Submerged beneath the shallow waters of the Bazaruto Archipelago off Mozambique, drowned forests dating back thousands of years have been transformed into vibrant peat reefs. Documented by researchers from the Bazaruto Center for Scientific Studies, these rare marine habitats harbor rich biodiversity comparable to nearby coral reefs.
Off the coast of Mozambique in the Western Indian Ocean, marine researchers have uncovered an unexpected ecological phenomenon. Ancient coastal landscapes that once flourished above water are now submerged beneath the sea as firm peat platforms, serving as thriving underwater sanctuaries where marine life can take hold.
Radiocarbon Dating Reveals Forests That Grew Up to 5,000 Years Ago
The origins of these submerged formations stretch back thousands of years. Radiocarbon (14C) dating shows that the underlying peat deposits formed between approximately 300 and 5,000 years ago. Chemical analysis confirms that the material originated primarily from coastal land plants and trees, preserving the chemical signature of a long-vanished terrestrial world.
As sea levels rose over the millennia, ocean waters flooded coastal swamps and forests. Subsequent wave action stripped away the overlying sand and sediment, exposing solid peat platforms on the seabed. Because the surrounding coastline features very little natural hard seabed and consists mostly of shifting sand, these exposed layers provide a rare, stable substrate.
Bazaruto Center for Scientific Studies Documents Surprising Fish Diversity Without Coral
A research team led by Mario Lebrato from the Bazaruto Center for Scientific Studies (BCSS) Ocean Observatory—founded in 2017, working alongside collaborators from universities in the United Kingdom, the United States, and Canada—surveyed three of these peat reefs alongside a nearby true coral reef. The observatory has generated more than 22 million measurements across over 30 chemical, environmental, and biodiversity variables spanning an approximately 6,850 square kilometer monitoring area across six interconnected ecosystems and 14 long-term monitoring stations. Despite holding zero living coral, the peat formations support a complex ecosystem where seagrasses and seaweeds grow directly on the dark substrate.
Crevices and ledges across the platforms offer critical shelter for spiny lobsters, oysters, barnacles, and juvenile fish. Surveys recorded 26 to 36 small fish species on each peat reef—a diversity mix comparable to neighboring coral formations—including young snappers and grunts that use the area as a protective nursery.
Mario Lebrato, lead author and co-founder of the BCSS Ocean Observatory, said, What was once a forest floor is now a nursery for reef fish,
adding that the team was surprised by how much life these ancient peat deposits support, and how many species move between them and the coral reefs nearby.
He noted that this coastline has very little natural hard seabed, mostly shifting sand. When rising seas expose these old peat layers, they create rare, solid habitat where marine life can settle, hide and feed.
He further stated that the ability to demonstrate the vitality of these habitats as a result of our continuous observation excites me for the prospect of implementing conservation policy that protects similar regions around the world.
Larger marine animals, including sharks, rays, and turtles, frequent both the peat and coral reefs. Herbivorous megafauna such as green turtles and dugongs also graze on associated seagrass patches.
Harsh Daily Conditions Test the Resilience of Shallow Peat Platforms
Life on the submerged forest floors is demanding. Sitting just 2 to 4 meters (about 7 to 13 feet) deep, the platforms are regularly exposed by tides and experience intense sunlight. Water temperatures can swing by four degrees in a day, recording values between 24.5 and 28.6 degrees Celsius (76.1 and 83.5 degrees Fahrenheit) within a single day. In addition to thermal swings, storms and cyclones routinely batter the formations, burying, uncovering, or fracturing them, with many structures ultimately vanishing due to erosion and moving sand.
Unresolved Carbon Questions and Conservation Implications for Tropical Coastlines
Beyond biodiversity, the discovery opens a major scientific inquiry regarding regional carbon storage. Chemical analysis indicates that some peat samples contain up to 40 percent organic carbon by dry weight. While terrestrial peat swamps hold 1,000 to 2,000 metric tons of carbon per hectare (2.5 acres) below ground, scientists emphasize that the present-day role of these submerged reefs in carbon cycling remains unmeasured and unresolved.
Researchers note that answering these questions requires dedicated measurements of peat thickness, density, carbon stocks, burial or erosion rates, and greenhouse gas fluxes. Establishing whether these formations qualify as “blue carbon” habitats could shape future coastal management strategies.
The findings suggest that similar undiscovered peat reefs may lie unrecognized across Southeast Asia, the Caribbean, and West Africa. As coral reefs face escalating pressures from environmental change, these overlooked habitats could provide vital backup refuges for marine species, prompting calls for their inclusion in coastal maps and conservation policies.