Category Archives: Great Barrier Reef

Coral Bleaching of the Great Barrier Reef

The following article first appeared on the Research Blog for Dr. Neil Hammerschlag’s Shark Research and Conservation (SRC) Lab website at the University of Miami’s Rosenstiel School of Marine and Atmospheric Science. To learn more about SRC, visit here:, or to learn more about the University’s marine science school, please click here:

By Delaney Reynolds, SRC intern

Coral reefs are some of planet earth’s most spectacular, diverse and important ecosystems. Our planet’s coral reefs provide important shelter, habitats, and a source of food for many different species of marine organisms. They also act as a critical food source to humans, as well a natural barrier to help protect our coastlines from hurricanes and associated storm surges. Sadly, coral reefs face growing risks including the possibility of extinction from a variety of stresses that leads to coral bleaching.

Coral Bleaching

Figure 1: Coral from which the zooxanthellae has been expelled, causing it to turn white (Image Source:

Coral bleaching is the process in which zooxanthellae, algae living symbiotically within the coral, are expelled from coral colonies due to a number of factors including an increase in temperature, decrease in pH, exposure to UV radiation, reduced salinity, and bacterial infections. Zooxanthellae provide the coral 30% of its nitrogen and 91% of its carbon needs to the coral host in exchange for a shelter, as well as waste produced by the coral from nitrogen, phosphorus, and carbon dioxide that is required for the algae’s growth (Baird, 2002).

When corals bleach, it effects entire marine communities due to their immense diversity. Fish populations that reside around coral reefs “are the most species dense vertebrate communities on earth, contributing critical ecosystem functions and providing crucial ecosystem services to human societies in tropical countries” (Graham, 2008). Researchers have found that when an ecosystem endures physical coral loss, fish species richness is extremely likely to decline due to their heavy reliance on the coral colony itself (Graham, 2008).

Perhaps the most famous current example of coral bleaching is Australia’s Great Barrier Reef. Scientists have determined that the main cause of Great Barrier Reef coral bleaching is induced thermal stress and that about 90% of the reef has been bleached since 1998 (Baird, 2002). As the corals bleach and temperatures increase, researchers have determined that shark and ray species that live in the area may be vulnerable to these climactic changes.

Exposure of Ecological Groups of GBR Sharks and Rays to Climate Change Factors

Figure 2: Exposure of Ecological Groups of GBR Sharks and Rays to Climate Change Factors. This figure displays the vulnerability different elasmobranch species face due to climate change, as well as the specific effects of climate change that they are vulnerable to, in the specific zones of the Great Barrier Reef. (Image Source: Chin et al. 2010)

Most of the Great Barrier Reef is located on the mid-shelf of the ocean floor, the approximate mid-point between the shallower coast of Australia and the continental shelf where the ocean bottom significantly drops in depth. Researchers found that the mid-shelf is the area where most of the shark species studied reside, while most rays dwell in coastal waters or closer to the continental shelf. It was also found that both areas are the susceptible to rising temperature, increased storm frequency and intensity, increasing acidity, current alterations, and freshwater runoff, all being caused by climate change (Chin, 2010). Based on these findings, researchers have concluded that the areas these elasmobranchs live in should be protected and preserved. Species in these highly vulnerable areas should also be monitored and considered for future conservation actions, as many of the shark species are already experiencing the effects of climate change from some of the aforementioned factors.

Typically, sharks are considered some of the strongest animals on earth, and while they have lived on earth for at least 420 million years, they are slow to adapt. This slowness has impeded their ability to survive in our rapidly changing climate. In the near future it will be common to see some species of marine organisms demonstrate plasticity, the ability to adapt to their changing environment, but other species, such as elasmobranchs, are expected to simply distribute to other habitats in search of cooler waters. Even though sharks are a highly vulnerable species to climate change, they sit at the top of the trophic level in many different niches and, thus, wherever they migrate to, it will be easier for them to find food than it would be for other species such as fish or rays. However, this is most likely only the case for adult sharks as embryos and juvenile sharks may be more vulnerable to increased temperatures. For instance, researchers found that the survival of bamboo shark embryos decreased from 100% at current temperatures to 80% under future ocean temperature scenarios and that the embryonic period was also shortened, not allowing the embryo enough time to develop fully (Rosa, 2014).

To decrease the effects of climate change on coral bleaching, corrective and mitigation measures can be taken. By utilizing green energy sources such as implementing solar power or wind power, walking or biking, and driving electric cars, we can reduce our use of fossil fuels and carbon footprint, thus decreasing the amount of carbon dioxide polluting and warming our atmosphere and oceans. While underwater and not always visible, coral reefs are truly a vital part of our ecosystem and need to be cherished and protected for generations to come.


