Goa corals wilt under El Nino warmth
Soaring temperatures have made 2016 one of the hottest years on record. A climatic phenomenon, known as El Nino, is carving a destructive path through the Indian Ocean, slowly warming the waters. Research scientists studying the temperature anomaly say the vital coral ecosystem, just recovering after the 2010 El Nino, is taking a fresh beating.
Though the extent of coral damage will be known only after the monsoon, corals of Australia’s Great Barrier Reef appear to have borne the brunt of it. Researchers have also noticed that the corals around the atolls of Lakshadweep are showing signs of succumbing to the warming waters.
“The El Nino of 2016 comes at a time when the Lakshadweep reefs are starting to recover. Bad as that event was, it pales in comparison to the extent of bleaching we are currently seeing. The 2016 El Nino event is likely to be a major banner year for the Lakshadweep reefs, with potentially large-scale and irreversible declines of reefs across the archipelago,” marine ecological scientist at the Nature Conservation Foundation Rohan Arthur, said.
Goa has a miniscule presence of coral reefs around Grande Island archipelago just off the coast of Vasco. A large trove of corals has been found mid-sea off the Konkan coast by the scientists of the National Institute of Oceanography ( NIO ) known as Angria Bank. But, since the corals are much further away from the equatorial line, researchers have not focused their study on these sites.
What is worrying scientists is the frequency at which the corals are being affected by temperature disturbances. “Corals harbour colorful symbiotic algae called zooxanthellae, which use photosynthesis to produce nutrients for themselves and their hosts. When the water gets too hot, the corals expel the zooxanthellae and turn white, a process known as bleaching. If the water cools soon enough, the algae return. But prolonged bleaching can kill the corals,” physical oceanographer and physicist at NIO Prasanna Kumar, explains.
The symbiotic cells on corals contain chlorophyll and provide nutrients to the corals in exchange for protection. To ensure a continuous source of necessary nutrients, the coral regulates the number of zooxanthellae cells and chlorophyll amount.
An NIO team of 11 researchers has set up an instrumentation suite at Agatti, Laskhswadeep Islands, to study temperature, salinity, solar radiation, chlorophyll and ocean currents.
“More than the rise in temperature, the decline in chlorophyll and variation in carbon dioxide levels in the ocean are bigger threats,” Kumar said.
Like the trees in a forest, corals provide the basic habitat and structure for a reef. Among the corals thrive a variety of marine species that make the reef a diverse ecosystem. When a coral dies, a rapid decay sets in, leading to dramatic declines in the species.
Researchers Mathew Koll Roxy, Aditi Modi, S Prasanna Kumar, M Ravichandran and others jointly authored a research paper, ‘Reduction in marine primary productivity driven by rapid warming over the tropical Indian Ocean’. While stating that the western Indian Ocean hosts one of the largest concentrations of marine phytoplankton blooms in summer, the research report highlights that the same region has witnessed the largest warming trend in sea surface temperatures in the tropics during the past century.
“The current study points out an alarming decrease of up to 20% in phytoplankton in this region over the past six decades. We find that these trends in chlorophyll are driven by enhanced ocean stratification due to rapid warming in the Indian Ocean. Future climate projections suggest that the Indian Ocean will continue to warm, driving this productive region into an ecological desert,” the research paper states.
As much as it is denied, man-made global climate change is at the heart of the issue, but the mismatch between political self-interest and preservation of the environment remains.
