The Great Barrier Reef: Beautiful blooms to bleached bones

Witness the transformation of the largest coral reef on Earth in a warming world: a journey through climate change

Do we really care so little about the earth on which we live that we don't want to protect one of the world's greatest wonders from the consequences of our behaviour?

- David Attenborough

I | Introduction

Beneath the insolation-rich surface of tropical and subtropical oceans, vibrant life unfolds in the form of coral reefs. These underwater cities teem with an innumerable diversity of marine life and have captivated the interest of explorers and the scientific community for centuries. Composed of intricate calcium carbonate structures, these corals are built by delicate microscopic polyps over millennia. 

These extensive coral reef ecosystems supply both shelter and sustenance for  25% of all marine species , directly rivalling the biodiversity of tropical rainforests. Despite the vast ecological significance provided by coral reefs to both the human and physical environment, they are facing unprecedented threats. This is primarily due to the escalating impacts of climate change. Rising ocean temperatures, caused by the accumulation of greenhouse gases in the atmosphere, are leading to a phenomenon known as coral bleaching.


II | The disappearing colours of our reefs: Understanding coral bleaching

Coral bleaching is a stress response initiated by corals due to changes in their surrounding environment. The most prevalent change that influences these factors comprise large, frequent, and widespread temperature fluctuations which are exacerbated by anthropogenic climate change. This stress response results in the expulsion of symbiotic algae (Zooxanthellae), the corals' primary source of food and the reason for their eye-catching colouration. Without these algae, corals become susceptible to disease and are unable to acquire a sustainable quantity of food to live sufficiently and die after 5 - 14 days if the algae is not repopulated. As the corals die, they leave behind their skeletal white husks - an ocean graveyard, devoid of life and a chilling reminder of the self-conceited nature of humans.


This segment, derived from Sir David Attenborough's ‘Breaking Boundaries: The Science of Our Planet’, highlights the devastating impact of climate change on the Great Barrier Reef, documenting the significant coral bleaching events that have occurred in recent years. The most notable years were the summers of 2016 and 2017, where the reef faced a back-to-back onslaught of heat waves, leading to extensive coral bleaching that devastated  two thirds  of the reef. An area of around 230,000km², a size rivalling the United Kingdom, lost to climate change over the course of two years.


III | Sounding the alarm: Professor Terry Hughes' call to conserve corals

David Attenborough's ‘Breaking Boundaries: The Science of Our Planet’ documentary excerpt additionally introduces Professor Terry Hughes, a highly distinguished marine biologist who specializes in coral reef systems and has based many of his current research within the Great Barrier Reef since the early 2000s.

Some of his notable achievements include his pioneering research on coral reefs as an ecosystem, helping drive the understanding of coral structures and their variations, functions, and resilience to a number of biotic and abiotic factors. In addition, Hughes' expertise on coral bleaching has led him to become one of the leading authorities on the topic. As such, he has subsequently conducted numerous research endeavors to better understand the causes and consequences of coral bleaching, providing comprehensive solutions to assist in mitigating and managing the effects.

An example of this is one of his most recent studies: ‘ Global warming impairs stock-recruitment dynamics on corals ’. During his research, he discovered that the number of coral larvae within the Great Barrier Reef with sufficient capabilities to recruit to new reefs was rapidly declining. He concluded that these findings were in correspondence to rising sea temperatures causing mass bleaching events, leading to the deaths of both adult and more susceptible juvenile corals. In addition to this, the study also showed that coral larvae recruitment on the Great Barrier Reef had declined by 89% in 2018, suggesting that with continued global temperature increase, combined with more frequent and intense mass bleaching events, the Great Barrier Reef and reefs globally would likely collapse by the early 2030s.


IV | Three decades of coral carnage: The human legacy

This comparative map highlights the contrast between mass coral bleaching events on the Great Barrier Reef between 1998 - 2002 and 2015 - 2017. The deeper shades of red, contrast to the lighter shades of yellow, signify more extensive and severe bleaching. Whilst the 1998 mass bleaching event marked the first major occurrence, the more intensive 2017 mass bleaching surpassed all previous records.

