Threats to Coral Reefs

Key Findings of Threats to Coral Reefs Study

• Ocean Acidification (OA) as a threat to coral reefs: OA is the gradual decrease in the pH of the Earth’s oceans due to the uptake of carbon dioxide (CO₂) from the atmosphere.
  • Reduced calcification: The lower pH of ocean water affects the growth and survival of coral reefs by reducing calcification rates in reef-building organisms i.e. coral polyps.
  • Affects coral reproduction: Coral reefs reproduce by spawning eggs and sperm into the water. When the water is more acidic, the development and survival of coral larvae may be affected.
• Global warming as a threat to coral reefs: The study has found that coral reefs are more affected by global warming-related heat-stress than by ocean acidification.
  • The study also found that the effects of temperature on the metabolism of corals were stronger than the effects of increased CO₂.
  • Coral bleaching: As global warming continues, the frequency and severity of bleaching events will increase, making it harder for coral reefs to recover from these disturbances.
  • Disease outbreaks: High temperatures can also increase the incidence and severity of coral diseases.
  • Changes in storm patterns: This leads to stronger and more frequent storms that can cause the destruction of coral reefs.
  • Sea level rise: This may lead to increase in sedimentation for reefs located near land-based sources of sediment. Sedimentation runoff can lead to the smothering of coral.
  • Reduced growth and reproduction: Increased water temperatures can also negatively affect the growth and reproduction of coral reefs.
  • Changes in coral community composition: High temperatures can cause certain coral species to become more dominant or extinct, altering the composition of coral communities.

Case Study: 2016 & 2017 mass Coral Bleaching in the Great Barrier Reef

• The Great Barrier Reef, located off the coast of Australia, is the largest coral reef system in the world.
• In 2016 and 2017, the Great Barrier Reef experienced mass bleaching events, which were caused by a combination of high ocean temperatures and El Niño.
• Both the events collectively affected almost two thirds of the Great Barrier Reef.

About Coral Reefs

Threats to Coral Reefs Other than Ocean Acidification and Global Warming

• Pollution: Pollution from sources such as agricultural runoff, sewage, and industrial discharges can damage coral reefs by smothering them with sediment, increasing the growth of harmful algae, and reducing the water’s oxygen levels.
• Overfishing: Overfishing can disrupt the balance of coral reef ecosystems by removing key herbivores and predators.
• Coastal development: Coastal development can damage coral reefs by destroying their habitats and increasing the amount of sediment and pollution in the water.
• Unsustainable tourism: Overuse of coral reefs for tourism and recreation can lead to physical damage to the coral, sedimentation, pollution, and overfishing.
• Invasive species: Invasive species such as the crown-of-thorns starfish and the lionfish can damage coral reefs by eating coral and competing with native species.

Stats IQ: Current Scenario of Degradation of Coral Reefs

• In 2019, the Global Coral Reef Monitoring Network (GCRMN) reported that coral reefs have declined by 50% in the last 30 years and it is expected that, this rate of decline could reach 70% by 2030.

Methods to Protect and Restore Coral Reefs

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