MEPS 528:71-86 (2015)  -  DOI: https://doi.org/10.3354/meps11223

Transport of larvae and detritus across the surf zone of a steep reflective pocket beach

Alan L. Shanks1,*, Jamie MacMahan2, Steven G. Morgan3, Ad J. H. M Reniers4, Marley Jarvis1, Jenna Brown2, Atsushi Fujimura4, Chris Griesemer

1Oregon Institute of Marine Biology, University of Oregon, PO Box 5389, Charleston, Oregon 97420, USA
2Department of Oceanography, Naval Postgraduate School, 327c Spanagel Hall, Monterey, California 93943, USA
3Bodega Marine Laboratory, Department of Environmental Science and Policy, University of California Davis, 2099 Westside Dr., Bodega Bay, California 94923-0247, USA
4Department of Hydraulic Engineering, Delft University of Technology, Civil Engineering and Geosciences, Stevinweg 1, 2628CN Delft, The Netherlands
*Corresponding author:

ABSTRACT: 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 reflective rocky shores. As a logistically tractable analog of a rocky shore environment, we carried out a comprehensive biological and physical study of the hydrodynamics of a steep reflective sandy beach. Holoplankton and precompetent larval invertebrates were much less abundant within the surf zone than offshore, and their concentrations inside and outside the surf zone were not significantly correlated, suggesting that they were not entering the surf zone. Persistent offshore flow throughout the water column at the outer edge of the surf zone may prevent these organisms from entering the surf zone. In contrast, the concentrations of detritus and a competent larval invertebrate (i.e. cyprids), while also not significantly correlated with concentrations offshore, were frequently more concentrated in the surf zone than offshore. Within the surf zone, the concentration of detritus was significantly correlated with concentrations of competent larval invertebrates (barnacles, gastropods, polychaetes, and bopyrid amphipod) and organisms that may be associated with detritus (amphipods and harpacticoid copepods). These concentrations were significantly negatively correlated with average daily wave height. We hypothesize that detritus and larvae enter the surf zone near the bottom during calm wave conditions by a process of near-bottom streaming. Near-bottom streaming is associated with all surf zones and may be a general mechanism for onshore transport of larvae close to the coast.


KEY WORDS: Streaming · Cyprids · Competent larvae · Precompetent larvae · Detritus · Reflective beach · Cross-shore exchange


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Cite this article as: Shanks AL, MacMahan J, Morgan SG, Reniers AJHM and others (2015) Transport of larvae and detritus across the surf zone of a steep reflective pocket beach. Mar Ecol Prog Ser 528:71-86. https://doi.org/10.3354/meps11223

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