The data for this comparison is derived from Dr. Ray Berkelmans' study 'GBR - Coral mass bleaching extent in 1998 and 2002 by aerial surveys', and Dr. Neal Cantin's 'Spatial variability in bleaching severity on the Great Barrier Reef during 2016 & 2017'. These studies induced an incredibly sobering picture following these alarming trends:

  • Over 42% of reefs that compose the Great Barrier Reef were affected by coral bleaching during the 1998 mass bleaching event, resulting in significant coral mortality rates;
  • Whilst not as widespread along the shoreline, the 2002 bleaching event caused twice as much bleaching within offshore reefs compared to 1998;
  • Both bleaching events (1998 & 2002) were directly attributed to prolonged periods of high sea surface temperatures (SSTs), consequence to anthropogenic climate change;

Meanwhile, Cantin's 2015 - 2017 coral bleaching study concluded that:

  • The severity of bleaching on the Great Barrier Reef significantly varied with a strong correlation to heat stress experienced by the corals;
  • Different coral types exhibited different levels of heat tolerance, e.g., branching corals were more susceptible to bleaching than massive corals;
  • Shallower corals experienced more severe bleaching compared to deeper waters. The water depth determined the rate and intensity in which the water around the corals heated;
  • Corals situated in areas of high wave exposure were more severely bleached than areas with less. This was hypothesized as breaking waves dislodging coral polyps from their skeletons; and
  • Nutrient pollution from land-based surface runoff exacerbated bleaching through the promotion of algae growth which compete with the corals for nutrients.

In addition, Cantin's research also found that the severity of bleaching in 2017 was higher than 2016, which was deduced to be a result of the El Niño event that occurred in the same year.


V | Reef Resilience: Securing a future for the Great Barrier Reef

In response to the imposed threats on the Great Barrier Reef, the government of Australia and Queensland developed the ‘ Reef 2050 Long-term Sustainability Plan ’. The plan imposes a comprehensive strategy comprised of long term and short term solutions to manage the reef and ensure its long term health and ecological success. Some key principles highlighted within the sustainability plan include:

  • Reduced greenhouse gas emissions and continual development of adaptive strategies to assist with greater reef resilience to climate change, e.g.,  genetic enhancements to allow corals to withstand a greater breadth of heat fluctuations ;
  • Improvements on the  quality of water  flowing into the reef, including refuse from sewage systems and organic matter produced by surface runoff from farmland;
  • Implementing restrictions to ensure sections of reef remain undisturbed by humans. This includes the instatement of Marine Protected Areas (MPAs); and
  •  Human restoration of the reef,  enacted through a number of different methods. Popular methods include transplanting coral fragments, establishing coral nurseries, artificially seeding reefs with new colonies, and controlling predatory species.

Additionally, the Great Barrier Reef Marine Park Authority (GBRMPA), an institution responsible for managing fishing and tourism, uses and continues to implement strategies to enforce regulations imposed by them. This includes:

  • Quotas and catch limits to mitigate the threat of overfishing and ensuring fish populations do not drop to unsustainable sizes. In addition, encouraging fishers to use environmentally friendly fishing gear; and
  • Education and awareness, teaching tourists who visit the reef about the ecological and global significance of the reef to ensure visitors of the reef are more conscientious when interacting with the reef and surrounding environment.

These regulations from by the GBRMPA, with the support of the Australian government and the worldwide community, have led to a number of positive outcomes for the Great Barrier Reef:

  • Nutrient pollution from terrestrial land use has been reduced by 30% since the issue was highlighted in 2009. This assisted mitigating high turbidity levels, coral bleaching, and increased susceptibility to disease; and
  • Successful control of crown-of-thorns starfish outbreaks. This has been enacted through manual removal, chemical treatment, and thermal shocking - methods that do not adversely effect the reef. As a result of the work from the  GBRMPA , from 2023, over 19 million crown-of-thorns starfish had been removed from the reef.

VI | Is it all doom and gloom? The state of the Great Barrier Reef in 2023

The ' Annual Summary Report of Coral Reef Condition 2022/23 ', produced by the Australian Institute of Marine Science (AIMS) and in collaboration with the Australian Government, provides an insight on the health of the Great Barrier Reef. Whilst there has been little change overall between 2022 and 2023, the report highlights several promising signs of recovery, particularly within the northern and central regions of the reef that have historically been most affected by coral bleaching.

A large player that has contributed significantly to the both the recovery and regrowth of the reef is the fast-growing Acropora corals. These corals are a unique variant as they are particularly resilient to stress and can colonize damaged reef areas quickly. Throughout 2022, the Acropora corals were successful in populating areas of reef that had been damaged due to a relatively mild summer combined with low levels of coral bleaching.

