Design considerations for an artificial reef to grow giant kelp (Macrocystis pyrifera) in Southern California

As mitigation for estimated losses of kelp bed resources owing to the operation of the San Onofre Nuclear Generating Station (SONGS), Southern California Edison is building a 61 ha artificial reef to restore populations of the giant kelp, (Macrocystis pyrifera). This reef is unprecedented in terms of both its size and its focus on providing habitat for giant kelp. To derive a set of design specifications that should guarantee persistent kelp populations, we addressed issues of what substrates could be used, how large these substrates should be, how high they should be piled, and how they should be distributed. The design study included a review of the historical distribution of kelp on artificial reefs in Southern California, a survey of the natural substrate types that have supported persistent populations, and a comparison of survival on different size classes of rocks. The conclusion is that a low relief reef with a moderate level of sand cover would be the most likely candidate for a successful kelp reef. A 9 ha experimental reef with 56 modules has just been constructed to further define the substrate type and substrate density for the full 61 ha mitigation reef. 2002 International Council for the Exploration of the Sea. Published by Elsevier Science Ltd.