In the turquoise waters of the Gulf of Mannar, scientists are piecing together a complex puzzle—rebuilding one of India's most precious marine ecosystems, one coral fragment at a time.
Explore the RevivalThe Gulf of Mannar, nestled between southeastern India and western Sri Lanka, represents one of the most biologically rich marine environments on Earth. Recognized for its extraordinary diversity of species—from vibrant coral reefs to elusive dugongs—this region was declared India's first marine biosphere reserve in 19897 . For decades, human activities and climate change threatened to destroy this underwater paradise. Today, through an ambitious scientific effort, the Gulf of Mannar is becoming a global model for marine ecosystem restoration, demonstrating that even severely damaged reefs can be brought back to life.
Oceanographic research reveals that the Gulf experiences minimal seasonal variations in critical environmental factors like sea surface temperature, salinity, and chlorophyll levels compared to adjacent waters1 .
This unusual stability creates a conducive environment for marine life, particularly for sessile organisms like corals that struggle with fluctuating conditions1 . The region also benefits from its partial sheltering from large-scale ocean circulation patterns by geographical features including Ramsethu (Adam's Bridge) and the chain of islands1 .
Despite its ecological significance, the Gulf of Mannar has faced severe threats since the 1960s, when coral mining became widespread8 . Fishermen and contractors indiscriminately harvested corals for use as building material and calcium carbonate, destroying entire reef structures8 .
The consequences were devastating. By the early 2000s, two islands—Poovarasanapatti and Villanguchalli—had completely vanished beneath the waves, primarily due to the loss of protective coral reefs that had buffered them against erosion3 8 .
Additional islands experienced significant erosion, with studies showing approximately 5.40% of the total surface area of these islands had disappeared since 19733 .
| Island Group | Reduction in Surface Area (hectares) | Percentage Reduction |
|---|---|---|
| Tuticorin | 63.97 | 83.04% |
| Keelakarai | 74.93 | 33.35% |
| Mandapam | 153.92 | 29.60% |
| Vembar | 56.48 | 28.14% |
| Rameswaram | 325.87 | 3.43% |
The restoration team faced a critical challenge: years of coral mining had left the seafloor unstable, with no solid foundation for coral attachment9 . After testing various materials including stones, clay pots, ropes, and cement slabs, they developed specially-designed concrete frames that could withstand strong currents and provide stable attachment points for coral fragments2 9 .
Concrete frames are manufactured on land and transported to restoration sites via barges2 .
Divers arrange the frames on the seafloor, spaced 1-2 meters apart to allow for coral growth2 .
Divers collect 8-12 cm fragments from healthy donor colonies and attach them to the frames using waterproof glue or cable ties9 .
To maintain ecosystem resilience, researchers transplant multiple coral species with different growth forms and environmental tolerances9 .
The two-decade-long restoration initiative has yielded impressive ecological outcomes.
At Vaan Island, one of the primary restoration sites, live coral cover increased from just 2.7% in 2006 to 18.8% by 20202 . In contrast, unrestored sites nearby showed minimal recovery, reaching only 1.8% coral cover during the same period2 .
Perhaps most encouraging has been the resilience demonstrated by restored corals. Despite experiencing bleaching events in 2010 and 2016, the transplanted corals showed better survival rates than their natural counterparts2 9 .
Even more promising, restored corals have begun reaching sexual maturity and exhibiting gametogenic activity similar to wild colonies—a crucial indicator of ecosystem functionality9 .
| Parameter | Vaan Island (Restored) | Unrestored Site |
|---|---|---|
| Live Coral Cover (2006) | 2.7% | 0% |
| Live Coral Cover (2020) | 18.8% | 1.8% |
| Fish Density (2006) | 14.5 (per 250 m²) | Not recorded |
| Fish Density (2020) | 310.0 (per 250 m²) | Not recorded |
| Number of Fish Species | 63 | Significantly lower |
The reef restoration has catalyzed a broader ecological recovery. Fish density in restored areas surged from 14.5 per 250 m² in 2006 to 310.0 by 20202 . Biodiversity measurements recorded 63 fish species at restored Vaan Island and 51 species at Koswari Island, demonstrating the return of a complex food web2 .
Despite these successes, significant challenges remain.
"These reef restoration efforts have shown promising results and have become integral to coral conservation strategy, and gaining international recognition."
The Gulf of Mannar's story demonstrates that human intervention, when guided by careful science and sustained commitment, can reverse ecological damage. The restoration success here provides a replicable model for reef recovery worldwide, proving that even severely degraded marine ecosystems can regain their ecological functions.
The revival of these underwater gardens stands as a powerful testament to what dedicated science and conservation can achieve—offering hope for marine ecosystems everywhere in an era of environmental change.