Alongshore variation in barnacle populations is determined by surf zone hydrodynamics
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Authors
Shanks, Alan L.
Morgan, Steven G.
MacMahan, Jamie
Reniers, Ad J.H.M.
Subjects
Balanus
Chthamalus
larval recruitment
larval settlement
latitudinal variation
rip current
surf zone hydrodynamics
upwelling
Chthamalus
larval recruitment
larval settlement
latitudinal variation
rip current
surf zone hydrodynamics
upwelling
Advisors
Date of Issue
2017
Date
Publisher
Ecological Society of America
Language
Abstract
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 larvae to the shore. We related variation
in the structure of intertidal barnacle populations to surf zone width (surf zone hydrodynamics
proxy), wave height, alongshore wind stress (upwelling proxy), solar radiation, and latitude at
40 rocky intertidal sites from San Diego, California to the Olympic Peninsula, Washington. We
measured daily settlement and weekly recruitment of barnacles at selected sites and related
these measures to surf zone width. Chthamalus density varied inversely with that of Balanus,
and the density of Balanus and new recruits was negatively related to solar radiation. Across
the region, long-term mean wave height and an indicator of upwelling intensity and frequency
did not explain variation in Balanus or new recruit densities. Balanus and new recruit densities,
daily settlement, and weekly recruitment were up to three orders of magnitude higher at sites
with wide (>50 m), more dissipative surf zones with bathymetric rip currents than at sites with
narrow (<50 m) more reflective surf zones. Surf zone width explained 30–50% of the variability
in Balanus and new recruit densities. We sampled a subset of sites <5 km apart where coastal
hydrodynamics such as upwelling should be very similar. At paired sites with similar surf zone
widths, Balanus densities were not different. If surf zone widths at paired sites were dissimilar,
Balanus densities, daily settlement, and weekly recruitment were significantly higher at sites
with the wider, more dissipative surf zone. The primary drivers of surf zone hydrodynamics are
the wave climate and the slope of the shore and these persist over time; therefore site-specific
stability in surf zone hydrodynamics should result in stable barnacle population characteristics.
Variations in surf zone hydrodynamics appear to play a fundamental role in regulating
barnacle populations along the open coast, which, in turn, may have consequences for the
entire intertidal community.
Type
Article
Description
The article of record as published may be found at http://doi.org/10.1002/ecm.1265
Series/Report No
Department
Oceanography
Organization
Identifiers
NPS Report Number
Sponsors
National Science Foundation
Funder
NSF-OCE#092735
Format
25 p.
Citation
Alan l. Shanks, Steven G. Morgan, Jamie MacMahan, AD J. H. M. Reniers "Alongshore variation in barnacle populations is determined by surf zone hydrodynamics." Ecological Monographs, 87(3), 2017, pp. 508–532
Distribution Statement
Rights
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.