A crossroads of marine life
The Myeik Archipelago consists of over 800 islands scattered across the Andaman Sea. Geologically, the islands are a mix of granite and limestone, creating a varied underwater topography. This area sits on the northwestern edge of the Coral Triangle, a globally important area for marine biodiversity. Its position is a transition zone, where species from the Indian Ocean meet the incredibly dense life of the western Pacific. For 50 years, the archipelago was closed to foreigners, a period of isolation that ended in 1997 and helped preserve many of its marine habitats.
Comprehensive marine surveys began in 2013 to formally document the region's biodiversity. Researchers from Fauna & Flora International and other groups have identified 495 species of reef fish. The Coral Fish Diversity Index, a statistical model, predicts the total number could be as high as 618 species. The hard coral diversity is also high; one analysis of graduate theses from Mawlamyine University identified a total of 512 hard coral species across 24 of the northern islands. The archipelago has habitats for globally threatened species, including the dugong, whale shark, scalloped hammerhead, and three species of sea turtle green, hawksbill, and leatherback..
An ecosystem under pressure
The reefs of the Myeik Archipelago exist in three distinct forms. The outer islands have fringing reefs on exposed boulder slopes that descend to about 15 meters. Sheltered inner islands, closer to the mainland, have reefs adapted to higher turbidity and strong currents. The third type consists of steep, vertical rock walls on isolated pinnacles that drop to depths of 20-30 meters. Coral cover across these sites varies dramatically, from near zero in some areas to 92% in others.
These ecosystems are characterized by the dominance of massive boulder corals, especially from the genus Porites. The archipelago's waters also support extensive seagrass meadows, which feed dugongs and green sea turtles. Despite the high species count, the ecosystem shows clear signs of human impact. Surveys note a conspicuous absence of sharks and large rays in many areas. While predatory fish like groupers (Epinephelus) and snappers (Lutjanus) are present, larger individuals are found in low numbers, shows overfishing. The most abundant invertebrate is often the long-spined sea urchin (Diadema), whose high numbers shows an imbalance in the reef ecosystem. In 2017, Myanmar designated its first three Locally Managed Marine Areas within the archipelago to give local communities a role in conservation.