Underwater gardeners are growing resilient coral reefs in Kenya. It’s not altogether different from terrestrial gardening: in an underwater nursery, divers cultivate coral fragments on plugs, allowing them to grow large enough for ‘planting’. Rather than using fertilizer or soil, they mash together an epoxy glue that holds underwater and transplant the coral plugs to degraded reefs with nails and screws.
The gardeners return frequently to track the coral’s survival, growth and health, tending to them with care. While weeding out excess algae, fish swarm around, enjoying a feast of invertebrates dusted up by the gardening activities. Much like their efforts to reforest degraded woodlands, A Rocha Kenya is restoring a vibrant reef ecosystem in Watamu Marine National Park.
Watamu is one of the world’s oldest marine parks, established in 1968. Since then, this 10 km² area has been protected by the Kenya Wildlife Service against human threats like fishing and unsustainable coastal development. However, the park’s coral reefs still face the threat of increasing thermal stress and coral bleaching.
A vital reef turned skeletal
Historically, Watamu’s coral reef was magnificent with diverse corals of vibrant colours that housed a myriad of fish and other marine life. Research on these corals has been ongoing for over 40 years, so we have a strong understanding of how they have degraded over time. The reef was once considered healthy, boasting 40-50% coral cover. However, a devastating global bleaching event in 1997-1998 drastically changed the landscape. The reef turned completely white, and coral cover dropped to a mere 10% between 1998 and 1999.
Corals are not inert, colourful rocks: they are animals, closely related to jellyfish and anemones. Corals have a symbiotic relationship with the tiny microalgae that live inside their clear tissue and give the corals their stunning colours. Coral protects and gives essential nutrients to the microalgae. In return, the algae produce sugars through photosynthesis that feed the coral.
Rising sea temperatures have caused this vital relationship to break down. When waters warm to a stressful temperature, algae becomes toxic to the coral animal, and the coral expels it to survive the heatwave. This leaves the coral bleached and vulnerable, its white skeleton showing through the transparent tissue. Eventually, the corals may die, and the hundreds of thousands of marine animals they support will suffer, as well.
Watamu’s coral reef has never been the same since the bleaching event in the ‘90s. Corals have recovered somewhat, but continued and more frequent bleaching events have ravaged corals in Watamu and around the world. A devastating bleaching event in 2024 may have had an even worse impact on the reef. Before the 1990s, bleaching was a small, localized occurrence in response to ocean pollution after a storm. Mass bleaching events are becoming a regular occurrence, but they are a modern phenomenon.
Learning from corals’ resilience
Every six months since a bleaching event in 2020, A Rocha Kenya revisits over 600 tagged corals in 70 permanent plots in the marine park to see how the corals are growing. They also assess if there are bleaching-resistant colonies and if baby corals (recruits) have settled in the plots. Repeated bleaching has caused the coral cover to decline from 35% in 2020 to 11% by April 2025. Nevertheless, A Rocha observed many corals that survived, pointing to signs that some corals may be developing increased thermal tolerance.
While corals can recover from bleaching, this depends on the thermal adaptation and regrowth of corals outpacing the rate of rising sea temperatures. Reef recovery is further constrained by low coral recruitment and the overgrowth of dense macroalgae, which outcompete coral for space and light. Thankfully, corals that survive bleaching often exhibit increased thermal resistance, making them more likely to survive future events.
This sign of hope catalyzed A Rocha Kenya to implement the first Kenyan coral gardening project in a protected area. After years of observing and documenting the reef, A Rocha began a restoration pilot in Watamu in April 2024, in partnership with Coral Reef Care and the Kenya Wildlife Service. Propagating and planting these thermally resistant colonies back onto the reef could help overcome the issue of low recruitment and speed up the recovery of Watamu’s reefs.
The coral gardening process takes place in three stages:
- Collecting coral fragments. The collected fragments are either Corals of Opportunity, (COOs) – naturally broken fragments found in the ocean from various coral types – or fragments from Thermal Resistant Colonies (TRCs), colonies that have naturally adapted to withstand higher temperatures without bleaching or suffering mortality.
- Coral ‘gardening’ and transplantation to the reef. Collected fragments are taken to underwater nurseries. COOs are glued onto plugs or zip-tied to nursery tables for stabilization while TRCs from outside the park are placed in nurseries to monitor growth before transplantation. Local TRCs are directly transplanted to reefs after collection. Once the corals in the nurseries have grown to a suitable size, they are carefully transplanted back onto degraded reef areas.
- Monitoring and maintenance. TRCs are often prioritized for planting in areas most affected by bleaching. The transplanted corals are regularly monitored to track their survival, growth and health. This includes checking for signs of disease, predation or bleaching. The team also weeds the substrate and the nurseries regularly to ensure the baby corals have the space and light they require to thrive.
Nurturing an adaptive coral garden
In 2025, A Rocha Kenya and their partners planted 1,565 corals within Watamu Marine National Park as part of the ongoing coral restoration efforts. Additionally, the marine team is introducing heat resistant corals from outside Watamu to increase genetic diversity and restore some of the species that have disappeared from the park. Following El Niño-related stress, resilient coral species (including Stylophora subseriata and Porites cylindrica) sourced from Kuruwitu were introduced and are currently under close monitoring to assess their adaptation and growth. An additional 116 broken coral fragments were collected from nearby Uyombo.
Monitoring remains continuous and adaptive. Survival rates, bleaching responses and growth patterns guide restoration decisions, with interventions designed as structured experiments to identify coral species and genotypes capable of withstanding increasing thermal stress and changing ocean conditions.
The coral garden is a community effort, engaging tourists, volunteers and local boat operators in hands-on marine conservation of a beloved ecosystem. In 2025, A Rocha Kenya organized 58 boat trips, totaling over 470 diver-hours. Collaboration with key partners – including Kenya Wildlife Service, Bahari Hai Conservation, Turtle Bay Dive Centre, and Coral Reef Care – is central to the project’s success.
Since March 2026, Kenya Wildlife Service has expanded the restoration initiative by bringing in additional partners, including IUCN Kenya, Kenya Marine and Fisheries Research Institute and others. This collaboration aims to scale up reef restoration using a range of techniques, such as underwater sculptures, reef stars and artificial reef blocks. These efforts are also intended to create an alternative tourism site, helping to reduce visitor pressure on the natural coral reefs.
Why work so hard to protect these corals? Coral reefs are some of the most diverse and valuable ecosystems on Earth. They support more species per unit area than any other marine environment, including about 4,000 species of fish, 800 species of hard corals and thousands of other species. Scientists estimate there may be millions of undiscovered species of organisms living in and around reefs. This biodiversity is considered key to finding new medicines for the 21st century. A Rocha also believes that coral reefs have value independent of any use to humans and should be protected regardless, as creatures loved by God.
The future of our coral reefs depends on their ability to regrow faster than the heat rises. In a time of compounding crises from climate change to biodiversity loss, we are embracing creative solutions to protect life on Earth.
