Coral reefs are termed the "rainforests of the sea," these fragile ecosystems, covering less than 1% of the Earth's surface, support approximately 25% of marine species. They provide vital shelter, breeding grounds, and sustenance for marine life, contributing to oceanic ecosystem health. Additionally, coral reefs act as natural barriers, protecting coastlines from erosion and storm damage, and ensuring the safety of coastal communities and infrastructure.
These Coral reefs are under severe threat from climate change, which brings rising sea temperatures, ocean acidification, and extreme weather events. Elevated temperatures trigger coral bleaching, as corals expel their essential symbiotic algae, resulting in stress, color loss, and increased vulnerability to disease, potentially leading to the decline of entire reef ecosystems. Moreover, ocean acidification, stemming from increased carbon dioxide absorption, impairs coral calcification, weakening their skeletons and making them more susceptible to damage.
Coral bleaching is a phenomenon where coral reefs lose their vibrant colors, turning ghostly white. This discoloration is a visual representation of the coral's deteriorating health. This phenomenon is caused primarily by rising sea temperatures and environmental stressors.
These invaluable ecosystems, often referred to as the "rainforests of the sea," are facing an existential threat.
Consequences of Coral Bleaching
1. Decline in Coral Health
The most immediate effect of coral bleaching is the decline in the health of individual corals. When corals lose their symbiotic algae, they lose their primary source of nutrients, making them weaker and more susceptible to diseases. In severe cases, bleached corals can die, leading to a rapid loss of live coral cover on reefs.
2. Loss of Biodiversity
Coral reefs are among the most biodiverse ecosystems on the planet, providing a habitat for countless species of fish, invertebrates, and microorganisms. When coral reefs suffer from bleaching, the entire ecosystem is disrupted. Many marine species, including those that rely on corals for food and shelter, are adversely affected, which can lead to a decline in biodiversity.
3. Coastal Protection
Coral reefs play a critical role in protecting coastlines from erosion and storm damage. Their living organisms, along with their calcium carbonate skeletons, act as natural barriers that absorb and dissipate the energy of incoming waves. This reduces the impact of storms and helps prevent coastal erosion, safeguarding communities and valuable infrastructure along coastlines of oceans.
4. Economic Impact
Coral reefs have significant economic importance, particularly in coastal regions. They support fisheries that provide food and livelihoods for millions of people worldwide. Moreover, coral reefs are major attractions for tourists and divers, contributing significantly to the economies of many coastal communities. The loss of coral reefs due to bleaching can have devastating economic consequences for these regions.
Causes of Coral Bleaching
1. Elevated Sea Temperatures
The primary and most significant cause of coral bleaching is the rise in sea temperatures due to climate change. Corals have a delicate symbiotic relationship with microscopic algae known as zooxanthellae. These algae reside within the coral's tissues and provide them with essential nutrients through photosynthesis. However, when sea temperatures exceed a certain threshold, the corals expel these algae, leading to the loss of their vibrant colors.
2. Ocean Acidification
Another major factor contributing to coral bleaching is ocean acidification. As our planet's carbon dioxide levels increase due to human activities, the ocean absorbs a substantial portion of this excess CO2. This leads to a decrease in the pH levels of seawater, making it more acidic. The acidic environment puts additional stress on corals, making them more susceptible to bleaching.
3. Pollution and Runoff
Water pollution from various sources, including agricultural runoff, sewage, and industrial waste, can introduce harmful substances into coral reef ecosystems. These pollutants not only harm the corals directly but also promote the growth of harmful algae i.e. Eutrophication, which can outcompete the corals for space and resources.
4. Overfishing
Overfishing can disrupt the delicate balance within coral reef ecosystems. When key herbivorous species are overharvested, macroalgae and seaweed can proliferate and smother the corals. This deprives them of vital sunlight and space, increasing their vulnerability to bleaching. According to Central Marine Fisheries Research Institute (CMFRI) data, fish catch in Maharashtra has risen since 2017, increasing by around 38% from 1.23 lakh tonnes in 2021 to 1.7 lakh tonnes in 2022.
5. Physical Damage
Physical damage to coral reefs, often caused by human activities such as anchoring boats or reckless diving, can leave corals wounded and more susceptible to infection. Damaged corals are also less resilient to environmental stressors, including temperature changes.
6. Disease Outbreaks
Coral diseases can quickly spread through a reef, affecting multiple colonies. These diseases, often brought about or exacerbated by stressors like elevated temperatures, can lead to widespread coral bleaching events.
Coral bleaching is a critical issue with severe and widespread consequences. The health and survival of coral reefs are integral to the well-being of marine life and coastal communities. By addressing the root causes and consequences, we can work towards safeguarding these invaluable ecosystems.