The increase in greenhouse gases in the atmosphere due to human activities causes global warming or climate change. Global warming has increased substantially over the past couple of decades that have led to warming of oceans. This warming has affected the ocean inhabitants including corals.

Also read: What are Coral Reefs?

Threats to Coral Reefs :

• Global coral reefs monitoring network says that 20% of the total coral of the world are already dead. Global warming is the actual  cause behind it.
• According to the DG of UNESCO, the major witness of climate change is coral reefs.
• A report, published by UNESCO says that almost all of the 29 coral reefs, listed by the UNESCO world heritage site, are damaged due to bleaching, and ceased to exist by the end of this century, if the global warming can not be controlled.

Read also:- Protection Measures Of Coral Reefs

Importance of Coral Reefs :

• Coral reefs are said the rainforest of the oceans. It is some of the highly valuable ecosystem of Earth. Scientists estimate that coral reefs support many undiscovered marine species.
• Modern Medical science says that there are possibilities to produce medicine from coral for cancer, arthritis and other diseases.
• According to a report of the National Marine Fisheries Service of US  said that the financial value of coral reefs is almost 100 millions dollars.
• Besides maintaining the marine ecosystems, it also provide jobs and protection from storms. A report said that the value of goods and services from coral reefs is about 2.6 trillion dollars per year on which 36 billion dollars comes from tourism. In 2015, WWF predicted that the climate-related loss on coral ecosystem services will be 500 billion dollars per year by 2100.
• WWF report says that less than 0.2% of the Marine surface area is captured by the coral reefs. But this percentage of coral reefs support the 25% of all the marine Species of the Earth. It directly support more than 475 million people globally.

Read Also: Importance Of Coral Reefs

Impact of global warming on corals:

Bleaching

• Bleaching is a phenomenon where the corals lose their distinctive colour due to loss of zooxanthellae algae. These algae live in a symbiotic relationship and thus their death also leads to the death of corals.
• Eg: Bleaching observed in the Great barrier reef of Australia.

Fluctuations in mineral composition of oceans

• The temperature of oceans regulates mineral contents present in them such as magnesium and calcium. With the imbalance in mineral contents, the corals are unable to utilise these minerals and survive.
• Eg: Collapse of coral colonies in Caribbean islands due to mineral imbalance.

Read Also:- Functions Of Coral Reefs in The Ocean

Nutrients

• The phytoplanktons are a major source of nutrients for the corals. These sustain their lives in optimum subtropical temperatures. Without these organisms, the corals cannot survive.
• Eg: Reduction in phytoplankton in subtropical waters.

Mineral imbalance

• Due to increase in global temperature corals are losing their mineral contents which are useful to sustain the life of corals. 
• Eg:Coral colonies at Carrabian islands are lost due to mineral imbalance.

Infectious diseases

• Bacteria grow in the warm water. Due to global warming, bacterial pathogens, Vibrio Shiloi grows which is harmful for coral.
• 75% death of coral reefs happen due to white band disease.
• There are many fungal diseases which can damage the corals. Aspergillosis is one of such fungal disease. It happens due to a fungus, called Aspergillus sydowii. Besides these, there are some other fungal diseases, such as Dark spots disease, White pox disease etc.

Solar irradiation

• When maximum sunlight reach on the bed of the ocean, it increase stress among the corals. It increase the rate of coral bleaching. It also hamper on coral nutrients because excess solar radiation is made obstruction to produce sugar by the Zooxanthellae.

Cyclones

• Strong wind creates strong weaves. This weaves heavily damaged individual corals and destroy the structure of the reefs. Tropical cyclones may cause highly destruction of coral reefs.
• In 1985 to 2012, 45% coral of Australia died due to cyclone.
• Coral reefs works as a natural barriers in the coastal region. It acts as a buffer and protect the coastal region from the waves and storms that come in from the open ocean.

Way ahead:

• Urgent steps that can reverse global temperatures is the need of the hour. This includes methods like curbing carbon emission, ozone protection etc.
• Reduce the burning of fossil fuel and emission of harmful gases like CO2, NOx, SOx in the atmosphere.
• Reducing pollution near water bodies and the banning of non-biodegradable products near oceans and lakes.
• Artificial reefs can be a solution to stop an island from downing.

Read Also:- Location And Distribution Of Coral Reefs