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

Abstract

Growth rates of 7 species of Caulerpa were measured in sifu at depths of 20 m in Salt River canyon, St. Croix, US Virgin Islands. Mean stolon elongation rate for all species of Caulerpa studied was approximately 1 cm d-l. Dry biomass accumulated in this new growth was less than 10 mg d-', and specific growth rates were less than 10 % d-'; 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 burled to simulate effects of animal activities had significantly lower stolon elongation, biomass accumulation, and specific growth rates than control plants. We hypothesize that the productivity of these algae is limited in part by animal-mediated sediment disturbances.