Many of the once-magnificent corals in our oceans are dying. A global-scale change on our blue planet is dulling previously colourful reefs, and killing off countless organisms.

Coral reefs are underwater ecosystems that are formed using calcium carbonate structures. They are built by and made up of thousands of tiny animals – clusters of polyps – which have small tentacles and produce colourful pigments, responsible for giving the coral its various colours. Those that do not have tentacles to grab small fish and plankton, obtain their nutrients from  zooxanthellae – tiny in-house algae that convert the sun’s energy to food via photosynthesis.

In recent years, the decline of coral reefs has entered the spotlight, causing panic among environmentalists and marine scientists. Among all the coral reefs in the world, WWF (World Wildlife Foundation) has reported that out of the corals reefs found in 109 countries, severe reef degradation has been found in 93. Without human intervention, over 60 percent of the world’s coral reefs will be gone indefinitely.

The current global coral bleaching event has sparked action from many conservation groups, which are pointing the finger at those in power who are failing to make the necessary eco-adjustments. Recently, the 2016 International Coral Reef Symposium concluded with a pressing letter to Australian Prime Minister Malcolm Turnbull highlighting the urgency to save the Great Barrier Reef from rapid bleaching. Above all, the Australian Government was heavily criticised for their lukewarm approach towards protecting the reef’s fragile ecosystems.

Mass Bleaching

Bleaching occurs when stressors such as pollution and elevated water temperature cause corals to expel their zooxanthellae, turning the corals completely white. No algae means no food for the coral. Though it is not necessarily life threatening, it is a sign that the corals are under tremendous stress, and if conditions don’t normalise, it can ultimately result in death.

Not all bleaching incidents are due to warming waters; there have been instances where unusually cold water temperatures have resulted in corals being bleached. According to reef biologists working in the waters of the Florida Keys National Marine Sanctuary, during the first two weeks of January 2010, the plunge in water temperature caused the death of many of its Montastrea corals. These boulder-sized slow-growing corals – likely over a century old – had survived past bleaching events and hurricanes.

Currently, the Great Barrier Reef has seen 93 percent of its corals bleached. This is a direct result of the El Niño phenomenon warming water in the Pacific Ocean, and leaving only 68 of the reefs untouched. The scale of this bleaching  could escalate drastically due to the formation of fewer clouds and a higher level of UV radiation blasting the corals.

"When water temperatures are too high the algae start to produce free radicals which damage the coral. If temperatures do not return to normal soon, and the coral reabsorb the algae, it will likely die." © XL Catlin Seaview Survey

“When water temperatures are too high the algae start to produce free radicals which damage the coral. If temperatures do not return to normal soon, and the coral reabsorb the algae, it will likely die.” © XL Catlin Seaview Survey

Human-Based Threats

Coral reefs have endured for millennia, powering through years of earthquakes and tsunamis, only to be heartlessly destroyed by careless fishing practices and unregulated commercial tourism.

Common examples of destructive fishing practices are bottom-trawling and the use of poison and underwater explosives. Bottom-trawling is a customary industrial fishing method to catch as many fish as possible by dragging enormous nets along the sea floor. Along with sea creatures, corals get ripped off the reefs and accumulate in the nets. Coral and other unwanted species are thrown back into the ocean – “discards” that  can reach up to a shocking 80 to 90 percent of the catch.

Cyanide is used to capture live fish for the viewing aquariums and the restaurants of Hong Kong, Singapore and mainland China. The poison only stuns the fish, making them easier to catch. However, its already-lethal formula mixed with water becomes even more toxic, killing marine organisms, including corals, and turning these “rainforests of the sea” into barren deserts. The practice is banned in many countries across Asia, but in Philippine waters, for example, it is reported that an estimated 65 tons of cyanide are poured into the ocean yearly.

Dynamite fishing is the indiscriminate killing of fish from the shockwaves of exploded bombs. The blasts demolish various reef structures and wipe out many of the organisms. It takes a few hundred years for a reef to rebuild and time is not on our side. Though the number of illegal fishing cases has declined in the Philippines, the country’s fishing bureau estimates that there are still around 10,000 dynamite fishing incidents every day.

Coral mining is a profitable business; corals are used in the construction industry where coral pieces fill roads and are even made into bricks. Sand and limestone from coral reefs are ingredients to make cement. In addition, corals are harvested for calcium in the manufacture of health supplements, and are collected to be made into ornamental souvenirs. The continuous removal of rocks means that corals cannot attach themselves to a permanent structure. As such, drifting corals are left to rot away on the seabed. Corals are much more than attractive playgrounds for divers and underwater photographers. A coral reef provides a barrier against waves, storms, floods and even tsunamis. Healthy reefs have rugged, rough surfaces that provide friction to attenuate the speed and magnitude of the rolling waves caused by underwater earthquakes.

"Coral reefs have endured for millennia, powering through years of earthquakes and tsunamis, only to be heartlessly destroyed by careless fishing practices and unregulated commercial tourism." © Wikimedia Commons

“Coral reefs have endured for millennia, powering through years of earthquakes and tsunamis, only to be heartlessly destroyed by careless fishing practices and unregulated commercial tourism.” © Wikimedia Commons

Consequences of Dead Coral Reefs

A future without these multicoloured reefs is looking more and more like an unavoidable consequence for ocean enthusiasts, marine biologists and researchers.

Coral reefs are the core components of the marine world – nearly half of all fish live in them and depend on them. If they disappear, common species like groupers and snappers will become a thing of the past, elevating fish to a luxury gourmet cuisine.

The economic damage following the demise of our coral reefs would be a tragedy. Commercial tourism from the hotels to water-sports businesses targeting tourists would suffer financially because there will be no more underwater experience to enjoy. Not to mention, pharmaceutical companies are constantly finding cures for cancer, heart diseases and viruses using the reefs, create tonics and painkillers. In short, they are our hope to advance medical science.