A new scientific study by PICRC identifies key drivers in coral reef recovery

Across the world, coral reefs are declining as a direct result of human interference. As the global climate continues to shift, these fragile, underwater habitats bear mass disturbances such as increased storms, mass bleaching events, and crown of thorn outbreaks. Unlike many reefs worldwide, coral reefs in Palau have been fortunate not to face any mass-disturbances from 1998 to 2012.

In a study published in the scientific journal, Proceedings of the Royal Society Biological Sciences, PICRC researcher Marine Gouezo and her colleagues from Palau International Coral Reef Center (PICRC), Southern Cross University, Australian Institute of Marine Science, James Cook University, and CSIRO Oceans and Atmosphere, were able to determine that it takes around 9 to 12 years for coral reefs to completely recover in the absence of large-scale disturbances.

Understanding coral recovery has been a challenge due to insufficient long-term data and the frequency of disturbances. This study is one of few that have been able to track complete coral recovery expanding over 14 years free from any mass disturbance.

In 2001, PICRC began long term monitoring to track coral reef recovery following the 1998 mass bleaching event. Through these monitoring efforts and analyses, researchers identified three key drivers of coral reef recovery: larval connectivity, a high density of juvenile corals, and a high abundance of parrotfish.

Larval connectivity refers to the amount of coral larvae an area receives following a disturbance. In this study, coral reefs that received more coral larvae from nearby reefs recovered faster. A high density of juvenile corals was another strong indicator that the reef was on its way to recovery. Additionally, parrotfish positively affected juvenile corals found in a given area. Algae and corals compete for space. By eating algae, parrotfish provide ample space for corals to grow and thrive.

While the entire stretch of the eastern reefs was decimated by two super typhoons in 2012 and 2013, reefs on the west have not suffered from any major disturbances since 1998. These reefs are believed to have reached their coral dominant state or ‘climax’ state.According to PICRC Researcher, Marine Gouezo, lead author of study, “Understanding this process of recovery will allow for the better management of our coral reefs as pressures from climate change escalate. This study demonstrates the large role herbivorous fish play in reef recovery. It also emphasizes the possibility of managing reefs depending on their level of connectivity as well as the possibility of implementing coral restoration projects to boost recovery and the overall resilience of coral reefs.”