CCMI sees outstanding success in coral restoration methodology

December 6, 2020

Coral reefs are biologically diverse and require a range of species to maintain a critical balance needed for a ‘healthy coral reef ecosystem.’ As ocean temperatures continue to rise, there are calls to tackle the issue of declining coral reefs more directly, as local protection measures struggle to mitigate global impacts. Coral restoration has been an emerging yet still embryonic technique that provides hope for coral conservation, and it is used to maintain (or regain) coral reef biomass. Coral nurseries have yielded great success around the globe, as fragments are grown in ideal conditions, free from predation and disease. However, the core goal for restoration methodology is to re-wild the natural reef by outplanting nursery fragments to the substrate, replacing corals that have been lost through mass disease and bleaching events, which can devastate the reef ecosystem. Yet whilst nurseries have flourished, re-wilding techniques have been met with mixed success rates and often, high mortality of outplanted corals (circa 80% mortality).

CCMI initiated a coral restoration program eight years ago, supported by Dart Cayman Islands, the AALL Trust, Stuarts Walker Hersant Humphries, Cayman Water Company and the Ernest Kleinwort Charitable Trust, to help preserve the genetic diversity of the endangered coral species, Acropora cervicornis, or staghorn coral. Through various experiments with different restoration techniques, the team is learning best practice and improving their success. Experiental efforts include genetic testing and understanding resilience to disease as well as establishing best practices for growing more robust corals in the nurseries that can withstand storm and surge impact. Through meticulous science-based investigation, the team at CCMI now knows the best ways to select and orient corals in their nursery, and they are also discovering the best techniques for outplanting to promote growth and survival. CCMI’s recent dome outplanting project showed 89% survival rates out of more than 120 coral restored onto the reef. This gives hope for the potential to outplant large areas of the reef, increasing reef complexity and promoting biodiversity. Scaling up the restoration project, with potential for all three Cayman Islands, is a long-term goal for the project.

Dr Gretchen Goodbody-Gringley, CCMI’s Director of Research indicates that the project creates great hope for restoration: “We executed a large restoration project comparing the success of outplanting at different sites and depths, which is showing huge success with 89% survival rates for corals outplanted onto the reefs. We actually had nearly 100% success on several of the test sites, but one site was impacted by disease, a very real and prominent threat to coral reefs. These types of studies are pivotal to our success in restoring the reefs and ensuring that every coral we raise in our nursery and plant out onto the reef has the highest chance of survival.”

The CCMI team has learned that site selection for outplanting is critical to restoration success, and next steps will aim to determine what environmental features may be driving the differences in success. Frustratingly, it is not a case of just put the corals out via the new domes and see how they go; further understanding as to which corals can be resilient to disease and temperature is critical to the restoration process. Moving forward, the CCMI team will test temperature tolerances and how differences in physiology among individual colonies may impact survival.

The reefs in the Cayman Islands, Little Cayman in particular, are ‘relatively healthy’ according to CCMI’s 21 years of data collection, using AGGRA protocols and the Healthy Reef Initiative to measure and gauge reef health. Reef decline is prevalent in the Caribbean and around the globe, and we know there is a limited window of time to protect coral reefs for the future. CCMI’s research mission is to promote the resilience of coral reef ecosystems and this project has very scalable conservation outcomes that could make a significant different to reef health in the future.