Coral Bleaching on the Great Barrier Reef

The Great Barrier reef is currently experiencing coral bleaching due to climate change.

Coral Bleaching on the Great Barrier Reef
(Photo : Twitter)
The Great Barrier Reef aerial view Hughes

One of the seven wonders of the world, the Great Barrier Reef of Australia is great in many ways. A prized World Heritage Area, it is the largest coral reef system and also the biggest living structure in the world- big enough that it can be seen from space.

The Reef is located off the coast of Queensland and composed of 300 coral cays, 600 tropical islands, 760 fringe reefs, and 3,000 individual reef systems. It provides refuge and habitat to an astounding variety of marine life including ancient sea turtles, reef fish, sharks and rays, and 400 hard and soft corals and an abundance of seaweeds.

Now, this marvelous natural wonder is facing yet another threat to its existence- the coral bleaching.

Coral Bleaching

Globally, we are experiencing changes in our average weather conditions and the regularity of extreme events due to the fundamental shifts our climate is undergoing. The Earth's climate is warming and mostly as a result of human activities.

Corals inhabiting tropical coral reefs can only tolerate small temperature ranges since they are thermally sensitive. But due to the changes in our climate that causes abnormally high sea-surface temperatures, coral reefs start to bleach during summer months. As the temperature increases, the intensity of coral bleaching also increases.

Coral bleaching occurs when zooxanthellae coral tissues become transparent and reveal the white coral skeleton underneath it. Zooxanthellae are the tiny, colorful marine algae that live inside the corals and provide them their color and the coral's main supply of energy. But when the temperature rises, the algae die.

The loss of these algae can kill the corals if unfavorable conditions persist. However, when the temperature returns to normal levels, they can regain their zooxanthellae but because of the stress of coral bleaching, its growth and reproduction will likely decrease.

Coral Bleaching from Aerial Surveys       

Coral Bleaching on the Great Barrier Reef
(Photo : Twitter)
Day 5: Reefs northwards from Townsville have extreme levels of bleaching, typically affecting >80% of corals. Awful. Credits: Hughes

In February of this year, temperatures on the reef have reached 1.25C above normal which is the highest on record since 1900. According to scientists the increase in temperature is because the oceans are gathering heat due to accumulating levels of greenhouse gases that are mostly from burning fossil fuels.

Central and southern parts of the reef have accumulated high levels of heat stress based on observations on the reef's conditions from satellites and in-water temperature loggers. But its full effects will only be seen once the aerial surveys were completed at the end of this week, and its data is analyzed.

Three to four years ago- in 2016 and 2017, the Great Barrier Reef has experienced back-to-back intense bleaching that almost killed half the reef's corals. The central and southern parts of the world heritage reef were spared from the impact in those years which means that they are not used to heat and could be hit harder.

The Director of the ARC Centre of Excellence for Coral Reef Studies at James Cook University, Professor Terry Hughes, spent 17 hours in four days doing aerial surveys since last week to score bleaching on reefs along with a staff member from the authority.

Coral Bleaching on the Great Barrier Reef
(Photo : Twitter)
Monitoring and surveying of the extent of bleaching and impacts of heat stress on reef slope communities around Heron Island Page

He found out that corals in Princess Charlotte Bay at the bottom of the Cape York Peninsula had been severely bleached, but the impacts are lesser on the reefs that are located far away from the coast. "Ribbon reefs" of the outer reefs in the north had escaped bleaching.

The corals left during the 2016 and 2017 bleaching managed to survive. Experts are much concerned about what will happen in the southern part, unlike the other two years which impacts are more coastal.

Bleaching does not necessarily mean that the corals are dead, according to Hughes. It is the misconception of many, this only means that the corals need more help. 2016 and 2017 events are considered to be the worst that ever happened to the great barrier reef and if this year would turn out to be less severe, it shall not give us a false sense of security.

Many parts of the Great Barrier Reef are still amazing and beautiful. It just needs us to do more globally and protect it.