Unlocking Resilience Drivers to Inform Pacific Coral Reef Management Active

Coral reefs are threatened by climate change because warming ocean temperatures are causing corals to bleach (i.e. lose the algae that provides them with the majority of their energy) which can lead to coral starvation and death. Local environmental conditions can contribute to either the resilience or susceptibility of corals to the global stress of climate change. One such factor is the local nutrient input from terrestrial sources. Corals near remote islands with abundant seabird populations have been found to have increased growth rates and are more resilient to bleaching events than corals near islands without seabirds. Seabirds supply the reef with ample nutrients via their guano (seabird excreted waste) and this natural nutrient source has been found to be beneficial to corals. In contrast, corals near populated islands have high levels of human-induced nutrients entering the coastal environment via wastewater. This source of nutrients has been found to be detrimental to corals, causing decreased growth rates, coral disease, and lower tolerance to stress, such as coral bleaching.



The objective of this project is to investigate corals' response to natural vs human-induced nutrient sources and to test if the benefits of guano to corals can be simulated in areas without large seabird colonies. An experiment will be conducted at the Hawai'i Institute of Marine Biology by placing coral fragments in seawater enriched with either seabird guano, wastewater effluent, or a fish solution. The fish solution will be tested to determine if the beneficial properties of guano to coral can be replicated and will be created by rendering fish waste from local commercial fisheries into a solution with similar properties to guano. Corals will be run through a simulated bleaching event and coral condition and resilience will be measured to compare how each nutrient treatment affects the corals’ ability to tolerate increased water temperatures.



This project addresses knowledge gaps that could increase reef resilience by exploring management actions that support coral reefs’ persistence through global climate change. Results from this project will provide information on how guano is influencing reef resilience on remote island atolls compared to how human-induced nutrient pollution is impacting reefs near populated islands. Additionally, the results will investigate the differences in natural vs. artificial nutrient enrichment to coral reefs and the possibility of repurposing fish waste with this novel resilience strategy.