Polynesian Corals Say No to Diversity

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When it comes to the symbiotic relationship between reef-building corals and energy-producing algae, “the more the merrier” has been the rule—that is, the more algae types the corals host within their tissues, the heartier the corals, the better they can withstand environmental stress (say from climate change or ocean acidification). Right?

Counterintuitive to the notion that biodiversity is essential for a balanced ecosystem, a University of Hawaii at Manoa study of corals in French Polynesia has revealed just the opposite.

In the field for the National Science Foundation’s Moorea Coral Reef Long-Term Ecological Research, zoologist and UHM PhD candidate Hollie Putnam and team analyzed algae DNA from tissue samples of 34 coral species to determine type and numbers present. While “generalist” corals host multiple algae types that vary among individuals within their species, the team’s findings showed that the stronger, most stress-resistant corals were “specifists”—hosting only one or few algae types.

So are more exclusive corals stronger? Maybe. But which is the indicator species? It’s an even-money bet that the coral specificity is an adaptation to ill-effects of hosting environmentally challenged algae. Stay tuned: part of a $6 million grantfunded by the NSF’s Division of Ocean Sciencesand sponsored by UC Santa Barbara, Putnam and team’s research is set to expand to American Samoa, Hawaii, and Taiwan.