Coral bleaching
Date: 31 March 2022 Tags: Climate ChangeIssue
Australia’s Great Barrier Reef is experiencing a mass coral bleaching event, the management authority has announced.
Background
The Great Barrier Reef is the world’s largest coral reef. It is located on the east-coast of Australia.
Details
The current bleaching event is the sixth bleaching event that has occurred and fourth one in the last six years.
Coral reefs
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They are invertebrates that are made up of individual animals known as polyp. Multiple polyps form colonies called reefs.
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The Great Barrier Reefs of Australia stretch across 2,300 km. They sustain an ecosystem consisting of multiple corals, fishes and mollusc.
Types
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Corals are two types--hard corals and soft corals. Hard corals extract calcium carbonate from sea water to build exoskeletons.
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Soft corals attach themselves to these skeletons. Over the years, they add their own skeletons to form coral reefs.
Existence
Corals share symbiotic relationship with single-celled organism called zooxanthellae. They provide corals nutrients and in turn in they get place to live.
Coral bleaching
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It is an event in which the coral polyps expel colour-giving zooxanthellae. This exposes their white exoskeleton, giving it a bleached appearance.
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Due to changing temperature, ocean acidity or pollution, corals experience stress. In such a condition, the algae produce reactive oxygen compounds, resulting in their expulsion.
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The events are temporary or permanent based on the amount of stress. If the stress conditions subside over time, the algae can come back and their symbiotic relationship survives.
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If it remains for a longer time, algae do not return. The corals do not receive their food and nutrients, which results in their destruction.
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Studies have shown that 14% of the world’s corals have died between 2009 and 2018 due to coral bleaching events.
Significance
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Coral reefs take a small amount of space but they support 25% of marine species such as fish, turtles, lobsters etc.
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Coral reefs are the backbone of fishing industry as they sustain large fish population. Large fishes are also dependent on smaller fishes.
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They have $2.7 trillion worth economic value due to goods, services and tourism related activities. They protect protection over sea storms.
Status of Great Barrier Reefs
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Climate change has threatened existence of the reefs. Future bleaching events can destroy the remaining reefs in Australia.
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The UNESCO had threatened to degrade World Heritage Site listing, after which Australia created “Reef 2050” plan to protect the site.