The role of mesoscale-driven connectivity patterns in coral recovery around Moorea and Tahiti, French Polynesia

Coral reefs are declining due to anthropogenic warming. Nonetheless, some have recovered quickly from repeated bleaching events. Coral recovery depends on adaptation capabilities, fishing pressure, overall number of stressors, reef conditions before the event, and degree of connectivity. Coral reefs that are connected to many others can receive viable larvae and regain coverage faster. Around Moorea and Tahiti, within the Society Islands of French Polynesia, coral cover has regained its previous levels rapidly, despite several mass bleaching events over the past three decades. Here it is explored whether the connectivity with distant reefs may support such recovery by modeling the transport of coral larvae around the islands over 28 years. Ocean currents enable connectivity with the Tuamotu Islands, ~ 250 km to the northeast, that act as sources to Moorea and Tahiti for pelagic larval durations of three weeks or longer. The circulation around Moorea and Tahiti is very dynamic; mesoscale eddies can also halt the connectivity with the Tuamotu Islands and sporadically transport larvae from reefs to the west and southeast instead. With many undisturbed coral reefs within a 300 km radius and strong mesoscale variability, a dynamic, long-range connectivity may explain the recovery of reefs around Moorea and Tahiti.