Coral Bleaching

What are Corals? 

• A Coral is a living creature that forms reefs
• A Coral’s body is usually clear. The bright colours that characterize many corals are various types of algae growing in the polyp’s tissue, called the Zooxanthellae
•  Zooxanthellae are microscopic algae that reside on coral and have a symbiotic connection (each provides something to the other, and receives something back in exchange)
• Through their photosynthetic functions, Zooxanthellae assist corals in the development of nutrients. They give energy to coral through fixable carbon molecules, increase the process of calcification, and aids in regulating the flow of nutrients
• In return, the host coral offers a safe environment for its Zooxanthellae, and also an unending amount of carbon dioxide to support the photosynthetic process
• There are two kinds of corals, soft corals, as well as hard corals. Hard corals constitute reefs
• Tiny creatures known as polyps create coral reefs. The polyps abandon the limestone (calcium carbonate) structures to help in their growth, and development till they die. The new polyps also colonize the limestone
•  In the end, the coral reef is composed of skeletons, which are then being covered with living polyps
• Even though corals are in areas with low nutrient levels, the capacity of corals to reuse nutrients that are scarce (by the entire community of nutrients) is remarkable
• A variety of vertebrates, invertebrates, and even plants are near corals within the coral reef ecosystem, which allows for strong coupling of resources and recycling
•  This allows coral reefs to boast an extremely high level of productivity and diversity, as they are also known as “the Tropical Rainforests of the Oceans”
• While the majority of coral reefs can be located in subtropical and tropical waters, there are deep-water corals that are found in colder areas
• Cold Water Corals: Cold, deep (39-55 degrees Fahrenheit) waters are the home of cold-water corals. As per the United Nations Environment Program, there are more coral reefs in cold water than tropical reefs anywhere on earth. Six distinct coral species are associated with the creation of the reefs
• The Roost Reef, which lies near the shores of Norway, is the world’s biggest Coral reef that is cold water

What is Coral Bleaching?

• Coral is vibrant and colourful due to zooxanthellae, which is a type of microscopic
  algae. Zooxanthellae are in an interdependent relationship within the coral, with each supporting each other in their survival
• When corals feel stressed due to variations in conditions like light, temperature, and nutrients, they shed the symbiotic algae that live within their tissues, which causes them to completely turn white
• This is called coral bleaching
• Coral bleaching is the process by which corals turn white as a result of various stressors such as temperature, light, or nutrient changes
• When coral polyps expel the algae (zooxanthellae) that live inside their tissue, the coral turns white. 

What are the causes of coral bleaching? 

•   The primary reason for coral bleaching is the effect of climate change
• A warming planet leads to ocean warming, and a change in the water temperature as small as 2 degrees Fahrenheit (ca. -17 °C) can cause coral to die off algae
• Coral bleaching can occur for various reasons, including extreme shallow tides and pollution or excessive sunlight
• Climate change is turning carbon dioxide into heat for the oceans and is causing corals all over the globe to bleach
• It’s already caused more coral bleaching across the globe and is expected to grow in severity and frequency over the next few decades
• The burning and mining of coal emits carbon dioxide into the air and is warming our oceans and warming our planet
• If we keep polluting our ocean and air by releasing carbon dioxide at the rate we do, coral reefs all over the globe will be facing danger in the next decades, possibly within our lifetime
• There are two reasons for  Coral bleaching: natural causes, and diseases.

Natural causes

Natural causes that lead to the bleaching of coral are as follows:

• The rise in sea temperature
• The majority of coral species are found in water close to the highest temperature they can tolerate, i.e., even a tiny increase in temperature in the ocean could hurt corals
• El Niño elevates the sea temperature and damages coral reefs.

Ocean acidification

In response to an increase in carbon dioxide levels, oceans take in much more carbon dioxide. This causes an increase in the acidity of ocean water and hinders the coral’s ability to build calcareous skeletons that are vital for their survival.

UV and solar UV radiation

The changes to tropical patterns cause less cloud cover and more radiations that cause coral bleaching.

Infectious Diseases

Permeation of bacterium such as vibrio shiloi hinders photosynthesis of the Zooxanthellae. These bacteria are more powerful with increased temperatures at sea.

Chemical Pollution

The increased concentrations of nutrient compounds impact corals through the promotion of phytoplankton growth, which then supports the growth of amounts of species that compete with corals for space.

Increased sedimentation

The clearing of land as well as coastal construction results in high erosion rates and a higher concentration of silt suspended particles, which could do the following:

• Corals are smothered when particles disperse (sedimentation),
• Reduced light availability (turbidity) and
• Possibly reducing coral photosynthesis as well as development.
• Subaerial exposure

Rapid exposure of coral reefs flats to the atmosphere during extreme events like extremely low tides or ENSO-related sea-level drops, or tectonic uplift could cause bleaching.

Freshwater dilution

Rapid dilution of the reef’s waters due to storm-generated run-off and precipitation has been shown to trigger coral bleaching.The majority of the time, these bleaching events are uncommon and restricted to tiny, nearshore areas.

Anthropogenic causes

(Human causes) caused by chemical pollution (pesticides cosmetics, pesticides, etc.), industrial pollution, mechanical damage, the loading of nutrients or sediment and shipping, dredging tourism, mining or collection, thermal pollution-intensive fishing, etc.Recent rapid declines in coral reefs are believed to be due primarily to human-caused impacts (overexploitation of the reef, overfishing, more sedimentation, and nutrient overloading.

Security Measures

• The Ministry of Environment and Forests offers financial assistance to Union Territories/ Coastal States to help with coral reef and mangrove guarding and maintenance
• It is listed as Schedule I of the Wildlife Protection Act of 1972 which grants it the highest degree of protection that is possible
• Protected Areas, which include protected areas, including Three Marine Biosphere Reserves, 96 Sanctuaries as well as National Parks, have been created across the United States to protect marine life, including coral reefs, as per the laws in the Wildlife (Protection) Act, 1972
• The Wildlife Crime Control Bureau was created to enhance the enforcement of laws to fight poaching and the illegal trade in wildlife.