How Have the Mass Bleaching Events of 2016-2017 Affected the Organisms that Depend on the Great Barrier Reef?

Megan Hyun, Bryce Bottessi, Barbara Trueba, and Robert Robledo


The Great Barrier Reef is an extraordinary natural landmark regarded as one of the seven wonders of the world. Stretching off the Northeastern coast of Australia, it is the most extensive coral reef system of the planet––surpassing 135,000 mi² in size and housing over 3,000 individual reefs, 400 coral types, 1,500 species of fish, and endangered creatures (“Great Barrier Reef”). However, the Great Barrier Reef has been subject to multiple coral bleaching events, the whitening of a coral due to the expulsion of its algae when exposed to warmer temperatures. Among the six mass bleaching events the Reef has experienced, the years 2016 through 2017 statistically proved to be the most damaging.

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Dead coral specimen on Lizard Island, from whitened to covered in algae (XL Catlin Seaview Survey)

How This Issue Impacts Marine Life

Reefs are an incredibly important ecosystem, occupying just 1% of the world’s marine environment (Worland “A Most Beautiful Death”). Despite how little room they take up, nearly a ¼ of all marine species depend on them for survival (“Coral Reefs”). Some use the coral reef for habitation, while others use them as feeding grounds, and to some, they even function as a nursery.

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The Great Barrier Reef supports 25% of all marine organisms (Vlad61)

Some examples of the countless species that rely on the coral reefs for survival include a unique set of thousands of different types of fish, several kinds of turtles, and algae that resides within the coral, whose absence is the cause of the bone white color of the bleached reefs (Worland “A Most Beautiful Death”). These reefs that they so desperately depend on are threatened by a variety of factors, but bleaching is one of, if not the, most prevalent issue at the moment, especially in regards to the Great Barrier Reef. Many of the species listed are in danger of losing their homes if the coral reefs continue to bleach at the rate they have been, and could be lost permanently.

The rising temperatures of the ocean, one of the biggest factors in coral bleaching, has put significant stress on the animals that live within the Great Barrier Reef. Some organisms which are extremely popular among tourists are especially at risk. These include manta rays, clownfish, multiple different kinds of turtles, whales and many more. Biodiversity as a whole is suffering, as coral reefs are one of the most unique habitats with the one of the widest range of species living in it, in the whole ocean.

The bleaching of coral can result in whole communities being wiped out, which would then force any remaining organisms to try to seek food and shelter elsewhere (“Bleaching Impacts”). This could also impact other, neighboring ecosystems that can’t support them. However, the Great Barrier Reef is unique, and many wouldn't be able to find another home that would suit their needs. The whole ocean is impacted by the Great Barrier Reef, as well as other reefs’, bleaching. Not only are a quarter of all marine organisms in serious danger of losing a vital part of their life cycles, but human communities could suffer serious blows as well.

Human Cost

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Australia's Great Barrier Reef has experienced four mass bleaching events in the last seven years, like this one in 2017. Scientists warn repeated bleaching makes it tough for corals to recover.

The Great Barrier Reef provides many important ecosystem services, and plays a crucial role in the daily lives of not just marine organisms, but people as well. They provide many sources of income, including fisheries, tourism, and medicinal products. In fact, the overall estimated economic value for coral reef services worldwide is 3.4 billion dollars (“Coral Reefs Fast Facts”). In Australia alone, the Great Barrier Reef provides about 6.3 billion dollars to the economy, and generates 64,000 jobs (“The Value”).

Coral reefs also play a valuable role in protecting the coastline. It’s estimated that a healthy coral reef can absorb 97% of all energy from a storm, preventing serious flooding and damage caused by large waves (“The Importance of Coral Reefs”). The coral acts as a barrier between the coast and the rest of the ocean, saving thousands of dollars in repairs. However, unhealthy, decaying, and bleached coral can decrease this percentage, and thus make human communities more vulnerable to loss of homes.

