ESR 22:183-189 (2013)  -  DOI: https://doi.org/10.3354/esr00544

ABSTRACT: Since the 2006 listing of the staghorn coral Acropora cervicornis as threatened under the US Endangered Species Act, interest has increased in its culture for laboratory studies, restoration and ex situ conservation efforts. A pervasive problem in coral culture is substrate overgrowth by algae and other spatial competitors. We conducted a laboratory study to examine the utility of introducing herbivores, juvenile variegated sea urchins Lytechinus variegatus, to tanks containing small (<1 cm²) A. cervicornis ramets. Growth of coral ramets on ceramic tile substrates was monitored in recirculating seawater tanks over 210 d and measured in terms of area change under 3 treatment conditions: (1) presence of laboratory-reared, juvenile, variegated sea urchins; (2) weekly scraping of algal turfs from the tile substrate by means of a razor blade; and (3) absence of both urchins and manual turf removal (i.e. control). Over the course of the study, coral area decreased in the control treatment, but increased in the scraped and urchin-containing treatments. All 3 treatments differed significantly from one another, with the highest growth rate (3.1 mm² d^-1) associated with the manual removal of algal competitors, followed by the urchin (1.9 mm² d^-1) and control treatments (-0.8 mm² d^-1). Given the relative ease of L. variegatus culture, the incorporation of variegated sea urchins in the coral ramet production process appears to provide at least a partial substitute for manual algal removal. Although coral growth in the presence of urchins was slower than with manual removal, human labor costs associated with the latter may out-weigh any production rate improvements in large-scale operations.

KEY WORDS: Sea urchin · Coral production · Lytechinus · Algae control