News highlight
The highest levels of coral cover have been recorded in the northern and central parts of Australia’s The Great Barrier Reef.
Key news take away.
- According to the annual long-term monitoring report by the Australian Institute of Marine Science (AIMS), within the past 36 years, the highest levels of coral cover (The Great Barrier Reef) have been recorded.
What are coral reefs?
- Corals are marine invertebrates, the most significant living structures on the planet.
- Each coral is called a polyp, and thousands of such polyps live together to form a colony.
- Corals share a symbiotic relationship with single celled algae called zooxanthellae.
- The algae prepare food for corals through photosynthesis and also give them their vibrant colouration.
- When exposed to conditions like heat stress, pollution, or high levels of ocean acidity, the zooxanthellae start producing reactive oxygen species that are not beneficial to the corals.
- Types of coral:
- Hard corals:
- It extracts calcium carbonate from seawater to build hard, white coral exoskeletons.
- Soft corals:
- Soft corals attach themselves to an older skeleton built by their ancestors.
- It is held together by a jelly-like mesoglea and rigid, spiny structures called sclerites to hold together soft coral polyps.
- Hard corals:
- Australia’s Great Barrier Reef:
- It is the world’s largest reef system stretching across 2,300 km and having nearly 3,000 individual reefs.
- The reef is located in the Coral Sea, off the coast of Queensland, Australia
- It hosts 400 different types of coral and gives shelter to 1,500 species of fish and 4,000 types of mollusk.
- It has been a UNESCO World Heritage Site since 1981.
- Benefits of corals:
- Coral reefs support over 25% of marine biodiversity even as they take up only 1% of the seafloor.
- The marine life supported by reefs further fuels global fishing industries.
- Besides, coral reef systems generate $2.7 trillion in annual economic value through goods and service trade and tourism.
- Coral reefs are said to be the medicine chests of the sea. Some fish that the corals attract, leave behind some chemical compounds that are similar to the ones used in human hospitals.
- The ideal environmental conditions for corals to grow:
- Shallow water:
- Coral reefs need to grow in shallow parts of the water.
- The reef’s surface shouldn’t be more than 80m from the water surface.
- The zooxanthellae need adequate sunlight for their photosynthesis processes.
- Semi-hard or hard surface:
- The semi-hard or hard surface is a precondition for compaction, cementation, and solidification of the coral polyp skeletons.
- Clearwater:
- The beautiful coral polyps perish in areas filled with sediment-filled waters. Moreover, they cease to exist in opaque waters.
- This is because the presence of sediments and opaque water limits the passage of sunlight to the algae that sustain their lives.
- Warm water:
- Coral reefs are directly connected to the warm ocean waters. The temperature of the water must be around 20 degrees.
- Hence, coral reefs generally prevail on the eastern coasts of continents.
- Saline-filled waters:
- The slight salt in ocean waters is extremely important for the development of coral polyps.
- The polyps extract calcium from the waters to protect their skeletons. Hence, mild salinity is a necessity for coral reefs to flourish.
- The threats that push corals to the brink of extinction:
- Global warming:
- Due to global warming, the waters are getting more acidic and posing threats to the coral ecosystem.
- Moreover, the glaciers across the world are melting due to which sea levels are rising.
- Rising sea levels lead to the coral reefs drowning and not getting enough sunlight which leads to their slow growth.
- Coral Bleaching:
- Coral bleaching takes place when the oceans get warmer. Since corals have a narrow temperature tolerance, they get stressed and release symbiotic algae in response.
- When they run out of the algae, they run out of their life source and hence, cease to exist.
- Marine pollution:
- Marine pollution in the form of plastic pollution and other activities has led to the corals being suffocated.
- Coral reefs need air and space to breathe. With the rising levels of sea pollution, we might lose them sooner than we thought.
- Stronger storms and ocean acidification:
- The upsurge of stronger storms has led to oceanic waves that break and damage the coral reefs. They might even break colonies and make them unsafe for living.
- As the sea absorbs more carbon dioxide (CO2), the pH levels increase.
- High pH levels lead to weaker coral skeletons, their vulnerability to diseases and destruction by storms.
- The coral reefs found in India:
- India has mainly four coral reef areas:
- Gulf of Mannar
- Andaman and the Nicobar Islands
- Lakshadweep islands
- The Gulf of Kutch
- India has mainly four coral reef areas:
- The three major types of coral reefs found in India are fringe, barrier and atolls.
- Fringing reefs:
- Fringing reefs evolve and develop near the continent and remain close to the coastline.
- These reefs are separated from the coastline by small, shallow lagoons.
- They are the most commonly found reefs in the world.
- Barrier reefs:
- Barrier reefs are found offshore on the continental shelf. They usually run parallel to the coastline at some distance.
- A deep and wide lagoon is located between the coastline and the barrier reef.
- Atolls:
- Atolls are formed on mid-oceanic ridges.
- They are shaped circularly or elliptically and are surrounded by seas on all four sides and have shallow waters in the centre called a lagoon.
- Fringing reefs:
Pic Courtesy: The Hindu
Content Source: The Hindu