title: Surfzone hydrodynamics as a key determinant of spatial variation in rocky intertidal communities.
abstract: Larvae of intertidal species develop at sea and must return to adult habitats to replenish populations. Similarly, nutrients, detritus and plankton provide important subsidies spurring growth and reproduction of macroalgae and filter-feeding invertebrates that form the foundation of intertidal communities. Together, these factors determine the density and intensity of interactions among community members. We hypothesized that spatial variation in surfzone hydrodynamics affects the delivery of plankton subsidies. We compared entire zooplankton communities inside and outside the surf zone daily while monitoring physical conditions for one month each at two shores with different surfzone characteristics. Opposite cross-shore distributions of larvae and other zooplankters occurred at the two sites: zooplankton was much more abundant inside the mildly sloping dissipative surf zone (DSZ) with rip currents and was more abundant outside the steep reflective surf zone (RSZ). Biophysical numerical simulations demonstrated that zooplankters were concentrated in rip channels of the DSZ and were mostly unable to enter the RSZ, indicating the hydrodynamic processes behind the observed spatial variation of zooplankters in the surf zone. Differences in the concentration of larvae and other zooplankters between the inner shelf and surf zone may be an underappreciated, key determinant of spatial variation in inshore communities.
authors.affiliation: Bodega Marine Laboratory, University of California Davis, 2099 Westside Drive, Bodega Bay, CA 94923-0247, USA Department of Environmental Science and Policy, University of California Davis, 1 Shields Avenue, Davis, CA 93510, USA sgmorgan@ucdavis.edu.
authors.forename: Steven G
authors.identifier: 0000-0002-9971-5414
authors.initials: SG
authors.lastname: Morgan
authors.affiliation: Oregon Institute of Marine Biology, University of Oregon, PO Box 5389, Charleston, OR 97420, USA.
authors.forename: Alan L
authors.initials: AL
authors.lastname: Shanks
authors.affiliation: Marine Biophysics Unit, Okinawa Institute of Science and Technology, 1919-1 Tancha, Onna-son, Okinawa 904-0495, Japan.
authors.forename: Atsushi G
authors.initials: AG
authors.lastname: Fujimura
authors.affiliation: Delft University of Technology, Civil Engineering and Geosciences, Stevinweg 1, 2628CN Delft, The Netherlands.
authors.forename: Ad J H M
authors.initials: AJ
authors.lastname: Reniers
authors.affiliation: Department of Oceanography, Graduate School of Engineering and Applied Sciences, Monterey, CA 93943, USA.
authors.forename: Jamie
authors.initials: J
authors.lastname: MacMahan
authors.affiliation: Bodega Marine Laboratory, University of California Davis, 2099 Westside Drive, Bodega Bay, CA 94923-0247, USA.
authors.forename: Chris D
authors.initials: CD
authors.lastname: Griesemer
authors.affiliation: Oregon Institute of Marine Biology, University of Oregon, PO Box 5389, Charleston, OR 97420, USA.
authors.forename: Marley
authors.initials: M
authors.lastname: Jarvis
authors.affiliation: Department of Oceanography, Graduate School of Engineering and Applied Sciences, Monterey, CA 93943, USA.
authors.forename: Jenna
authors.initials: J
authors.lastname: Brown
mesh_terms: D000818:Animals; D017753:Ecosystem; D020387:Food Chain; D057446:Hydrodynamics; D007448:Invertebrates; D007814:Larva; D009792:Oceans and Seas; D010933:Plankton; D012624:Seaweed; D062206:Spatial Analysis; D014872:Water Movements
keywords: communities; hydrodynamics; larval recruitment; subsidies; surf zone; zooplankton