Growth and sediment disturbances of Caulerpa spp. (Chlorophyta) in a submarine canyon

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Abstract
Growth rates of 7 spp. of Caulerpa [C. sertulariodes, C. sertulariodes var. lycopodium f. elegans, C. mexicana, C. cupressoides, C. cupressoides var. flabellata, C. prolifera, C. taxifolia] were measured in situ at depths of 20 m in Salt River canyon, St. Croix, USA Virgin Islands. Mean stolon elongation rate for all species of Caulerpa studied was .apprx. 1 cm d[day]-1. Dry biomass accumulated in this new growth was < 10 mg d-1, and specific growth rates were < 10% d-1; these values are low compared to rates of many benthic macroalgae. Macrofauna (conchs, ghost shrimp, hermit crabs, urchins, rays) were observed disturbing sediment. Plants were uprooted or buried by animals that foraged, burrowed and made excavations or sediment mounds. Plants experimentally uprooted or buried to simulate effects of animal activities had significantly lower stolon elongation, biomass accumulation and specific growth rates than control plants. The productivity of these algae is apparently limited in part by animal-mediated sediment disturbances.