Articulated coralline algae provide a spatial refuge to juvenile sea urchins from predatory crabs
Coralline algae provide settlement cues, food, and biotic structure for benthic marine invertebrates in intertidal and subtidal habitats. Here, we present evidence from laboratory experiments that juvenile sea urchins Strongylocentrotus droebachiensis (1.0–3.0 mm test diameter) are chemically attracted to articulated coralline algae Corallina vancouveriensis in the San Juan Archipelago (Washington, USA), resulting in movement of sea urchins into the algae. This behavior significantly reduced sea urchin mortality in the presence of predatory crabs Pagurus spp. and Cancer oregonensis as compared to treatments with no algae. In addition, we tested predation rates of various benthic predators from intertidal and subtidal habitats, and found that crabs were the most voracious predators of juvenile sea urchins. Our results indicate that C. vancouveriensis provides a spatial refuge to juvenile sea urchins from predatory crabs, and may facilitate recruitment into sea urchin populations by enhancing juvenile survival.
KeywordsHermit Crab Coralline Alga Test Diameter Benthic Marine Invertebrate Spatial Refuge
We thank K. Dobkowski, M. Dethier, and T. Mumford for assistance with the collection of experimental organisms, A. Summers for providing laboratory facilities for experiments with O. maculatus, M. Van de Brooke and J. Huie for laboratory assistance, and Friday Harbor Laboratories for facilities access and logistical support. J. Ching provided the illustration in Fig. 1b. T. Carrier, K. Filbee-Dexter and 2 anonymous reviewers provided helpful comments on the manuscript. DSY received funding from the Mary Gates Endowment. CJF was supported by a Friday Harbor Laboratories Postdoctoral Fellowship.
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Conflict of interest
The authors declare that they have no conflict of interest, that all animals have been sampled and treated according to national legislation, and that all required permissions have been obtained.
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