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Discovery of new reef ridge draws attention to these overlooked biodiversity hotspots
View(s):By Tharushi Weerasinghe
New mapping has revealed that the Yakampita and Gingiripita patch reefs, located a few kilometres off the coast of Colombo, are connected by a reef ridge, creating a much larger ecosystem than previously recorded.
An Urban Reef Biodiversity Mapping Project in Colombo, conducted by the Blue Resources Trust and funded by the Lanka Environment Fund, made the discovery while surveying five offshore reefs off Colombo, which the researchers claimed is “the first comprehensive picture of the city’s offshore reef ecosystem.”
“We used a drop camera and an echo sounder for ground truthing and discovered the connection, which meant that the Gingiripita reef system was actually around 130ha, making it much larger than was previously documented,” noted Chanaka Sooriyabandara, Senior Researcher at the Blue Resources Trust.
Pitagala reef
Ecologically, the combined reef exhibits important characteristics, particularly in its northeastern section (Yakampita), which was previously unrepresented in earlier surveys. This section is notably similar to Gingiripita in structure and conditions, and contains areas where hard coral cover exceeds 50%, dominated by extensive stands of small polyp stony corals (Acropora aculeus) and disc corals (Turbinaria mesenterina). Due to this finding, the study team decided to consider both sites as one entity, and subsequently “clumped together” the substrate and fish data from Gingiripita and Yakampita for analysis.
“The size and proximity to the city made the diversity of the species in the reef exciting,” Mr. Sooriyabandara continued. He explained that these offshore reefs play a crucial role in coastal protection, noting their “importance because they act as the first line of defence against tsunamis and storms.” Unlike the more familiar coral reefs in the East or South, these systems are largely flat, with only subtle rises that create what he described as a limited vertical profile. “You have this broad, flat expanse, and then it rises two or three metres before flattening out again,” he said. Though structurally simple, the hard reef surface supports striking coral growth. As he put it, “On that hard surface, there are coral formations that look almost like a field of flowers. It’s beautiful.”
Gingiripita reef system currently has higher coral cover than many of Sri Lanka’s better-known shallow fringing reefs, including those inside Marine Protected Areas (MPAs). As one of the few quantitative assessments of urban reefs in Sri Lanka, the study identifies a clear health gradient: offshore reefs maintain comparatively higher coral cover and community diversity, while nearshore reefs are markedly degraded.
Offshore sites such as Gingiripita and Pitagala (55 ha) recorded higher hard coral cover (23.40% and 20.20%, respectively) and greater species richness, with 77 coral species and 203 fish species documented across all survey locations. The presence and diversity of butterflyfish at Gingiripita also indicate stable reef conditions. Mr. Sooriyabandara noted that these deeper habitats may serve as refugia for corals and reef fish, acting as larval sources as shallow reefs continue to decline due to thermal stress.
By contrast, the nearshore sandstone reef Palagala recorded the lowest hard coral cover (2.3%) and the poorest water quality, driven by land-based pollution, high turbidity and untreated sewage discharge, leading to eutrophic and hypoxic conditions.
Mehak Sangani, Marine Programmes Manager at the Lanka Environment Fund, said the new dataset finally brings long-overdue attention to Colombo’s offshore reefs. “As the first comprehensive study of Colombo’s offshore reefs, this dataset gives these ecosystems a level of visibility they have never had,” she said, adding that it should now “guide management planning and strengthen policy decisions.”
She noted that the findings also challenge long-standing assumptions in Sri Lanka’s conservation sector. “Wilderness has long defined conservation thinking in Sri Lanka, and Colombo’s reefs show that nature persists within human spaces,” Sangani said. She emphasised that conservation frameworks must evolve to protect ecosystems embedded in lived, urban environments—not only those within formally protected areas.
The team was out on the water when their guide Viduranga Cooray, a local fisherman, navigated the boat over the patch that indicated the connection. Mr. Cooray, who has worked in these waters for 12 years, said he relied on his experience: “We fish and dive in these waters regularly, so I was following a gut feeling based on what the team was doing.” He explained that fishermen move across all the reefs, giving them an understanding of reef shapes and shifts that help identify underwater features. Mr. Cooray also noted extensive damage in the arena, as locals recalled the degradation of the reef over time, pointing to the X-Press Pearl disaster, anchor drops and certain fishing practices. “Some of our people still use polawe dela (cast net) with heavy rocks, and that causes a lot of damage,” he said. While dynamite fishing is not common near Colombo because of harbour radar, he added that anchors remain a major threat, and nets often get caught in the shallow reef systems.
Both sandstone and offshore reefs are affected by overfishing, while offshore sites also face anchor damage from increasing commercial ship traffic into Colombo Harbour. These deep-reef systems remain outside existing MPA boundaries and are largely absent from current resource management and development planning.
Prof. Terney Pradeep Kumara, Director General of the Department of Coastal Conservation and Coastal Resource Management, agreed that anchor damage remains a persistent issue in Colombo’s offshore waters. “When an anchor is dropped on a sandy bottom, it will look for something to hook onto, and that usually ends up being a rock or a reef,” he said, adding that reef ridges in the outer harbour area are particularly vulnerable because this is where ships commonly anchor. He noted that the scale and traffic of vessels complicate management, as ships use dynamic stabilisation systems that cause them to shift position, requiring a wide buffer zone while anchored. According to Prof. Kumara, this makes further zoning “not practically possible,” but targeted awareness could help reduce harm. “We can run awareness programmes for ship captains and crew so they can identify reef areas on their maps and radars and avoid them when dropping anchor,” he said.
The report by the BRT notes, however, that coastal development, including port expansion and land reclamation, has taken a heavy toll on Colombo’s nearshore reefs. Yet reef habitats remain largely overlooked in development plans. For instance, the Environmental Impact Assessment for the Colombo Port City (CECB 2015) contains only limited information on the area’s extensive reef systems and biodiversity, suggesting that these ecosystems are not being given sufficient consideration by coastal management authorities.
The study was carried out by a multidisciplinary team led by Nishan Perera, Lead Scientist at Blue Resources Trust, who oversaw project management, field surveys, data analysis, and report preparation. He was supported by researcher Chanaka Sooriyabandara, along with consultant reef ecologist Arjan Rajasuriya, visiting scientist Anjleen Hannak, and volunteers Robin Zeitler and Yannick Martenstyn — all of whom contributed to field data collection and analysis. Volunteer Kavindu Malshan Perera also supported the fieldwork. The team plans on engaging with the Wildlife Conservation Department, as current maritime charts and marine spatial planning documents do not include this data. They aim to map the area and provide detailed ecological information, including species distribution, composition, and overall ecological value, so that government agencies can integrate these findings into future marine spatial planning.
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