modeled detritus in the surf zone was positively correlated with that of negatively buoyant larvae. Additionally, the concentrations of detritus and competent larvae within the surf zone were negatively correlated with wave height, consistent with the observations of the accompanying field study. Some eddies contributed to forming high particle concentration patches by trapping them in the surf zone. More small eddies were generated closer to the shore with smaller waves, leading to high larval and detrital concentration in the surf zone. As waves increased in size, fewer and larger eddies formed, predominantly outside the surf zone, and consequently fewer larvae and detritus particles entered or stayed in the surf zone.

KEY WORDS: Larval transport · Biophysical model · Surf zone · Steep beach · Competent larvae · Detritus · Eddies

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Cite this article as: Fujimura AG, Reniers AJHM, Paris CB, Shanks AL, MacMahan JH, Morgan SG (2017) Numerical simulations of onshore transport of larvae and detritus to a steep pocket beach. Mar Ecol Prog Ser 582:33-43.

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