The coral bleaching phenomenon
The beautiful coral reefs surrounded by blue tropical seas are not just coloured rocks but are thriving ecosystems with live corals that attach their skeletons to rocks and live there. The colours indicate the presence of single-celled algae-like zooxanthellae within their tissues that provide them with the essential nutrients through photosynthesis and in turn, the corals provide them with the required carbon dioxide and ammonium (NOAA, 2017)
Even though reefs cover only a tiny area of the oceans (less than 0.1 per cent) they support the survival of almost a quarter of the marine creatures and over 500 million people on the planet (Underwater Earth, 2015) who are dependent on it for food, fishery, livelihood and culture.
In the last two decades, the corals around the globe have been experiencing massive bleaching, wherein they lose their colours and turn pale / white as they are unable to support the algae within them because of changes in sea water temperatures (very high or very low), high solar irradiance (too much of light), lowering of nutrients and salinity due to too much of surface run-off or mixing of fresh water near the coast, overfishing, heavy storms or pollution (oil drilling/spilling, coral trading, chemicals in agriculture, marine activities).
Figure 1. The various stages of coral bleaching
Source: Great Barrier Reef Marine Park Authority, 2017
Corals can survive without the algae for short periods and revert back to original health with the re-entrance of the algae once the sea conditions return to normal, but if the stress factors stay longer, the corals begin to starve and die. The coral reefs, eventually, collapse due to erosion. A healthy coral reef system can even resist coral bleaching, but increasing global warming and frequent episodes of bleaching weaken even the healthy reef systems.
Global Extent of Coral Bleaching and Clive Wilkinson Report
Mass coral bleaching and mortality has become a global phenomenon covering all oceans. The first global event was observed in 1998 due to an underwater heat wave of a great magnitude triggered by El-Nino conditions (warm current spreading fromÂ Pacific to Indian Oceans), resulting in the death of about 16 per cent of the coral reefs around the world. And before the reefs could recover fully, the second mass bleaching event occurred in 2010.
Within just 4 years, the world saw the longest mass coral bleaching ever from 2014-2017. In the Great Barrier Reef of Australia (that runs for almost 4,000 kilometers along the north-eastern coastline) which is one of the best managed marine protected areas in the world, among the 500 observed reefs, only about 4 did not experience any bleaching in 2016 (hitting about 90 per cent of the reefs, and killing between 29 – 50 per cent of the reefâ€™s coral) (Underwater Earth, 2015).
Figure 2. Coral bleaching in various locations globally
Source: Underwater Earth, 2015
Clive Wilkinson Report
The first report on the â€˜Status of Coral Reefs of the Worldâ€™ was published in 1998 by the Global Coral Reef Monitoring Network, edited by Clive Wilkinson. Since then the report was published regularly (2000, 2002, 2004 and 2008) with updates on reef status in different regions and countries of the world, including- Indian Ocean, Asia and Australia, Pacific Ocean, the Caribbean, Atlantic Ocean and South America with contributions from scholars of different countries. The reports predicted that almost all the reefs would soon be coming in the threatened stage (NOAA Coral Reef Watch, 2017).
The initial report focussed more on pollution, over-fishing and other human stresses to corals, however, the increasing frequency, scale and the severity of the events led scholars to conclude that coral reefs are one of the first ecosystems where the impacts of unexpected global warming and ocean acidification are clearly visible to everyone around. Rather, these are just the beginnings of a human-ecological crises waiting to snowball and require strong protective measures to preserve the biodiversity as well as local life systems.
Coral Reefs in India
Coral reefs are found in the Lakshadweep and Andaman and Nicobar Islands, Gulfs of Kutch, Mannar and Khambat, Malwan Reef and Angria Bank (Maharashtra) and Netrani Island (Karnataka). A May 2016 news report by S. Dasgupta has revealed that Indian coral reefs are experiencing massive coral bleaching and death mainly due to heat stress and population pressure, increasing inundation and making the scarce fresh water unfit for consumption, especially in low-lying atolls like- Lakshadweep (S. Dasgupta, 2016).
Figure 3. Coral Reefs in India
Source: ESSO, Government of India
What is Being Done To Protect Coral Reefs?
There are as such no standard or strict laws to protect the reefs globally, but there are many alliances and organizations likeâ€“ Global Coral Reef Monitoring Network, International Coral Reef Initiative (ICRI), National Oceanic and Atmospheric Administration (NOAA) â€“ which are involved in preventing damage to healthy reefs and restoring damaged ones through assessment, conservation and restoration programmes (that include- coral nurseries, marine protected areas and awareness campaigns) world-wide involving local communities.
In India, Panini, in her paper titled â€œLaw and Policy for Conservation and Management of Coral Reef Areas in Indiaâ€, states – the coral reefs come under the ecologically sensitive areas (Coastal Regulation Zone, CRZ-I) and Wildlife Protection Act. So, no new activities related to construction/ underwater blasting/ use of corals or sand from beaches are permitted. There is a National Committee on Wetlands, Mangroves and Coral Reefs, but it has no strict policies that stop harmful activities or pollution on the seaward side (Panini, FAO, 1997).
Immediate reductions in CO2 emissions, overfishing, sedimentation and pollution, and promoting sustainable tourism and education are the only ways to save reefs from vanishing completely.