Resistance to temperature stress and Drupella corallivory may promote the dominance of Platygyra acuta in the marginal coral communities in Hong Kong

Abstract

The wide fluctuation in seawater temperature (from 14 °C in winter to 31 °C in summer) has been suggested as one of the factors affecting the diversity of marginal coral communities like those in Hong Kong. We proposed in a previous study that branching corals like Acropora valida were more susceptible to low temperature stress during, and weakened corals became more vulnerable to corallivorous attack by the snails Drupella spp. In the following spring. Acropora spp., however, are not the most common species found in Hong Kong. In the present study, we examined comparable temperature effects, both low and elevated, on Platygyra acuta, one of the most dominant coral species in Hong Kong. Platygyra acuta fragments were exposed to six temperature levels ranging from 14 °C to 32 °C for 7 days before they were exposed to prey-choice experiments with Drupella. Results from these experiments indicated that P. acuta fragments were generally tolerant to temperature changes within the range tested. In contrast to those observed for A. valida, they were not found to be attractive to the subsequent Drupella corallivory. The greater tolerance of P. acuta to both these environmental and biological stresses may have contributed to its dominance in Hong Kong coral communities.

Keywords: Acropora; Coral community structures; Effects-community; Marine ecology; Non-reefal coral community; Predation; Prey-choice experiment; Stress tolerance of corals; Tolerances of massive vs. branching corals.