Gombessa Expeditions - Tubbataha Reefs Deep Dive
The Tubbataha Reefs Natural Park, located in the heart of the Philippines, is one of the world’s most iconic and well preserved marine protected areas in Asia. Established as a no take zone and recognized as a UNESCO World Heritage Site since 1988, it’s home to vibrant coral reefs, rare marine species, and crystal-clear waters that attract divers and scientists from all over the world.
For over 25 years, park rangers and scientists have monitored multiples ecosystems and species within the park, including coral reefs by conducting transects at depths of -5 and -10 meters, within the photic zone (with abundant light supply). Below this zone lies the mesophotic zone, between -60 to -150m. However, due to the remoteness of the area and the technicity of diving at such depths, diving is not allowed below -40m within the park for regular divers.
As a result, a large part of Tubbataha ecosystem’s remains unexplored and unknown. This Gombessa Expedition aims to venture into these rarely glimpsed depths to achieve three primary goals.
Expedition Goals
SCIENCE - Characterize and inventory Tubbataha's mesophotic ecosystems, providing essential data for park management. Test a new, innovative and patented tool for rapid data collection: STEED.
IMAGE - Illustrate these hidden habitats through underwater photography and a short documentary film, in order to share the richness and importance of the mesophotic zone in this region. Unearth and capture portraits of rare or never-before-photographed species.
ADVENTURE - Carry out the first deep diving campaign in Tubbataha. Demonstrate the feasibility of surveying along a vertical gradient of ecosystems between -120 meters and -10 meters in a single, carefully planned dive, using STEED methodology. The challenge of studying deep ecosystems in detail, even though these depths preclude long observation times.
Outcomes
13 deep dives in 13 days on site, for a total of 208 hours of immersion for the 4 divers. The Gombessa team studied 30 underwater sites from -127 meters to -9 meters depth, collecting data on fish species, gorgonians, mobile invertebrates and benthic organisms.
They discovered that Tubbataha's deep reefs comprise eight different habitats, distributed along a specific depth gradient. These habitats range from the well-known reef ridge, around -10 meters depth, where sunlight is abundant and coral colonies thrive, to the deep slopes, at over 120 meters, where light is very low and sponges and encrusting organisms dominate.
Some key discoveries
A central mesophotic zone between -60 and -90m, home to a great diversity and abundance of fish and invertebrates. This habitat is built up by large gorgonians, which structure the habitats and communities. It is home to a different community of fish species to that in the shallow zone around -10m.
108 species of fish were observed, including 10 species never observed in Tubbataha before. But also, 11 species of cowries and 17 genus of gorgonians.
The team found rare and beautiful fish species, such as the Colin’s angelfish and bellus angelfish, which live specifically at certain depths and had never before been recorded in Tubbataha.
The team also observed a remarkable abundance of numerous species of gorgonians and sponges, all very large (over 2 m high). These slow-growing organisms are necessarily old and indicate a stable, undisturbed environment.
The team observed the impact of a past mortality event on gorgonian colonies. At two sites, between -10m and -40m, 100% of colonies showed signs of necrosis, likely caused by a cold-water upwelling, and were already colonized by the parasitic anemone Nemanthus annamensi.
Combining drone images and in-situ observations, the reef’s crest revealed cracks and significant irregularities, suggesting that sections of the reef may have broken off and settled at greater depths due to gravitational forces. In addition, while exploring the relief and topography of the mesophotic zone, the team observed coastal notches indentations on wall and deep reefs indicating sea level variability since the Last Glacial Maximum.
Exploring the unseen depths
These deeper, hard-to-reach reefs deserve special attention, as they harbor a great diversity and abundance of life essential to the health of the entire reef system. This expedition was the first of its kind in Tubbataha, combining rigorous scientific protocol, deep diving and outreach work. The STEED methodology significantly improves the ability to collect data on deep ecosystems where working time is limited, by offering the possibility of collecting data on 4 biotic communities at 4 depths (120, 80, 40, 10 m) in a single dive. This opens the way to a better understanding and knowledge of mesophotic ecosystems. The data collected by the Gombessa Expeditions team will help scientists and park managers to better protect these key habitats.
Complementing the scientific advances, the photos and videos will help raise public awareness of a part of the ocean that most people never get to see, but on which we all depend.
The Team
Laurent Ballesta photographer deep diver & biologist.
Florian Holon, PhD in Marine ecology & deep diver.
Thomas Pavy, Engineer in Marine Ecology & deep diver.
Yanick Gentil, Professional diver & underwater cameraman.