Interactions among sponges, algae, and coral in Bonaire, Dutch Caribbean: an analysis of sponge and algae prevalence in relation to coral abundance and health

Stressors causing coral reef degradation are making reefs susceptible to domination by other organisms. One documented phase-shift is increased macroalgal cover of deteriorated reefs. Sponges also have the potential to overtake reefs because of their tolerance for rising temperatures and ocean acidification, ability to outcompete corals for space, and tendency to grow on available substrate created by coral mortality. This study aimed to address gaps in the literature on sponge/coral relationships as well as simultaneously study the interactions between coral and both of its potential competitors. Percentage encrusting sponge cover, percentage algae cover, and encrusting sponge density were compared to percentage live, damaged, and dead coral cover to examine the interactions among coral, sponges, and algae. Sponge/coral interactions were also classified to assess sponge aggressiveness. Data was collected at Yellow Submarine dive site using belt transects and photoquadrats. Although no correlations were significant, most comparisons found that sponges and algae decreased with more live coral cover and increased with more dead coral cover. No significant differences among the abundance of sponge/coral interaction types were found on the reef slope, but there were significant differences present on the reef crest. In both locations, most interactions were not aggressive overgrowth interactions. The relationships among sponges, algae, and coral suggest that both sponges and algae tend to grow on substrate made available by coral death. By examining the interactions of both sponges and algae with coral, comparison of these relationships was possible, potentially prompting future work that also assesses multiple ecologically important interactions.

This student research was retrieved from Physis: Journal of Marine Science XIX (Spring 2016)19: 42-51 from CIEE Bonaire.

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