Due to this significant recovery, region-wide hard coral cover within the central and northern regions of the Great Barrier Reef reached between 33% and 36% in 2023. This marked the highest recorded levels since monitoring began 36 years ago.

Despite these significant acknowledgements of improvement on the reef, the report also indicates that the reef remains fragile and heavily dependent on persistent ideal conditions. There are a number of ongoing threats to the reef, both physical and human induced such as crown-of-thorns starfish outbreaks (particularly within the southern region of the reef). In addition, coral disease and bleaching combined with rising sea temperatures create cause for worry in regards to the long-term health of the reef.

Regardless of the challenges presented in the future, these small victories are important and significant as it provides a glimmer of hope for the future success of the Great Barrier Reef. The incredibly resilient nature of the Acropora corals and overall environmental stability of the reef post 2017 suggests that the reef can continue recovering, albeit at its own pace. It is important to remember at such a crucial point for the reef that continuous monitoring is maintained and conservation efforts remain steady to further ensure these small victories are both sustained and amplified to ensure the reef can adapt to the changing climate.


VII | The Great Barrier Reef: A future of uncertainty for one of the world's greatest creations

The Great Barrier Reef is a natural marvel, a true testament to the power of nature and life in one of its most diverse forms; a cacophony of ecosystems delicately balancing the dynamic equilibrium of marine life that has flourished for millennia. From the most miniscule polyp to the largest sea turtle, each creature plays a crucial role in maintaining balance to the reef's overall health and vitality.

It is imperative that we take action to protect the Great Barrier Reef. Reducing global greenhouse gas emissions, improving water quality, and regulating fishing practices are all actions that need to be made now to ensure we have not reached the tipping point and forever jeopardized the reef.

This truth, this responsibility, is a burden we brought upon ourselves as a species, and it is a responsibility we all share.


VIII | Witness the grandeur of the world's largest reef: The indominable spirit of sea life

1

The Great Barrier reef in all its intricacies

Due to the sheer size and complexity of the Great Barrier Reef, the reef has been divided into three distinct regions: the Northern, Central, and Southern Reefs. 

Each region of the GBR contains its own complex and unique biodiversity that face their own set of environmental challenges, each requiring tailored efforts to safeguard and conserve the reef and species that rely on it.

2

The Northern Reef: A story of diversity and resilience

Extending from the Cape York Peninsula to the Torres Strait, the Northern region is the largest and more diverse region.  These warm and pristine waters around the coastline support a vast array of coral species, sponges, fish, and various other marine species . Having its endurance tested by r elentless cyclones, floods, and coral bleaching events , this area of the reef has overall displayed an incredible capacity to recover itself. This has been widely suggested to be caused by its remoteness and minimal impact by humans.

3

The Central Reef: Earth's natural mosaic

Spanning from Cairns to Townsville, the central section of the reef is a culmination of both the northern and southern reefs. Here, the coral reefs are less dense and are far more varied compared to the composition of the northern section. Regardless, this section of reef fosters a rich community. The biggest threats to this region are  sedimentation from upstream rivers , ultimately smothering the coral and rendering the Zooxanthellae within the corals redundant.

4

The Southern Reef: A warm refuge

Extending from Townsville to the southern end of Queensland, this section of the reef is the most temperate. This leads to  restrictions on coral growth as a result of cooler waters . However, the area supports an array of marine species adapted to temperate waters. Despite this, due to global climate change and persistent warming ocean temperatures, this section of the reef is most vulnerable to processes like ocean acidification.

5

The Northern Reef: A new coral discovery

Whilst 2017 was phrased a devastating year for the Great Barrier Reef, there were some exciting news from the University of Queensland (UoQ). Their report stated the discovery of a new species of branching coral within the northern end of the Great Barrier Reef, naming it 'Acropora tenuis'. The coral characteristics comprise a vibrant yellow colour and tree-like structure. The importance of this coral is attributed to its high heat tolerance and ability to grow quickly (see section VI).

6

The Central Reef: Repopulation and new populations

In addition to the discovery in the northern centre, there have also been numerous exciting instances in the central region of the reef. In 2020, the UoQ identified a previously undiscovered source of coral larvae. Located in the Torres Strait, the reefs that comprise this area are a crucial keystone to the entire Great Barrier Reef system.

