What are the coral reefs and their role in nature? - Seeker's Thoughts

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What are the coral reefs and their role in nature?

Coral reefs are home to 25% of all marine life on the planet. In fact, the variety of life supported by coral reefs rivals that of the tropical forests of the Amazon or New Guinea.

 But without urgent action to address climate change, pollution, overfishing and other threats, these beautiful and life- sustaining organisms could disappear.

The Great Barrier Reef has experienced a third mass coral bleaching event in five years, according to the scientist carrying out aerial surveys over hundreds of individual reefs.

Global heating caused by escalating atmospheric greenhouse gases is a major threat to the world’s coral reef ecosystems. 

The UN’s Intergovernmental Panel on Climate Change found the published evidence suggested a majority of tropical coral reefs would disappear even if heating was limited to 1.5C and would be “at very high risk” at 1.2C. 

The globe has warmed about 1C since the industrial revolution.

The latest mass bleaching comes as Unesco’s world heritage committee is scheduled to assess the reef’s status this year. 

It is the first time the committee will have considered the natural wonder’s world heritage status since the back-to-back bleaching events.

A team lead by Dr. Shanmugaraj found an alarming pattern of bleaching in the reefs in Mandapam, Keezhakkarai and Palk Bay. 


The sea surface temperature ranged from 28.7°C to 31°C in the August 2018-February 2019 period and there was no bleaching seen then.

However, when the temperatures rose to between 32°C and 36°C between March 2019 and May 2019, researchers observed a pattern of bleaching in corals, which was different at different layers within the sea.

What is coral reef?

A coral reef is an underwater ecosystem characterized by reef-building corals. Reefs are formed of colonies of coral polyps held together by calcium carbonate. Most coral reefs are built from stony corals, whose polyps cluster in groups.

Where does coral reef found

About 12% of coral species observed at depths between 0m and 2m such as Porites solida, Poritis lutea, Montipora digitate, Acropora hyacinthus were completely bleached. 

About 5% of species observed at depths between 2m and 4m such as Acropora formosa, Acropora hyacinthus, Montipora digitata, Montipora foliosa, Pocillopora damicornis, Goniastrea retiformis, Platygyra sinensis, Dipsastrea favus, Dipsastrea speciosa were partially bleached.

Coral reefs are also found in the deep sea away from the continental shelves, around oceanic islands and as atolls. Most of these ocean coral islands are volcanic in origin. The few exceptions have tectonic origins where plate movements have lifted the deep ocean floor on the surface.

Porites species observed in Palk Bay region were completely bleached at depths from zero to 4 metres. Corals at depths over 5m did not face bleaching.

Coral reefs are home to 25% of all marine life on the planet. In fact, the variety of life supported by coral reefs rivals that of the tropical forests of the Amazon or New Guinea. But without urgent action to address climate change, pollution, overfishing and other threats, these beautiful and life- sustaining organisms could disappear.

When a coral bleach, it does not die but comes pretty close to it. Some of the corals may survive the experience and recover once the sea surface temperature returns to normal levels.

Coral reefs are important hotspots of biodiversity in the ocean. Corals are animals in the same class (Cnidaria) as jellyfish and anemones. 

They consist of individual polyps that get together and build reefs. Coral reefs support a wide range of species and maintain the quality of the coastal biosphere. 

Corals control the level of carbon dioxide in the water by converting it into a limestone shell. If this process does not take place, the amount of carbon dioxide in the ocean water would increase significantly and affect ecological niches.

How are the corals formed?

Coral reefs were formed after the last ice age when melting ice caused the sea level to rise and flooded the continental shelves.

This means they are less than 10,000 years old. As coral reef communities were established on the shelves, they built reefs that grew upwards, keeping pace with the rise in sea level. 

Reefs that did not keep pace became drowned reefs, covered by so much water that it was insufficient for light to penetrate in to water and reach up to the coral reefs. As coral reefs also need the sunlight for photosynthesis. 

Though polyps do not photosynthesis, but it is done by the red algae which takes shelter in exoskeleton of polyps. So, it is understood that coral reefs show a symbiosis relationship (a relationship which benefits both the species). 

Why coral bleaching should be a matter of concern?

This symbiosis relationship is very important. Factors like climate change, destructive fishing practices, rising temperature, disturbance in water, pollution and acidic rain hamper this relation between polyps and red Algae. 

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Due to the strain polyps throw the red Algae out of the exoskeleton. When red Algae is out which is the food creator in the process of photosynthesis goes out and polyp don't get efficient food. When the red Algae leaves the coral reefs, losing its colour and this is called the coral bleaching.

