The Bar Reef in Kalpitiya, once a glorious coral reef is now in a feeble state with live coral cover down to about one percent. It was struck by a severe coral bleaching event last year, the worst after 1998, according to specialists in marine environment.
The major coral bleaching event was caused by the El Niño and La Niña effect in 2015-2016. A similar catastrophe occurred in 1998, but the Bar Reef could bounce back over time. Can it do the same again? As the marine experts portray, the chances are bleak this time around. The coral reef has a challenging time ahead recovering on its own, given the increasing impact of human activities and climate change.
Corals are dead all over again
The Bar Reef located about two kilometres off the coast of Kalpitiya was declared a Marine Sanctuary in 1992. It stretches parallel to the coast from the northern end of the Kalpitiya Peninsula, to the islands which separate Portugal Bay from the Gulf of Mannar. Being one of the country’s most diverse marine habitats, it is the most famous and the largest coral reef in Sri Lanka.
International Union for Conservation of Nature (IUCN) Coastal and Marine Program Coordinator, Arjan Rajasuriya, who examined the Bar Reef two weeks back, told the Sunday Observer that almost 99 percent of the corals in shallow waters to a depth of about 5-6 metres were dead.
“It will take at least 15-20 years for the destroyed corals to come back, but only if this bleaching occurrence did not take place repeatedly.
However, with climate change, it is likely that these occurrences may happen regularly,” said Rajasuriya, who had previously worked as a Research Officer at the National Aquatic Resources Research and Development Agency (NARA)for over 27 years, specializing in coral taxonomy. “The Bar Reef was very badly bleached last year, basically, in the period April to June, and when we visited this time we discovered that the reef has not recovered and most of the damaged corals have now become rubble. In the sea, everything loose is moved by wave action and currents. The damaged corals have accumulated due to wave action and rolled over the other corals. The bleached corals have not had time to recover because of the movement of this coral rubble,” he explained.
He noted that the restoration of coral beds by replanting is not possible, given the large scale destruction. “When acres and acres are destroyed, how are you going to restore, and where would you get live corals to do that?” he questioned.
He also pointed out that the reef structure should remain unharmed for the new coral larvae to settle. “In the event in 1998, the reef structure was largely intact because it was the first large-scale bleaching occurrence. This helped new coral larvae to settle. When it happened this time, the reef structure was weak. Now, it has turned to rubble,” he added.
Coral reefs absorb wave energy
Coral reefs act as a natural barrier in the coastlines by breaking up waves, thus reducing the waves’ force. It provides protection against coastal erosion and even Tsunami, by acting as a buffer. The absence of the coral reef will leave coastal communities more vulnerable to natural hazards.
Above all, coral reefs are home and breeding grounds to many fish species, big and small. The destruction of reef will be a financial blow to thousands of families depending on fishery and the ornamental fish industry for their livelihood.
“When the corals get affected most of the fish disappear and then fisheries is affected. If we try to fish the same way as before, the fishing pressure in the area will increase.
This will lead to fishermen resorting to destructive fishing methods, more and more. Even now, we could see them laying nets on the damaged reef causing further damage. In a large scale coral bleaching scenario like this, we should not be fishing in those areas,” Rajasuriya warned.
El Niño and La Niña
According to scientists, El Niño events are associated with a warming of the central and eastern tropical Pacific, while its reverse effect, a sustained cooling of these same areas, is called the La Niña. La Niña results in warmer than usual sea surface temperatures in the region north of Australia. “This is what causes bleaching. When that happens there is mass die-off of corals. This is not specific to Sri Lanka. For example, more than 500 km of the Northern part of the Great Barrier Reef in Australia have been largely destroyed by this event. Likewise, many islands in surrounding areas have also been affected,” Rajasuriya added.
He explained, it was during the La Niña period, which happened about six months after the El Niño, that Sri Lanka’s coral beds were affected.
The IUCN officer observed that the coral reefs along the Western and Southern coasts of the country were badly affected last year, while the East coast did not suffer much because of the wind pattern and atmospheric conditions.
What happens during bleaching?
| The reef is now under threat. We do not know the future of it |
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According to marine biologists, the corals lose their colour and turn white during coral bleaching that happens as a result of extreme temperature differences, pollution or other such reasons. The 2016 and 1998 coral bleaching events were due to sea surface temperature increasing to a level that corals cannot tolerate.
“Most corals contain algae called ‘Zooxanthellae’ and it provides nutrients to the corals. When sea water is too warm, corals expel the algae living in their tissues and this is what causes the corals to turn white. This is called coral bleaching. When a coral bleaches, it is not dead. Corals can survive a bleaching event that lasts for a short period. There had been a number of similar instances between 1998 and 2016. When the bleaching event lasts for a long period, then the mortality of corals is high,” explained Prasanna Weerakkody, Marine Research Team Leader of the Ocean Resources Conservation Association (ORCA).
Reduce human impact
He said, the Bar Reef had a chance of recovering in post-1998 due to minimum human impact in the area during the time of war. “The 1998 bleaching event basically killed about 50 percent of the corals of the South and West coasts of Sri Lanka and the Bar Reef was also caught in that. Live coral cover before the bleaching was something like 80 percent and it dropped to about 5 percent.At that time the Bar Reef was a much larger reef with many pieces of patch reef connected together. In post-1998 only very few patches recovered, but they recovered well. Certain sections of the Bar Reef recovered almost perfectly and gained about 90 percent live coral cover within a decade from 1998-2009 due to the remoteness of the reef when the war was on. This chance of recovery was not there for the southern reef and as a result places like Unawatuna and Hikkaduwa did not recover properly,” he elucidated.
Right now, the Bar Reef has faced a challenge in recovering because the live coral cover even in the few patches that survived after 1998 has dropped to about one percent.Added to this, there is now a lot more human impact, such as, fishing pressure, dynamiting and the use of ‘laila’ and ‘surukku’ nets, ornamental fish collection, tourism and pollution.
“The reef is now under threat. We do not know the future of it. For proper recovery we need to let the reef be at peace. Let it recover on its own by reducing the human impact. The coral reef is going to have a very difficult period recovering and it is not going to recover if we add our own pressure over it,” Weerakkody cautioned.
The Marine Biologist further said, they could see that the reef was heavily overgrowing with algae dwindling its surviving chances further. “Agricultural runoff and pollution from the land could have contributed to the large amount of algae growth on the reef. The key point in reef recovery is the availability of live corals surviving on the reef. When the surviving coral percentage is very low survival chances are much less. Last time, there was about 5 percent live coral cover, but this time it is even less,” he remarked.
He, however, expressed that there is a chance of repopulation through larvae arriving from somewhere else. “Another option of recovery is the arrival of live coral larvae from places like the Maldives, through currents. For that to happen, coral reef surfaces have to be in a state where the larvae can settle in. At present, there is far too much algae. Algae prevent anything settling in,” he added.