- Coral reefs are one of the major parts of the marine ecosystem. Calcium Carbonates are the main component of corals and bound of coral polyp colonies are responsible for the making of reefs. They grow in shallow and clear water and are found basically all over the tropical region.
- Coral reefs are the home of an unidentified number of marine species. As the Great Barrier Reef, it provides suitable habitat for approximately 1,500 fish species, more than 400 coral species, and about 4,000 mollusc species, besides these some threatened species like Sea cows, Large Green Turtles, etc. are also found in this area. The Coral Triangle is another example of the vast Marine ecosystem and it is a coral-rich marine region which is situated around Indonesia, Papua New Guinea, the Philippines, the Solomon Islands, Malaysia, Timor-Leste, and covered a roughly triangular-shaped area.
- Coral reefs are very important and valuable Resources for human beings. It also provides a security shield of coastlines from cyclones.
- Due to Global warming, the average temperature of the earth has increased. Over the last hundred years, the earth has warmed drastically, especially over the last 2 decades. There are many causes behind it. Some are natural and some are man-made.
- Maximum sunlight is absorbed by greenhouse gases. The excess heat which is absorbed by the earth also increases the temperature of the ocean water and makes it acidic in nature, thus it directly affects the ocean ecosystem and marine Species. Global Warming is also a threat to the ecosystem of coral reefs due to thermal stress.
- It is also proved that due to global warming, the rates of Coral calcification have declined and the rate of coral bleaching has increased.
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.
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.
Impact of Global warming on Coral Reefs
1. Bleaching
- When corals lose their natural colour and become white, it is called coral bleaching.
- There is an algae named Zooxanthellae that lives within coral (symbiotic relation) and both of them are thermal sensitive. It helps each other to survive. But on account of global Warming, the temperature of the ocean has been increasing. As a result coral stresses out. It expels algae and become white. Once the coral died, the entire ecosystem become destroyed.
- According to a report, 20% of the tropical coral reefs died due to heat stress.
- Example- Coral bleaching has been observed in the Great barrier reef of Australia, Andaman & Nicobar.
- According to the recent data 2021, Okinawa is the largest reef of Japan, in which 80% of corals died due to bleaching.
2. Fluctuations in mineral composition of ocean
- There are many minerals present in the ocean water, such as magnesium, calcium etc. On account of global warming the ratio of the minerals in ocean water become disproportionate. As a the ratio of those minerals that helps to survive the corals, also lose their proper balance.
- Example- coral reefs of Caribbean Island collapse owing to mineral imbalance.
3. Nutrients
- Many coral reefs have unique relation with an algae, called Zooxanthellae. It live within the coral polyps. They use sunlight and produce sugar for generating energy. They transfer the energy to the coral. Instead of this, coral transfer carbon dioxide to the algae. This algae is very sensitive to the temperature. Due to Global warming, the average temperature of ocean is increasing day by day. As a result Zooxanthellae are decreasing gradually.
- The another main nutrients for the corals are phytoplankton. It leaves maximum in the subtropical region. Due to the increase of temperature phytoplankton are decreasing.
4. 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.
5. 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.
6. 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.
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