Gulf of Mannar Coral Reef: Protected on Paper

The Gulf of Mannar Coral Reef Is Protected on Paper. What About in the Water?

Published: 12 September 2026

Aerial view of a coral reef surrounding a tropical island in the Gulf of Mannar, India | Ocean Evoke India

Twenty-one small uninhabited islands lie off the Tamil Nadu coast, strung between India and Sri Lanka, each ringed by reef. Together they make up the Gulf of Mannar coral reef, and they are protected about as thoroughly as anything in Indian waters can be: a marine national park, India’s first marine biosphere reserve, a UNESCO listing and a Ramsar site, added in layers between 1986 and 2022.

Live coral cover there has still fallen from 37 per cent in 2005 to 27.3 per cent in 2021.

Those two facts belong in the same sentence, and most accounts of this reef keep them apart. What follows is what each layer of protection actually does, what the monitoring numbers say and how far they can be trusted, and the two places where the paperwork and the water have visibly parted company.

Where the reef is, and what kind of reef it is

The islands sit in four groups, named for the coastal towns they lie off: Tuticorin, Vembar, Keezhakkarai and Mandapam. None of them is inhabited.

The reefs here are fringing reefs. That means they grow directly against the shore or a short way off it, with little or no lagoon of open water in between. That is the most common reef form in Indian waters, and it is why the reef and the island are hard to separate when you look at a map. Patch reefs are also present, meaning small isolated outcrops rather than continuous structure, including at Tuticorin Port and on a formation called Harbour Reef.

So much for the physical picture, which is the part every summary of the Gulf of Mannar gets right. The interesting question is what has been happening to it.

Four designations, and what each one actually does

The Gulf of Mannar has collected protection in layers, and the layers do different jobs.

In 1986 the Government of Tamil Nadu declared the 21 islands and their surrounding waters the Gulf of Mannar Marine National Park under the Wild Life (Protection) Act, covering 560 square kilometres. That figure is a boundary, not a measure of reef. It describes the area inside the line on the map, and a great deal of what is inside that line is open water.

In 1989 the Government of India designated the wider region a marine biosphere reserve, the first in India, and one described as the first in South and South-East Asia. A biosphere reserve is a much larger envelope than the national park inside it, and it takes in inhabited mainland coast. Crucially, it is a designation and a management framework rather than a prohibition.

UNESCO added the site to its World Network of Biosphere Reserves in 2001, which is international recognition rather than domestic law.

Then in 2022 the reserve was listed as a Ramsar site, a wetland of international importance. A Ramsar listing brings recognition and a reporting obligation. It does not, by itself, add enforcement powers on the water.

Four designations, then, of which one is a national park with legal teeth and three are frameworks, recognitions and obligations. The distinction matters for what comes next.

The numbers, and what they do not say

The best condition data for the Gulf of Mannar comes from a decadal monitoring series run by the Suganthi Devadason Marine Research Institute with the Tamil Nadu government, reported by the International Coral Reef Initiative in January 2025.

Live coral cover, meaning the share of surveyed seabed occupied by living coral, stood at 37 per cent in 2005. By 2009 it had risen to 42.9 per cent. By 2021 it had fallen to 27.3 per cent.

The shape of that series matters more than either endpoint. This is not a reef in steady decline. It is a reef that gained substantially, then lost more than it had gained. Reporting only the first and last figures would be accurate in each number and false overall.

Over the same period, mapped reef area fell from 11,060 hectares in 2005 to 6,628 hectares in 2021, and many former reef areas are now dominated by macroalgae or seagrasses rather than coral.

Three qualifications travel with these figures and should not be left behind.

The 27.3 per cent reading is from 2021. It was published in January 2025. Nothing in the available record describes what the reef looks like in 2026, and no later survey figure has replaced it in general use.

No source states how reef area was mapped in either 2005 or 2021. Without a methodology, the 4,432-hectare difference cannot be attributed to a single cause, and it would be wrong to read all of it as physical reef loss when some may reflect remapping or reclassification.

The monitoring and the restoration work in the Gulf of Mannar are led by the same institutional cluster, and the outlets carrying these figures, DT Next among them, are relaying one underlying report rather than measuring independently. None of that is a reason to discard the numbers, which remain the only condition data this reef has. Better to hold them as a single well-documented account rather than as several corroborating ones.

What the mining ban proves

For decades, coral was mined out of the Gulf of Mannar at industrial scale, quarried for limestone and construction material. It stopped in 2005.

What happened next is the most encouraging part of this record. Coral cover rose from 37 per cent to 42.9 per cent in four years. ICRI attributes that recovery directly to the cessation of mining. J.K. Patterson Edward, who directs the Suganthi Devadason Marine Research Institute, told The Wire that the ban “triggered enormous recovery”, and identified it as the single most impactful measure for reef restoration in the gulf.

Now put that against the dates.

