In early April, Rohan Arthur and his colleagues working in the Lakshadweep suddenly saw a large number of fish dying off the island of Kalpeni. They counted at least 10 different species of fish floating up dead to the surface. This triggered an alarm for the scientists. They noted on these still and calm days in the first week of April, sea surface temperatures were soaring at 35 degrees Celsius.
“That was unheard of. I had rarely encountered conditions like that,” said Arthur, who is with the oceans and coasts programme of the Nature Conservation Foundation. “By about 33 degrees, oxygen starts becoming limiting for most fish. What we were witnessing in the reefs in those three or fours days were fish essentially just struggling to breathe and suffocating in water.”
The fish deaths and high sea surface temperatures signaled disaster for the network of coral reefs in the Lakshadweep and sure enough, Arthur found corals starting to bleach in the beginning of April. The threshhold for corals before they start bleaching is around 30 degree Celsius. The bleaching should only get worse since May tends to be warmer than April and the cooling monsoons still one-and-a-half months away. The scientists are anticipating that when they are finally able to assess the reefs in September and October they will find widespread damage.
Corals are actually clusters of thousands of marine animals called polyps. Tiny algae that live in the tissues of polyps provide corals their nutrition and colour. When there is a disruption in the coral’s ecosystem, like water becoming too warm, polyps expel their algae and the corals turn white – the phenomenon called bleaching. If algae don’t return to the bleached corals, the corals die.
Coral bleaching is taking across the world this summer, with a monstrous El Nino and an attendant patch of hot water in the north Atlantic heating up ocean currents for a large chunk of the past year. The Great Barrier Reef in Australia has been devastated with 93% of the reef having been bleached by the off-the-chart sea surface temperatures. Bleaching has also been recorded at several reefs of the coast of Australia between the cities of Darwin and Broome.
The current bleaching in the Lakshadweep is doubly dangerous for the reefs because it comes smack in the middle of a recovery from a 2010 bleaching event. The Lakshwadeep reefs have been hit by severe bleaching events in 1998 and in 2010. In 1998, the world first woke u to the possibility that climate change was affecting ocean currents and creating global El Ninos that affected coral reefs around the world. Massive coral bleaching around the world had everyone thinking that coral reefs may be extinct by 2030.
The corals turned out to be made of far sterner stuff. In Lakshadweep, Arthur documented the recovery in the Lakshadweep. “Between 1998 and about 2005-2006 there was a brisk recovery and by about 2008 some parts of the reef had recovered almost 100 percent of what they had lost in 1998. For me it was a very positive sign that the reefs had much more resilience than I gave them credit for.”
Arthur was expecting to see the same bounceback in after the bleaching of 2010 but that has unfortunately not happened.
Tuna fishing help conserve coral
The previous reef recoveries have been aided by sustainable fishing practices on the islands, where the dominant fishing industry is that of tuna, which is not a reef fish. Unlike trawling and large-scale netting off the mainland India, Lakshadweep fishermen have mostly only used a pole-and-line method of catching tuna fish from surface waters between the islands. This ensures that there is no overfishing and also protects the reef, said Mahima Jaini, a researcher with the Dakshin Foundation.
“The only thing they take from the reef are the bait fish. That has relatively little impact because they have very short lifespans, mature fast and reproduce fast,” she said.
But, Jaini notes, that the fishing industry has been changing with growing reef fishery. Fishermen have told Jaini that foreign and mainland vessels have been coming in harvest tuna with long lines and bigger nets, and that local fishermen have to go out farther and spend longer on fishing expeditions.
There are many things that are needed for corals to recover. New coral recruits need to grow that must come from some coral that has survived bleaching. The new recruits need to attach to a substrate in the ocean, which depends on how much algae and how many herbivorous fish there are in the waters. Algae, left alone, grows and takes over all possible surfaces. Fish, like parrot fish and surgeon fish, feed on algae keeping it in control and making sure that there are surfaces that coral recruits can settle down on.
The coral recruits, once they settle, must be allowed to grow undisturbed. If any one of these factors breaks down, that delays coral recovery significantly.
“The reefs are not doing as well as I expected them to do, and this time around if we see bleaching and mortality like anything that I expect to see, it is going to set back that recovery process as well. So what normally takes about 10 years to recover may take 15 or 20 years,” said Arthur.
Why the Lakshadweep coral reefs are important
The Lakshadweep islands are low-lying coral atolls, ancient volcanoes that have sunk below the sea. The coral forms a ring around islands and protects the islands from the open sea. Arthur compares the corals to a cement factory that is constantly building a wall around the islands, protecting their inhabitants. When bleaching destroys corals, it’s like the factory shuts down and the processes of the sea break down the protective wall.
Without the wall the islands, in whose lagoons you find calm waters even during the worst monsoon storms, are exposed to the ocean and erosion. Erosion put pressure on the land in the tiny islands that house 70,000 people.
The people in Lakshadweep depend directly and indirectly on the reefs for their food. The third danger is that once the ramparts of the reefs are broken increasing amounts of seawater could enter freshwater supplies on the islands. The islands are only habitable because of available potable water and contamination of even some of these groundwater sources by disease to make island evacuation a very serious contention. “Once you don’t have freshwater to drink, you are looking at the scenario where you have to evacuate 70,000 people from the archipelago,” said Arthur.
Arthur worries that the people of Lakshadweep, who are all educated, from the middle class, will have to join an underclass on the mainland of India. “That I think would be a human catastrophe.”
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