An NCCOS-funded study used modeling to demonstrate that the quick recovery of bleached corals in the past five mass bleaching events in Moorea and Tahiti (within the Society Islands of French Polynesia) may be the result of long-distance connectivity with the Tuamotu Islands and undisturbed coral reefs within a 300 km radius.
Coral reefs are declining worldwide due to a myriad of stressors, including increasing ocean temperatures. When temperatures increase, many corals respond by bleaching. Bleaching occurs when the algae living with the coral polyps are released and the coral takes on a pale, or “bleached,” appearance. The coral’s recovery depends on adaptation capabilities, fishing pressure, overall number of stressors, reef conditions before the event, and degree of “connectivity” to other reef systems.
In Moorea and Tahiti, there were five mass bleaching events in 1994, 2002, 2007, 2016, and 2019. Researchers used models to show that during these years for corals with a three-week pelagic duration (i.e., the amount of time they spend in the water column before they settle) could have traveled up to 250 km to reach Moorea and Tahiti from the Tuamotu Islands to the northeast, replenishing the damaged areas with healthy larvae. With many stressors and bleaching occurring more frequently though, this may still result in a loss of biodiversity as corals with a shorter pelagic duration time would not be able to be replenished from afar.
The study received part of its funding from an NCCOS project investigating coral ecosystem connectivity in the Northwestern Gulf of Mexico.