Furthermore, to combat the ongoing issues with coral loss and bleaching, in 2021 the Australian Institute of Marine Science (AIMS) developed a brand new method to artificially breed coral. Similar to tree grafting, this method uses a technique called ‘coral microfragmentation’, whereby coral polyps are sliced into small polyps and grown in tanks.

Finally, the UoQ has worked tirelessly to identify new corals and species, making a new breakthrough in 2022 where they discovered a species of coral-eating fish. Named ‘Canthigaster rivula’, this small and brightly coloured fish feeds on soft coral polyps.

7

The Southern Reef: The dugong

In mid 2023, researchers from the Australian Marine Conservation Society (AMCS) discovered a previously undiscovered population of dugong within the southern reef. Since this discovery, it has been determined that the dugong population in question may be the largest dugong population in Australia. This is fantastic news for the species, as the dugong is listed ‘Vulnerable’ on the  IUCN  red list, however this information suggests that the population is recovering.

8

Against all odds: Solidifying a future for the Great Barrier Reef

In the midst of challenges the Great Barrier Reef continues to face, there is a glimmer of hope. Continued advances within the scientific community and innovative methods to manage the reef are paving the way to ensure the future success of the reef. The reef itself, withstanding unprecedented bleaching events and showing continued recovery offers a true and unparalleled testament to its ability to recuperate.

As we strive to reverse the impact climate change has had on the world, inspiration can be found in the resilience shown by the Great Barrier Reef. It is an absolute symbol of hope that, with continued commitment and collaboration within the worldwide community, the reef can continue to thrive as a sanctuary for an abundance of marine life and be a source of absolute wonder for many generations to come.


IX | Commentary

Creating this storymap overall proved to be quite an engaging undertaking, offering the freedom to explore a topic of our choice whilst maintaining academic integrity. The ArcGIS platform was reliably flexible in terms of being able to create an aesthetic and an overall visually appealing presentation. This report incorporated an appropriate colour scheme that reflected the theme of corals and bleaching - blues and whites. The palette blended seamlessly with the imagery used, utilizing the design option to customize the 'separator' tool to depict a white coral, a poignant symbol to the story of coral reefs and bleaching.

What went well / What could be improved

While the reports main focus on the Great Barrier Reef provided a well-balanced and concentrated study, it became apparent that a broader study of global coral reefs could have enriched the narrative considerably. For instance, using a mass bleaching event from a different location on earth and comparing both. Most notably the recent mass bleaching within the kelp forests off the coast of Los Angeles (2017), which attracted an abundance of attention due to the unprecedented severity. In a recent study ' Biological annihilation via the ongoing sixth mass extinction signaled by vertebrate population losses and declines ', as a result of warming ocean temperatures, nearly 90% of corals within the kept forest showed clear signs of stress. Here, I could have made the comparison with Terry Hughes' ‘Global warming impairs stock-recruitment dynamics on corals’, which found similar statistics on the Great Barrier Reef (see section III).

Whilst the use of non-Wiki Commons images required careful consideration when attributing them to ensure the original creators were recognized, the majority of images adhered to this. However, some may have inadvertently lacked the right attribution due to the nature of obtaining the image.

Adding additional maps and detailed elements to existing maps could have further enhanced the storymap's overall impact. Additions could have included a visual distribution of reef sections with accompanying landmarks such as rivers, streams and human population centers. This would have provided more context to the geography of the area and corresponded with physical factors that were affecting the reef. Furthermore, a global map showcasing coral reef distribution, loss, and bleaching trends would have been the keystone in providing cross-country comparisons and creating further linkages to cultural and tourism aspects. Therefore, in a hypothetical reproduction of the assignment, I would have delved into human aspects that influenced the reefs beyond climate change., e.g., tourism as an example that causes stress and subsequent bleaching.

Conclusion

Overall, the storymap was insightful and had a good structure, however additional refinements could've elevated the overall impact as many of the issues felt very localized to one specific area and didn't give the 'global emergency' impact I had originally anticipated. Comparing the Great Barrier Reef to other reefs, such as those in California, would have provided a greater breadth of insights to their unique challenges and conservation strategies. Additionally, a greater examination on anthropogenic impacts on coral reefs would have provided a more holistic understanding of the multifaceted threats that global coral reefs face.


X | Citations:

ABC News. (2022) Dramatic improvement in coral cover seen in parts of Great Barrier Reef, ABC News. Available at: https://www.abc.net.au/news/2022-08-04/great-barrier-reef-report-says-coral-recovering-after-bleaching/101296186 (Accessed: 14 December 2023). 

