Why in News?

• Recently, it is reported that a rapidly spreading disease, commonly known as yellow band disease, is killing corals over vast stretches of the sea floor of Thailand.

What is Yellow Band Disease?

• Yellow-band disease – named for the colour it turns corals before destroying them -was first spotted decades ago and has caused widespread damage to reefs in the Caribbean. There is no known cure.
• The Yellow Band disease is caused by a combination of environmental stressors, including increased water temperatures, pollution, and sedimentation, as well as increased competition for space from other organisms.
• These factors can weaken the coral and make it more susceptible to infection by pathogens, such as bacteria and fungi.
• The disease’s impact cannot be reversed, unlike the effects of coral bleaching.
• Scientists believe overfishing, pollution and rising water temperatures because of climate change may be making the reefs more vulnerable to yellow-band disease.

What are Coral Reefs?

• Corals are marine invertebrates belonging to the class Anthozoa in the phylum Cnidaria.
• They typically live in compact colonies of many identical individual polyps.
• Coral reefs are underwater ecosystems made up of colonies of coral polyps.
• Coral polyps live in a symbiotic relationship with a variety of photosynthetic algae called zooxanthellae, which live within their tissues.
• These algae provide the coral with energy through photosynthesis, while the coral provides the algae with a protected environment and compounds, they need for growth.

Types of Corals:

Hard Corals:

• They extract calcium carbonate from seawater to build hard, white coral exoskeletons.
• They are in a way the engineers of reef ecosystems and measuring the extent of hard coral is a widely-accepted metric for measuring the condition of coral reefs.

Soft Corals:

• They attach themselves to such skeletons and older skeletons built by their ancestors.
• Soft corals are typically found in deeper waters and are less common than hard corals.

Significance:

• Ecological Importance: Coral reefs are one of the most diverse and productive ecosystems on Earth, providing habitat for a wide variety of plant and animal species.
• They also play a critical role in regulating the planet’s climate by absorbing carbon dioxide and protecting coastlines from erosion and storm damage.
• Economic Importance: Coral reefs support a variety of industries, including fishing, tourism, and recreation. They also provide resources for medicine and biotechnology.
• Climate Regulation: Coral reefs act as natural buffers against the impact of climate change by absorbing wave energy, protecting coastlines and reducing the impact of storms and sea level rise.
• Biodiversity: Coral reefs are home to a vast array of marine life, including fish, sharks, crustaceans, mollusks and many more. They are considered as the rainforests of the sea.

Threats:

• Climate change: Coral reefs are particularly vulnerable to the effects of climate change, which is causing ocean acidification and coral bleaching.
• Coral bleaching occurs when coral polyps expel the algae (zooxanthellae) living in their tissues, causing the coral to turn completely white.
• Pollution: Coral reefs are also threatened by pollution, including sewage, agricultural runoff, and industrial discharge.
• These pollutants can cause coral death and disease, as well as reduce the overall health of the reef ecosystem.
• Overfishing: Overfishing can disrupt the delicate balance of coral reef ecosystems, which can lead to the decline of coral populations.
• Coastal Development: Coastal development, such as the construction of ports, marinas, and other infrastructure, can damage coral reefs and reduce the overall health of the reef ecosystem.
• Invasive Species: Coral reefs are also threatened by invasive species, such as the lionfish, which can outcompete native species and disrupt the overall balance of the reef ecosystem.

Initiatives to Protect Corals:

Technological Intervention:

• Cyromesh: Storage of the coral larvae at -196°C and can be later reintroduced to the wild
• Biorock: Creating artificial reefs on which coral can grow rapidly

Indian:

• National Coastal Mission Programme

Global:

• International Coral Reef Initiative
• The Global Coral Reef R&D Accelerator Platform