Importance of Coral Reefs

Coral reefs are important for many different reasons aside from supposedly containing the most diverse ecosystem on the planet.

They protect coastlines from the damaging effects of wave action and tropical storms.

They Provide habitats and shelter for many marine organisms. They assist in carbon and nitrogen fixing in ocean. They help with nutrient recycling.
Coral reefs also work as huge carbon sink that means they impact positively on greenhouse gas- Carbon dioxide.

The study of coral reefs is important for providing a clear, scientifically-testable record of climate events over the past million years or so. This includes records or recent major storms and human impacts that are recorded by the changes in coral growth patterns.

What are the main threats to coral reefs?

Coral reefs have survived tens or thousands of years of natural change, but many of them may not be able to survive due to human destruction.

One-quarter of coral reefs worldwide have already been damaged, another two-third also are under serious threats. there are various factors which disturb the coral reef formation and some of them are given below: -

1-Climate change – Constant change in climate is a major cause of coral reefs disruption. Corals cannot survive if the water temperature is too high. Global warming has already led to increased level of coral bleaching, and this has been predicted that coral reefs will be more threatened or perhaps will not survive at all. This again will lead to further chaos

2-Destructive fishing practice- Unsustainable fishing practices cause further harm like coral blast or dynamite fishing, bottom trawling, and banging on the reef with sticks. Bottom- trawling is one the greatest threats to cold-water coral reefs.

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Pollution – Water pollution is one among the major reasons of disturbing the ecological environment of coral reefs.  urban and industrial waste, sewage, agrochemicals, and oil pollution are poisoning reefs. These toxins are dumped directly into the ocean or carried by river system from sources upstream. Some pollutants, such as sewage and runoff from farming, increase the level of nitrogen in seawater, causing off their sunlight. as nitrogen helps in the rise of Algae bloom that means the Algae covers the surface of the water that stops sunlight from going in to water. this means photosynthesis will be hampered in to water ecosystem.

Conservation of coral reefs

Coral reefs are fragile ecosystems. As these are very sensitive about their environment. Their importance does not stand up to the fish and oceanic ecosystem, human gets various fishes which edible due to coral reefs. Therefore, if all the parameters of climate are taken in to consideration, this is predictable that in upcoming time the human population will rise.

They will need more food which includes the heavy diet of fishes. Another aspect is the coral reefs maintain the healthy ecosystem of ocean, tempering with coral reefs may impact water cycle and the oceanic health which again may turn the living atmosphere of the earth into something very bad.

There may be another chaos like coastal erosion or water can be cloudier. so, it is hard to predict that what will be the exact consequences, but conservation of coral reefs is very important. 

Scientist are working to preserve coral reefs- in some parts they have been constructing unique artificial reefs to rehabilitate the coral reefs in damaged area.

Artificial reefs are designed primarily for providing habitat for marine wildlife.

LMMA or locally managed marine protected area can play a healthy role in conservation of coral reefs 

The International Conference on Status and Protection of Coral Reefs 

The International Conference on Status and Protection of Coral Reefs (STAPCOR – 2018) is being held at Bangaram coral Island of Territory of Lakshadweep.

Theme: “Reef for Life”

Organizers: It was jointly organized by Department of Environment and Forest, Union Territory of Lakshadweep Administration with the technical support of Zoological Survey of India (ZSI) and in association with Ministry of Environment, Forest and Climate Change (MoEFCC), International Union for Conservation of Nature (IUCN), Environmental Information System (ENVIS) in  with declaration of year 2018 as 3rd decadal International year of Reefs.

What is STAPCOR?

The effect of climate change and global warming along with El-Nino on the corals has led to heavy bleaching internationally during the year 1998

This led to the foundation of STAPCOR with a decision to have a international conference in every 10 years to review the status and progress of coral reefs all over the world

The goals of the 3rd IYOR – 2018  are: 
1.       Strengthen awareness about ecological, economic, social and cultural value of coral reefs and associated ecosystems.

2.      Improve understanding of the critical threats to reefs and generate both practical and innovative solutions to reduce these threats.

3.       Generate urgent action to develop and implement effective management strategies for conservation and sustainable use of these ecosystems.

The first IYOR was designated in 1997 in response to the increasing threats on coral reefs and associated ecosystems. The hope was to increase awareness of the value of and threats to coral reefs, and to promote conservation, research and management efforts on a global scale.

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