Tropical rainforests of the sea, under threat!

Coral reefs in the Andaman Islands (Image Source: Ritiks via Wikimedia Commons)
Coral reefs in the Andaman Islands (Image Source: Ritiks via Wikimedia Commons)

Coral reefs are said to be one of the most valuable ecosystems on Earth and harbour a wide range of animals and plant species. They are often referred to as the 'Tropical Rainforests of the Sea' because of their uniqueness and the richness of biodiversity that they harbour, and the wide range of economic and environmental services that they provide to millions of people through fisheries and tourism, besides protecting shorelines from storms and other natural hazards.

What are corals

Corals are large group of invertebrate animals called Cnidaria that occur in a wide variety of colours, shapes and sizes. They have a simple stomach with a single mouth that is surrounded by stinging tentacles. Each individual animal is called a polyp, and polyps live in groups to form colonies through a process of budding, where the polyps grow copies of themselves.

Corals can be classified into hard and soft corals. There are around 800 species of hard corals, also known as the ‘reef building’ corals. Hard corals extract calcium from surrounding seawater and use this to create a hard structure around them for protection and growth. Coral reefs are thus created due to millions of tiny polyps forming large carbonate structures, that provide a home to hundreds of plant and animal species. The calcium carbonate structure is crucial to maintain the functionality of the corals.

Soft corals, on the other hand, include seas fans, sea feathers and sea whips, and do not have the calcium carbonate skeleton like hard corals. Soft corals also live in colonies, that look like brightly coloured, feathery plants or trees that hang down in order to capture food floating in the currents. 

The corals share a symbiotic relationship with single-celled algae, known as zooxanthellae and exchange oxygen and other gases and nutrients to survive. This contributes to the brilliant colours of the corals. Light is crucial for survival of corals and this makes corals highly susceptible to environmental stress.

Under threat and vanishing rapidly!

Coral reefs are under serious threat, and global warming due to climate change is the culprit. A recent study published in the journal PNAS has estimated the impact of the two greatest threats to coral reefs namely, ocean warming and acidification on 183 reefs located in 233 locations of the globe.

Ocean warming can lead to coral bleaching and the corals can die because of bleaching over long periods of time while ocean acidification can make it difficult for coral reefs to grow their calcium carbonate skeletons. 

The study predicts that majority of the coral reefs will unable to maintain their calcium carbonate production levels - crucial for maintaining their hard skeletal structure while continuing to experience losses due to physical, chemical, and biological erosion, in the years to come.

The study also finds that anthropogenic climate change related processes are already preventing the accretion (vertical growth) of the corals at majority of the sites and bleaching events are responsible for this erosion.

The study finds that the highest decline in coral reefs has happened in the Atlantic Ocean (49 percent), followed by the Indian Ocean (39 percent) and Pacific Ocean (11 percent). This can be a great threat for a large amount of organisms that live in the oceans and depend on the reefs for food and also humans who depend on them for their livelihoods, warns the study.

Coral reefs in India

India has a coast line of nearly 8129 kmts with coral reefs found in abundance at the Gulf of Kutch; the Gulf of Mannar; Lakshadweep Islands and the Andaman and Nicobar Islands.

A recent review published in the International Journal of Fisheries and Aquatic Studies informs that there are three major types of reefs, namely the fringing reefs that are attached to the shore and grow towards the sea, found in Andaman and Nicobar Islands and Gulf of Mannar; Barrier reefs, separated from the mainland or island shore by a lagoon and found in the Andaman and Nicobar islands and the atolls,  circular or continuous barrier reefs found on the Lakshadweep islands.

Corals, hotspots of biodiversity

Andaman and Nicobar islands have the largest stretch of coral cover in India with 89 percent of India’s coral diversity seen in these reefs. The reefs include 1284 species of fish, 3271 species of molluscs, 765 species of echinoderms, 519 species of sponges, 345 species of coral belonging to 87 genera, 607 species of crustaceans and 624 species of algae.

Importance of corals

Corals support livelihoods: Coral reefs are vital for fisheries as they  provide nurseries for the ocean's fish, and are a rich source of protein and generate revenue for local communities.

