Wenzel Pinto has watched the reefs he is studying lose their vibrant orange over the past year.
The wildlife biologist has been posted in Lakshadweep since 2020. Diving to study reef conditions is part of his job as a research assistant with the NGO Nature Conservation Foundation (NCF).
“Every single colony across the 2,000-sq-metre Goniopora patch perished as I watched,” he says. “I saw the tissue sloughing off the skeletons, and algae smothering the remains.”
India has five major reef structures along its coasts: at the Gulf of Mannar in Tamil Nadu, the Gulf of Kutch in Gujarat, the Andaman and Nicobar Islands, the Malvan coast of Maharashtra and parts of Goa, and Lakshadweep. They were under immense strain even before the recent heat waves and mass-bleaching events.
Illegal harvesting once posed a major threat and so, as with tigers and elephants, corals are protected in India under Schedule 1 of the Wildlife Protection Act, 1972. They cannot be harvested, bought or sold.
Other stressors emerged, in the form of marine pollution from effluents and oil, bottom-trawling (using towed nets to catch fish close to the seabed), blast-fishing, reef-fish harvesting, and steady infrastructural development along the shoreline. Now, the heat is stepping up threat levels.
Heat-wave durations in the Indian Ocean are expected to grow from about 20 days a year (between 1970 and 2000) to about 220 days a year by the end of the century, according to data from scientists with the Indian Institute of Tropical Meteorology (IITM) and National Institute of Oceanography (NIO), among others.
Efforts to preserve the Indian reefs have largely consisted of restoration programmes in which coral fragments are moved to protected underwater “nurseries” or to artificial reefs. But most of these efforts have focused on the dominant family of reef-building coral species called Acropora. They grow and calcify the fastest. But they are extremely sensitive to temperature.
This means that, as temperatures rise, India’s artificial reefs can be expected to bleach and die too.
Shape-shifting
Lately, there have been efforts to branch out.
NCF is monitoring bleaching sites and will be using the data gathered to identify refugia: areas that will be most hospitable to coral, as ocean temperatures rise. “These reef refugia may either remain cooler during the bleaching events, through upwells from cooler deep waters or local current systems, or the coral there may have evolved to deal with the high temperatures,” Pinto says.
Already, this kind of evolution is altering how reefs look.In Lakshadweep, colonies of Acropora are being replaced by the more heat-resistant Porites family. Species like Porites are expected to become more dominant, as the intervals between bleaching events shrink.
The algae that inhabit coral tissue, giving them their colour and their nutrition, are changing too. Corals in Lakshadweep are increasingly hosting Clade D, a more resilient zooxanthella found in abundance in the Gulf of Kutch.
That gulf could provide more clues to the way forward.
“The marine fauna here are exposed to high surface temperatures during low tide for a long time, and research on how they have adapted could help map the way forward,” says Deepak Apte, a marine biologist and director of the not-for-profit Srushti Conservation Foundation.
What we urgently need is a holistic canvas of comparative data from the various reefs in India, he adds. “Data is currently scattered across various institutes. We need a centralised pool so we can determine, together, how to carry out restoration efforts more efficiently.”
A rainforest without its trees
It’s important to act soon, the researchers agree. These marine ecosystems, without the corals, will be the equivalent of a forest without trees.
Exposed sites like coral atolls will face the worst impacts. These are coral reefs that have essentially isolated a stretch of saltwater from the sea, and become completely exposed at low tide. The Lakshadweep archipelago is home to 12 such atolls.
“The islanders who live there are dependent on the reef for protection from storm surges and cyclones, for fishing and for tourism. The death of these reefs could eventually make these islands uninhabitable,” Pinto says.
Planning the next phase scientifically will be vital, Apte adds. “We can try new methods, but they should not end up like our tree-planting drives, which are not always planned or executed scientifically.”
Meanwhile, the hope is that global efforts will slow the overall warming. Which still wouldn’t save the reefs, Pinto says, but would give us more time to work something out.