Australian Government. and Queensland Government. (2021) The reef 2050 plan, DCCEEW. Available at: https://www.dcceew.gov.au/parks-heritage/great-barrier-reef/protecting/reef-2050-plan (Accessed: 14 December 2023). 

Australian Institute of Marine Science. (no date) Coral bleaching events, AIMS.gov. Available at: https://www.aims.gov.au/research-topics/environmental-issues/coral-bleaching/coral-bleaching-events#:~:text=2017,-Great%20Barrier%20Reef&text=Severe%20coral%20bleaching%20affected%20the,of%20the%20Great%20Barrier%20Reef. (Accessed: 14 December 2023). 

Australian Institute of Marine Science. (2023) Annual Summary Report of Coral Reef Condition 2021/22, AIMS. Available at: https://www.aims.gov.au/monitoring-great-barrier-reef/gbr-condition-summary-2021-22 (Accessed: 14 December 2023). 

Berkelmans, R. and De’ath, G. (2015) GBR - coral mass bleaching extent in 1998 and 2002 by Aerial Surveys (MTSRF 1.1.5, aims), eAtlas. Available at: https://eatlas.org.au/data/uuid/2a17791d-8175-481b-8d31-c25f02e66ef6 (Accessed: 14 December 2023). 

Britannica, The Editors of Encyclopaedia (2023) Great Barrier Reef, Encyclopaedia Britannica. Available at: https://www.britannica.com/place/Great-Barrier-Reef (Accessed: 14 December 2023). 

Cantin, N., Klein-Salas, E. and Frade, P. (2021) Spatial variability in bleaching severity on the Great Barrier Reef during 2016 & 2017 (NESP TWQ 5.7, NESP TWQ 4.2 and NESP TWQ 3.3.1, aims), eAtlas. Available at: https://eatlas.org.au/data/uuid/2805dd6c-1391-4df4-8137-e2a97f35a254 (Accessed: 14 December 2023). 

Ceballos, G., Ehrlich, P.R. and Dirzo, R. (2017) Biological annihilation via the ongoing sixth mass extinction signaled by vertebrate population losses and declines, 114(30). doi:10.1073/pnas.1704949114. 

Great Barrier Reef Foundation. (no date a) Growing heat tolerant corals, Great Barrier Reef Foundation. Available at: https://www.barrierreef.org/what-we-do/projects/growing-heat-tolerant-corals (Accessed: 14 December 2023). 

Great Barrier Reef Foundation. (no date b) Reef restoration, Great Barrier Reef Foundation. Available at: https://www.barrierreef.org/what-we-do/projects/reef-restoration (Accessed: 14 December 2023). 

Great Barrier Reef Foundation. (no date c) Water quality, Great Barrier Reef Foundation. Available at: https://www.barrierreef.org/what-we-do/reef-trust-partnership/water-quality-improvement (Accessed: 14 December 2023). 

Great Barrier Reef Marine Park Authority. (no date) Animals, gbrmpa. Available at: https://www2.gbrmpa.gov.au/learn/animals (Accessed: 14 December 2023). 

Great Barrier Reef Marine Park Authority. (2022) Strategies to manage the reef, gbrmpa. Available at: https://www2.gbrmpa.gov.au/our-work/reef-management-strategies/strategies-manage-reef (Accessed: 14 December 2023). 

Hughes, T.P. et al. (2019) ‘Global warming impairs stock–recruitment dynamics of corals’, Nature, 568(7752), pp. 387–390. doi:10.1038/s41586-019-1081-y. 

Sobtzick, S. and Marsh, H. (2015) The IUCN Red List of Threatened Species, IUCN Red List of Threatened Species. Available at: https://www.iucnredlist.org/species/6909/160756767 (Accessed: 14 December 2023). 

Taylor-Brown, K. (2023) Mass coral breeding methods amidst raft of breakthroughs to protect reefs - science meets business, Science Meets Business - Connecting science with industry. Available at: https://sciencemeetsbusiness.com.au/mass-coral-breeding-methods-amidst-raft-of-breakthroughs-to-protect-reefs/ (Accessed: 14 December 2023). 

United States Environmental Protection Agency (2023) Basic information about coral reefs | US EPA, Basic Information about Coral Reefs. Available at: https://www.epa.gov/coral-reefs/basic-information-about-coral-reefs (Accessed: 14 December 2023). 

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