The national park was declared in 1986. Hard corals were placed in Schedule I of the Wild Life (Protection) Act in 2001, the highest level of protection Indian law offers, reserved for species given total protection. Mining continued into the mid-2000s and stopped only from 2005.

Roughly two decades passed in which a national park boundary, and then the strongest species protection available, coexisted with the removal of the thing being protected. No source reached explains why enforcement lagged that far behind designation, and it would be irresponsible to guess. But the gap is documented, and it is the first place where the paper and the water come apart.

It also carries an unexpectedly hopeful reading. When enforcement finally arrived, it worked, and it worked fast.

Then the heat came

The recovery did not hold.

The global bleaching events of 2010 and 2016 reversed it. Bleaching is worth explaining precisely, because it is routinely mistaken for death. Coral lives in partnership with algae inside its own tissue. When the water stays too warm for too long, the coral expels them and turns white. At that point it is stressed, not dead. If the heat passes soon enough, it can recover. If it does not, or if the next event arrives before recovery is complete, it does not.

The 2016 event did not fall evenly across the gulf. ICRI reports that reefs in the Mandapam region were more affected than those off Keelakarai and Tuticorin, and peer-reviewed work in Coral Reefs has examined exactly this: resilience differs from island to island within the same gulf, following successive bleaching events. Two reefs a short boat ride apart do not necessarily share a fate.

Heat is not the only ongoing pressure. Marine debris, meaning abandoned fishing gear and other waste settling onto reef, has been documented as a threat here by Mongabay India, and debris removal has been run in these reef areas specifically to reduce stress on already-bleached coral. Destructive fishing and coastal pollution are also part of the picture, though without figures attached in the sources available.

Two decades of restoration, and what four hectares means

The Gulf of Mannar hosts what ICRI describes as India’s earliest and largest coral restoration programme. The Suganthi Devadason Marine Research Institute began work in 2002 and has continued for more than twenty years.

The scale of the effort is real. Over that period the programme deployed 5,550 artificial substrates and transplanted more than 51,000 coral fragments of 20 native species, working across nine of the 21 islands as well as patch reefs at Tuticorin Port and Harbour Reef. Survival of transplanted fragments has been reported between 55.6 and 79.5 per cent depending on location and species, which is a good result by any standard.

The restored area comes to roughly 40,000 square metres. That number is easy to misread.

Forty thousand square metres is four hectares. The reef area mapped in 2021 was 6,628 hectares. Four hectares is about 0.06 per cent of it, or six parts in ten thousand. The two figures come from different measurement exercises and should not be treated as a single clean ratio, but no amount of methodological caution changes the order of magnitude.

That is not a criticism of the programme. Rather, it is a statement about what reef restoration currently is: twenty years of skilled, sustained work by the most experienced team in the country, producing survival rates that would satisfy any practitioner, across an area you could walk in a few minutes. And survival of transplanted fragments is a measure of the programme’s own output. It says nothing at all about the condition of the 6,628 hectares around it.

This reef is not forgotten. Something else is happening.

No. On the evidence, the opposite.

This reef has four overlapping designations, a monitoring series stretching across sixteen years, a restoration programme running continuously since 2002, peer-reviewed literature on its bleaching resilience and on its long-term restoration, dedicated pages at UNESCO and at the Ramsar Convention, and coverage from national newspapers and specialist environmental outlets. Search for it and every result on the first page is an institution, a journal or a national publication. Whatever the Gulf of Mannar is, it is not unwatched.

But the instinct behind the word is pointing at something real, and it is worth relocating rather than discarding.

Two things in this record deserve more attention than they get. The first is that designation ran roughly two decades ahead of enforcement, and the reef kept being mined the whole time. The second is harder, and it is the other place where the paper and the water come apart. The Gulf of Mannar produced one of the clearest conservation success stories available anywhere in Indian waters, a measurable and fast recovery driven by a single enforcement decision, and then lost it to warming water that no marine park boundary can hold out.

This is not a forgotten reef. It is a reef whose best result has been quietly overwritten, which is a different problem and a harder one.

Conclusion

The Gulf of Mannar is the best-documented reef in India, and the best documentation available says that its live coral cover in 2021 was lower than in 2005, despite a national park, a biosphere reserve, two international listings, an effective mining ban and twenty years of restoration in between.

The most useful thing a reader can take from that is a calibration. Local enforcement is not futile, and the 2005 to 2009 recovery is proof that it works, and works quickly. But it operates on a different scale from the thing now driving the losses, and four hectares of restored reef against 6,628 hectares of mapped reef is roughly the ratio between what careful, expert intervention can rebuild and what a warming ocean can take.

There is one more thing worth sitting with. The most recent condition figure for this reef is from 2021, published in 2025. Nobody reading this knows what the Gulf of Mannar looks like today. If the most protected and most studied reef in the country cannot tell us its own condition more recently than five years ago, what should we assume about the reefs nobody is measuring at all?