Off the coast of Mozambique, remnants of ancient forests lie beneath the sea, having grown along the Indian Ocean coast thousands of years ago. Today, these submerged remains serve as a refuge for fish, lobsters, and other marine life.
Researchers studying the Bazaruto archipelago discovered that ancient peat deposits, formed from decaying plant material, have turned into underwater reefs. Although they may not resemble traditional coral reefs, they support many of the same fish species.
These findings demonstrate an unexpected aspect of marine life in the region and highlight how much more scientists have yet to learn about underwater habitats. Approximately 5,000 years ago, rising sea levels flooded coastal forests and wetlands. Over time, layers of plant material compressed into peat, preserving the landscape.
As sand shifted and waves eroded the seabed, parts of this ancient peat became exposed. Their rough surfaces and crevices provided shelter for marine creatures. Researchers dated samples of these reefs to approximately 300–5,000 years ago, confirming that the formations originated from terrestrial vegetation rather than marine plants.
During surveys in 2023, divers recorded the presence of fish, sharks, rays, and turtles around the peat reefs. Young snappers and grunt fish found shelter among these formations, while spiny lobsters occupied their cracks and protrusions.
On each of the three surveyed sites, the reefs supported 26 to 36 species of small fish. A nearby coral reef supported 54 species, but researchers noted that different habitats attract different marine communities.
The data suggests that these ancient forest remnants provide an important refuge and potential nursery grounds, especially in areas where natural hard seabed is limited. However, these formations are not indestructible; storms, cyclones, and sand movement can lead to the erosion or burial of exposed peat.
Scientists continue to study how much carbon these deposits store and how they change over time. Researchers believe that similar reefs may exist in other parts of the world with coastal peatlands, including Southeast Asia, the Caribbean, and West Africa. However, further research is needed to determine their prevalence.
This study emphasizes the importance of looking beyond conventional coral reefs when mapping and protecting marine ecosystems. Along the Mozambican coast, the remnants of ancient forests sustain life in unexpected ways, reminding us that some of the ocean's most interesting ecosystems have a history that began long before they were submerged.