Corals can cure: Coral reefs are of great medicinal value and can be useful for curing life-threatening diseases such as cardio-vascular diseases, ulcers, leukemia, lymphoma and skin cancer. The unique skeletal structure of corals is useful for making bone-grafting materials.

Corals can build: Coral Reefs are rich in limestone which is often used as a cement substitute in the construction industry. At an industrial level, the coral sand rich in calcium is also a potential raw material for the cement industry.

Coral reefs act as protective barriers: Reefs act as natural barriers and protect coastal cities, communities, harbours and beaches from ocean waves and prevent erosion, property damage and loss of life. Corals reefs also help in maintaining quality and clarity of shore water as they are filter feeders and consume particulate matter suspended in the water. Corals control carbon dioxide levels in the ocean by using  dissolved carbon dioxide to form new reefs.

Threats to coral reefs

Ocean acidification: Anthropogenic activities and human interventions have led to increase in atmospheric concentrations of carbon dioxide leading to ocean acidification, which has led to decline of calcification rates of corals.

Coral disease: Epidemic diseases such as White plague, White pox, White band, and Black ban have caused extensive damage to coral reefs in India. Recently, prevalence of white band, white pox, white plague, pink line, pink spot, yellow band, fungal blotch, black band, narcotic patches and coralline lethal orange disease (CLOD) have been found in Indian reefs.

Reef fishing: Illegal and destructive fishing practices such as overfishing, blast fishing have led to a decline in herbivorous fish who depend on algae present on the reef. This has led to excessive algal growth on the reefs and led to deterioration of the reefs.

Exposure to predators: Coral reefs in India have also been affected by predators such as coral eating Crown of Thorns Starfish and bio-eroding coral boring sponges.

Natural calamities: Cyclones, earthquakes and tsunamis can also lead to destruction of coral reefs.

Uncontrolled tourism: Can damage shallow water corals by leading to unintentional or intentional trampling and breakage.

Anthropogenic activities: Illegal collection of shells, uncontrolled harvesting, smuggling of exotic marine organisms and products from the reefs is a major problem in India.

Efforts in India for conservation of reefs

Baswapoor and Zareena Begum in their Working paper inform that the coral reefs of India come under the jurisdiction of the Department of Forests and Wildlife and The Ministry of Environment and Forests has the authority to issue guidelines for their sustainable utilisation. The management of coral reef ecosystems has also been affirmed in India's National Conservation Strategy and Environment Action Plan.

A few laws exist in the country for the protection of coral reef areas such as the Environment (Protection) Act, 1986 and the Wildlife Protection Act (WPA), 1972. 

The Coastal Regulation Zone (CRZ) Notification (1991) offers the only legal protection to all the coral reefs in India and under this coral reef areas come under the CRZ1 category. A special category, CRZ4 has been prepared for the Andaman, Nicobar and Lakshadweep islands.

There are 36 marine protected areas (MPA) in India, of which 5 are for the conservation of coral reefs. These include Gulf of Mannar Biosphere Reserve; Gulf of Kutch Marine National Park; The Mahatma Gandhi Marine National Park (MGMNP) also known as the Wandoor Marine National Park in the Andamans; The Great Nicobar Biosphere Reserve and the Rani Jansi Marine National Park (RJMNP) in Ritchie‟s archipelago in the Andamans.

The laws are however very vague and difficult to implement. The corals outside the purview of MPA's are not included in the WPA. It is therefore difficult to take action against offenders outside the national park. Recently, the National Committee on Mangroves and Coral Reefs, the Ministry of Environment and Forests, Government of India has set up the Indian Coral Reef Monitoring Network (ICMRN).

Coral Reef Monitoring Action Plans (CRMAPs) were prepared during the first phase of the GCRMN (1997-98) and have been launched by the ICRMN for all reef areas except the Gulf of Kutch. While efforts are on to implement the CRMAPs and train people to monitor the reefs, activities still seem to be in an early stage and the capacity for monitoring and management is still very poor.

Climate change continues to threaten the coral reefs in India that are disappearing at a rapid rate, taking along with them the rich biodiversity and the valuable ecosystem services that they provide. Urgent action to reduce coral stressors and more efforts at reintroduction of species, artificial reef restoration should be a priority to conserve coral reefs in India.