Key Findings – Moorea Coral Reef LTER

Credit: MCR LTER

Researchers at MCR LTER have been at the forefront of evaluating how OA will affect the structure and function of future reefs. The ecosystem engineers that structure coral reefs – stony corals and calcified algae – are uniquely threatened by low seawater pH. Using time series data to determine experimental conditions, researchers have tested for coral susceptibility to low seawater pH, the dependence of these responses on space, time, and functionality scales, and the implications for future coral reefs.

Credit: MCR LTER

The diverse coral community on Moorea’s outer reefs has repeatedly shown a remarkable ability to recover rapidly following massive disturbances. In the last decade, a predator outbreak and cyclone devastated coral across the seascape, yet recovery was more rapid than has been observed anywhere in the world. Moorea Coral Reef LTER researchers have gained critical insights into the processes, connectivities, and feedbacks governing coral reef resilience. This has provided the basis for general management strategies to help restore and strengthen coral reef community resilience.

Credit: MCR LTER

Reefs worldwide have abruptly and increasingly shifted from coral to seaweed dominated communities. Experiments at MCR LTER revealed that a large disturbance can cause a coral reef to flip to seaweeds indefinitely. Experiments and models showed that multiple stable states (e.g. corals or seaweeds) can continue to thrive under the same levels of herbivory. They also discovered that the seaweed state is stabilized by the development of structural and chemical defenses that reduce the palatability of mature (but not juvenile) algae.

Credit: Russell Schmitt

The powerhouse mutualism between the coral animal and its symbiotic dinoflagellate algae is the backbone of coral reef ecosystems. Moorea Coral Reef LTER research has produced counter-intuitive results, specifically that flexibility with respect to symbionts does not automatically make corals resilient – a finding that has had profound implications for understanding the susceptibility of coral colonies to stress. Similarly, MCR LTER researchers have shown that major feedbacks involving other microbes affect coral health, particularly bacteria key to the dynamic nutrient cycling on reefs.