Transport of larvae and detritus across the surf zone of a steep reflective pocket beach
Shanks, Alan L.
Morgan, Steven G.
M Reniers, Ad J.H.
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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.
The article of record as published may be found at http://dx.doi.org/10.3354/meps11223
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Persistent Differences in Horizontal Gradients in Phytoplankton Concentration Maintained by Surf Zone Hydrodynamics Shanks, Alan L.; Morgan, Steven G.; MacMahan, Jamie; Reniers, Ad J.H.M.; Jarvis, Marley; Brown, Jenna; Fujimura, Atsushi; Ziccarelli, Lisa; Griesemer, Chris (SpringerLink, 2017-06-21);Surf zones, regions of breaking waves, are at the interface between the shore and coastal ocean. Surf zone hydrodynamics may affect delivery of phytoplankton subsidies to the intertidal zone. Over a month of daily ...
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 ...
Shanks, Alan L.; Morgan, Steven G.; MacMahan, Jamie; Reniers, Ad J.H.M. (Ecological Society of America, 2017);Larvae in the coastal ocean are transported toward shore by a variety of mechanisms. Crossing the surf zone is the last step in a shoreward migration and surf zones may act as semipermeable barriers altering delivery of ...