Recoral
Growing corals on offshore wind turbines
With our ReCoral project, we aim to support natural coral growth on the foundations of offshore wind turbines on our Greater Changhua offshore wind farms in Taiwan. If successful, we hope to scale up this coral restoration method to use on other offshore wind farms with similar ecology. ReCoral is a proof-of-concept trial in partnership with the Penghu Fishery Research Center – a research institution specialised in aquaculture and marine biology, under the Taiwan Ministry of Agriculture.
Our non-invasive method involves collecting coral spawn that washes up on the shoreline of the Penghu Islands, cultivating it in the laboratory, transferring viable corals to customised metal frames, and then introducing them to designated locations on turbine foundations, with the intention that they will settle and grow there.
Why could turbine foundations hold a key to coral restoration?
Corals live in symbiosis with an algae called zooxanthellae that relies on sunlight for photosynthesis, meaning they must live near the surface.
But these algae can be badly harmed if the water becomes too warm, too polluted, or too often exposed by extreme low tides, resulting in coral bleaching. As the impacts of climate change accelerate, coral bleaching occurs more and more frequently in the shallow waters where corals live naturally.
On the turbine foundation, by contrast, the corals will have good access to light while being protected from extreme temperatures by the natural circulation of the cooler, deeper water the turbines stand in. Living further out to sea, the corals are also protected from frequent human disturbance.
In practice, there are many challenges to overcome if corals are to make their home on offshore wind turbine foundations. ReCoral is an experiment grounded in laboratory-based trials and meticulous planning. The method needs to be tested and refined, and its impact measured and reported.
Why are we attempting to restore coral ecosystems?
The climate crisis is accelerating global biodiversity loss, threatening the ecosystems that support all life on earth, and nature’s own ability to regulate the climate.
According to the International Union for Conservation of Nature, more than 500 million people around the world depend on coral reefs for food, storm protection, jobs, and recreation.
As a leading renewable energy company, we’ve made the fight against climate change our core business through the deployment of green energy solutions.
But we want these solutions to do more than generate green energy. We’ve set the ambition to achieve a net-positive impact on biodiversity for every new project we commission from 2030 onwards.
A non-invasive, experimental coral restoration method
Our method begins on the shorelines of the Penghu Islands off the west coast of Taiwan. A marine biologist from Penghu Fishery Research Center collects coral spawn that have been released in the annual mass spawning event trigged by a full moon in spring.
Collected coral spawn is then incubated in a flow-through water system in an onshore laboratory. On around day five of incubation, we provide tiles made of brick for coral larvae to seed and grow. The lab has a thermostatic system and artificial lighting to keep the corals alive throughout summer and winter by ensuring the temperature stays close to 23 ˚C.
The lab’s thermostatic system
The corals are then nurtured in the lab for at least six months to ensure they are healthy and strong enough to adapt to the offshore environment.
At the wind turbine foundation, the coral larvae are released into custom-made metal frames that have been attached to the foundation with energise-to-release electromagnets, five metres below the lowest tide level. This location allows the corals to receive adequate light and provides access for deploying the cages and monitoring the corals using remotely operated vehicles.
At the wind turbine foundation, the coral larvae are released into custom-made metal frames that have been attached to the foundation with energise-to-release electromagnets, five metres below the lowest tide level. This location allows the corals to receive adequate light and provides access for deploying the cages and monitoring the corals using remotely operated vehicles.
This is a non-invasive method, meaning we take nothing away from existing coral ecosystems. Instead, we collect some of the billions of egg bundles released during the mass spawning event. There are so many egg bundles that the water’s surface appears pink – but only some of these are fertilised and become larvae.
Under the consent from local government and guidance from the Penghu Fishery Research Center, the eggs we collect are among those that wouldn’t otherwise survive. Collecting them therefore has no impact on the corals that originally released them, nor on the propagation of coral species.
Latest updates from ReCoral
2024
For the next attempt at introducing corals to the offshore wind farm, sample sets will include corals collected and cultured since 2022, 2023, and 2024. This should give scientists a better idea as to the adaptiveness among different age groups to the same location.
We have everything ready to send the corals offshore, but we are dependent on the weather window. The corals should be installed at the turbines sometime between October 2024 and June 2025.
2022
In June 2022, we completed our first seeding trial, using coral spawn collected from the spring mass spawning event, and a mesh cage that we attached to one turbine foundation piece. Early monitoring shows that the corals did not achieve the growth rates we expected.
This first attempt allows us to refine our approach for the next trial. We gathered the following learnings:
- The coral spawning season began later than expected, perhaps as a result of rising water temperatures caused by climate change. This resulted in a very short window of time in which the technical crew could safely introduce the larvae to the mesh cage. In future trials, we will consider the impact of a changing climate on the complete lifecycle of the corals, including coordinating the dates of mass spawning event and the weather window for offshore operations.
- The real-life conditions faced by the corals in the mesh cage were more challenging than those they experienced in the laboratory, with larvae vulnerable to strong currents and competitive species. We will try to recreate these conditions more accurately before transplantation, or delay transplantation until the corals have reached a more resilient stage of their lifecycle.
- The mesh cages proved very difficult to install safely and efficiently at sea. This meant the technical crew was only able to install one out of four mesh cages, dramatically reducing the sample size for the experiment. We have therefore since redesigned the mesh cages to make installation easier, as well as improving the environment they provide for coral growth at different stages of maturity. We will now use metal frames instead, and will use a remotely operated vehicle to install them.
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The potential long-term benefits of ReCoral
Ultimately, we hope to refine a method that can be deployed at a much greater scale than the trial at Greater Changhua offshore wind farms. If we are successful, this coral restoration method could be applied to the foundations of offshore wind turbines in any tropical waters around the world, boosting ocean biodiversity.
Turbine-born larvae as a lifeline for natural reefs
Corals growing on offshore wind turbine foundations would also release their own spawn, which could be carried by ocean currents to settle naturally elsewhere. This could boost genetic connectivity across oceans and support the restoration of existing coral reefs.
Larvae generated at offshore wind farm sites could also be captured, then transported to and released at naturally occurring reef locations.
In either case, restoring naturally occurring reefs would, in turn, support healthy stocks of fish and other reef species.
In the latest coral reef restoration guide released by the United Nations Environment Programme, the release of larvae is considered as ‘potentially one of the most scalable methods for coral reef restoration’.
Sharing findings with the coral conservation community
We will share what we find with the broader coral conservation community and with other wind farm developers. Halting and reversing biodiversity loss must be a collaborative effort so whether or not our pilot succeeds, we hope our findings will be useful for future endeavours in coral restoration.