MEPS 385:189-204 (2009)  -  doi:10.3354/meps08043

Paradigm lost? Cross-shelf distributions of intertidal invertebrate larvae are unaffected by upwelling or downwelling

Alan L. Shanks1,*, R. Kipp Shearman2

1Oregon Institute of Marine Biology, University of Oregon, PO Box 5389, Charleston, Oregon 97420, USA
2College of Oceanic and Atmospheric Sciences, Oregon State University, 104 COAS Administration Building, Corvallis, Oregon 97331, USA

ABSTRACT: We tested the hypothesis that larvae of intertidal invertebrates are swept offshore during upwelling and shoreward during downwelling. During summer 2007, vertically stratified zooplankton samples and oceanographic data were collected at 7 stations located from 0.7 to 27 km from shore near Coos Bay, Oregon, USA. Half the sample dates (27 June and 14 August) were characterized by upwelling conditions (lines of constant temperature and salinity tilted upward, and a band of cold surface water was against the coast) and the other half (3 and 18 July) were characterized by downwelling or relaxation (lines of constant temperature and salinity were flat, and warm surface waters were in contact with the shore). We identified and staged larvae of Neotrypaea californiensis, Balanus glandula, B. nubilus, Chthamalus dalli, Pollicipes polymerus, and Semibalanus cariosus/B. crenatus and identified (to species or taxa level) Mytilus californianus, M. trossulus, Hiatella arctica, Dendraster excentricus, and pinnotherid and pagurid zoea. On all sample dates, all taxa and larval stages were rare in surface waters (0 to 10 m depth) and, with one exception (B. nubilus cyprids), were abundant at the 3 inshore stations (0.7 to 4.5 km offshore) and very rare or absent at seaward stations. The average distance offshore of all taxa and larval stages ranged from 0.9 to 4 km from shore and did not vary with upwelling and downwelling. Upwelling and downwelling had no effect on the cross-shelf distribution of the larvae of intertidal invertebrates; the hypothesis that upwelling carries larvae offshore and downwelling carries them back onshore was not supported.

KEY WORDS: Larval transport · Dispersal · Recruitment · Ekman · Barnacle · Mytilus · California Current

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Cite this article as: Shanks AL, Shearman RK (2009) Paradigm lost? Cross-shelf distributions of intertidal invertebrate larvae are unaffected by upwelling or downwelling. Mar Ecol Prog Ser 385:189-204

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