Bleached coral doesn’t produce the compounds that scientists often use in their medicinal products as effectively and efficiently as healthy coral. The warming temperatures which cause the bleaching can cause a shift in the fish populations, causing fisheries to suffer from a lack of game (“Bleaching Effects”). The loss of the vibrant colors coral is known for can cause tourists to become disinterested, causing a dip in tourism and a serious loss of revenue. Many people can lose their jobs because of this––which in an extreme case, could lead to economic depression.

What is Being Done About This Issue?

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A diver swims through the coral, videotaping the effects of bleaching. Photo supplied by the Great Barrier Reef Marine Park Authority (GBRMPA)

The Australian government considers coral bleaching as a very real and impactful situation in the ocean. The Reef 2050 Long-Term Sustainability Plan was made to strategize what actions are needed to work towards an end to the negative effects of bleaching (“Reef 2050 long-term sustainability plan 2021-25”). The Australian government also seeks to work with local governments, scientists, landowners, and the community to ensure that the issue is resolved in an effective manner. This plan consists of five main priorities for action.

The first is to reduce the effects of climate change by decreasing carbon emissions. Increasing carbon emissions is a problem that is only worsens as time goes by. Australia plans to not only do this, but also help the community adapt to these changes.

The second goal is to improve water quality by working with local landowners. Sometimes, polluted storm fill can enter the ocean in a process called runoff. This can cause a nutrient surplus in the ocean creating an algae bloom. Which can block their access to sunlight increasing their chance of disease.

The third priority is to introduce strong marine park management to reduce water-based activity impacts. When a loose fishing line falls into the ocean and enters marine environments, it can cause fish to get stuck. This will throw off the balance of an ecosystem, which will eventually affect the coral reefs.

The fourth goal is to reduce outside impacts on the reef. When debris flows from other nations into Australian waters, it will negatively impact the ecosystem. Australia is communicating with other governments in order to decrease the debris that flows into marine habitats.

The fifth and final priority is to protect and rehabilitate marine life living in these reefs. Unfortunately, major damage has already been dealt to these wonderful ecosystems. This is why this priority focuses on helping fix what has already been done to the existing marine life.

Other actions have been taken by the Australian government such as the Reef Trust and the Billion Dollar Reef Protection Package. Both are made to build on top of the major 2050 plan that has already been made. Australia continues to research solutions to the horrible event that is coral bleaching.


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Coral whitening in the Great Barrier Reef. (Laura Richardson/ARC Center of Excellence for Coral Reef Studies/James Cook University)

The Great Barrier Reef is, without a doubt, a pivotal element of our ecosystem. Its importance to our environment is equally as immeasurable as its beauty, providing protection to marine and land life alike, as well as generating profit for the community. Knowing the damages the Reef has taken over the course of the last two decades, it is crucial we raise awareness on the subject and reduce carbon emissions––especially now that it’s suffering a sixth event.


🎓Barbara T. is a junior at CVLCC High in Chula Vista, CA. She is particularly fond of sea butterflies and jellyfish, and her favorite school subject is math. In her spare time, she enjoys spending time at home and watching TV shows.

🎓Megan H. is a junior at McLean High School in Fairfax County, Virginia. She’s been interested in the ocean since the sixth grade, and has always adored visiting the aquarium, particularly to watch the dolphins and the jellyfish. In her free time, she likes to write creative stories, as well as watch cartoons, and create art. Her favorite genre is fantasy.

🎓Bryce B. is a senior at Flextech High School in Novi, Michigan. He has been interested in the ocean and lakes since he was a kid and his parents took him to Lake Huron and has since fallen in love with water. In his free time he enjoys playing chess, baseball and going out with friends.

🎓Robert R. is a senior at Bonita Vista High School in Chula Vista, California. He has a passion for studying marine science and loves to help the environment. During his free time he likes to go to the beach, spend time with friends, and watch T.V.



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