In November 2021, we launched our pilot nursery at “La Calera,” a now exticnt historic reef at the western end of Puerto Villamil bay. Our mission was to determine the feasibility of coral rearing in this unique environment and understand how seasonal ocean changes affect coral survival, health, and growth in the Galapagos archipealgo. For this purpose our team constructed a pilot nursery to test for different rearing methods.
Methods
We tested various techniques and methodologies for the cultivation, allowing for identification of rope nurseries as the most cost-effective (<$60) and straightforward method, making it perfect for rapidly rearing coral fragments. This system, which involves ropes suspended over a metal structure, was ideal for reproducing the most abundant varieties of Pocillopora in the area.
Using our comprehensive baseline from Puerto Villamil, our team carefully selected and revisited 12 different coral donors. We collected coral fragments and meticulously labeled and photographed each one of them before placing them in our nursery by early January 2022. We cultivated a total of 240 corals which we monitored for an entire year, studying the effects of the warm and cold seasons, and providing us with valuable insights into their survival, health status, and growth.
Our dedicated team maintained the nurseries with weekly cleanings and monthly monitoring. We developed a detailed monitoring protocol with a scoring system based on a 0-5 scale to study live tissue cover, algal competition, and bleaching, ensuring precise and accurate data collection.
In order to measure coral growth and development and its relationship with Galapagos seasonal water temperature differences, the project undertook detailed coral measures at the end of every season. Using photographs and digital image processing softwares, we were able to identify the fastest-growing candidates for maintaining the nursery, and study the relationship between coral development and water temperature more closely. The project has thus created the first coral growth database in the Galapagos, which has revealed interesting trends and growth cycles with respect to seasonality and coral varieties. Information which will allow our team to calculate the current and forecasted impact of coral restoration, its complexity and potential for habitat creation, reef accretion and carbon sequestration.
During the coral rearing period, the seasonal water temperature fluctuations of the Galapagos played a pivotal role. During the warm season (January-June) corals grew healthy and with minimal mortality, nevertheless, during the colder months of the year (September-November), cold-water bleaching stress was observed in several coral varieties, potentially affected by the cold-water conditions intensified by “La Nina”. During this season, cold-water bleaching became the main driver of mortality, bleaching and tissue loss, lowering survival rates down to 85.8%. Nevertheless, it allowed the team to identify the most resistant coral colonies and the lower thermal threshold of 19C for coral survival in the Galapagos.
Results
- The Galapagos warm season (January – June 2022) proved to be the most favorable time for healthy coral growth and development.
– Out of 240 corals, only 9 died, resulting in an impressive 96.25% survival rate.
– Average live tissue cover corresponds to 89.4%.
– Warm season yielded significantly higher growth rate of 85.6% per 100 days.
- The Galapagos cold season (June – December 2022) brought colder than usual waters to the islands, product of the severe 2022 La Niña, decreasing overall survivorship and health.
– Despite the severely low water temperatures, the pilot nursery maintained a high survival rate of 85.84%, with only 33 corals being lost.
– The average live tissue cover decreased to 75.28%, product of cold-water bleaching and stress.
– Cold season yielded a significantly lower growth rate of 47.6% per 100 days.
- Overall growth in our coral nursery exceeded 32 cm²/year, and over 4 cm linear growth.
- Each coral variety had significantly different survivorship and growth rates, providing the insight necessary to select the most resilient varieties.
- Identification of rope nurseries as the most cost-effective (<$60) and straightforward method, making it perfect for rapidly increasing nursery capacity.
- Outplanting techniques with cement mix were utilized and perfected to succesfully transplant 207 mature coral colonies.
- Coral transplants proved to be highly successful, with near 100% survivorship.
Conclusions
These results highlight the Galapagos as a promising location for coral gardening and restoration practices. Despite the less than favorable conditions product of 2022-2023 La Niña conditions, the coral gardening method in the Galapagos has demonstrated higher survival rates than any other regional trial, surpassing world survivial averages by more than 20% and sustaining significant growth and coral health.