Baird, A. H., & Marshall, P. A. (2002, July 18). Mortality, growth and reproduction in scleractinian corals following bleaching on the Great Barrier Reef. Retrieved from

Chin, A., Kyne, P. M., Walker, T. I. and McAuley, R. B. (2010), An integrated risk assessment for climate change: analyzing the vulnerability of sharks and rays on Australia’s Great Barrier Reef. Global Change Biology, 16: 1936–1953. doi:10.1111/j.1365-2486.2009.02128.x

Graham, N. A., McClanahan, T. R., MacNeil, M. A., Wilson, S. K., Polunin, N. V., Jennings, S., . . . Sheppard, C. R. (2008, August 27). Climate Warming, Marine Protected Areas and the Ocean-Scale Integrity of Coral Reef Ecosystems. Retrieved from

Rosa, R., Baptista, M., Lopes, V. M., Pegado, M. R., Paula, J. R., Trubenbach, K., . . . Repolho, T. (2014, August 13). Early-life exposure to climate change impairs tropical shark survival. Retrieved November 2, 2017, from

The United Nations


Solving our planet’s climate crisis requires that societies all over earth must evolve from a fossil fuel energy economy to a sustainable one during my lifetime. And for many of the most fragile places on earth and their inhabitants, those most susceptible to rising seas and other risks, the stakes are the difference between survival and extinction.

Every citizen of our planet now faces a crisis that has no boarders, one where people’s language, religion or the color of their skin simply, and thankfully, do not matter. For this reason my recent opportunity to address the General Assembly of the United Nations in New York City was a unique and important chance to draw global attention to the fact that we need all of today’s world leaders to begin embracing change. The type of positive change that our world needs to solve our environmental problems before it’s too late.


At UNESCO’s invitation, children from all over the world representing their World Heritage Marine sites including some of earth’s most iconic, yet endangered environments, such as Australia’s Great Barrier Reef, Ecuador’s Galapagos Islands and South Florida’s very own Everglades National Park, gathered to ask UN members to join us in pledging their support. The diversity of the children was profoundly beautiful but even more impressive was the passion that these children have for our planet.

#MyOceanPledge Ceremony in NYC.

To be asked to speak on their behalf, both for the children that joined me on stage at the UN in New York and children all around the world was the greatest honor of my young life. My speech to the General Assembly sought to define why these special places are so important but to also illustrate that they are at dire risk. As I shared with the audience that day;

“in our increasingly virtual world, nothing can compare to the majestic beauty of our natural environment, those special places on our planet that touch our hearts and that inspire our imagination.

Such places have had a profoundly important impact on our society for generations but they are also fragile and face many challenges, in some cases even extinction, from risks including coral bleaching, our planet’s climate change crisis, overfishing, pollution from plastics or run off from pesticides to name just a few.”

#MyOceanPledge Ceremony in NYC. #MyOceanPledge Ceremony in NYC.

And we called upon the world’s leaders to join us in taking the #MyOceanPledge by signing a petition that recognizes the environment’s importance to our collective futures. To read more about the petition and why having the world’s leaders join us is so important to all of our futures please click here for Andres Oppenheimer’s timely editorial in yesterday’s Miami Herald entitled World May Not Melt, Despite Trump’s Insane Decision on Climate Change.

Mr. Oppenheimer’s editorial brilliantly recounts a recent interview that he conducted with none other than the United Nations General Assembly President Peter Thomson including his thoughts on President Trump’s short-sighted decision to withdraw from the Paris Climate Agreement. President Thompson knows that the world is serious about solving our climate crisis and he especially knows this based on what he saw and heard from the children and me during the U.N. Ocean Conference. As Mr. Oppenheimer wrote and shared: He said he noticed that movement during the U.N. Ocean Conference held June 5-9, shortly after Trump’s decision. At that meeting, he said, there was a “hugely positive wave” of support for action against climate change, which included “a very big input from America’s civil society, states and cities.”

I noticed it too during my time in New York, at the UN and at the other events leading up to Worlds Ocean Day that we attended. It was everywhere and was what Mr. Oppenheimer quoted Mr. Thompson calling a “tidal wave of support” for action against climate change”.“I think what you’re seeing all the way from Europe to China and in the developing world, indeed everywhere I look, is that people are saying, ‘Hey, this only makes us stronger… I’m confident that people will step up on that. And I remind you that the biggest investors in renewable energy are American investors.”

#MyOceanPledge Ceremony in NYC.

And it was not just ‘talks’ and speeches but people taking action. Important people including heads of state, global business people and many others. People like Prince Albert II of Monaco, the first person to sign our pledge scroll and also someone Mr. Oppenheimer mentioned in his editorial when he wrote: Asked for specific examples of what is being done, Thomson cited the U.N. partnerships with celebrities such as billionaire Richard Branson and Prince Albert of Monaco to petition governments to protect 30 percent of their oceans by 2030. There is already an ongoing U.N. plan to have 10 percent of the oceans protected by 2020, and “I think that’s going to be doable,” he said.’

Delaney Reynolds preso

And speaking of Prince Albert II, here is a picture of my brother Owen and me, along with our friend Sarah Ramos, with the Prince of Monaco just after he signed the petition Mr. Oppenheimer wrote about, #MyOceanPledge. As you can see, he sure does not look too stressed about President Trump’s lack of vision or recent decision.During what was an incredible week in New York I had the privilege to get to know children from Papahanamokuakea, Hawaii; Lord Howe Island, Australia; Seychelles; South Africa; Sudan; the Great Barrier Reef, Australia; and the Wadden Sea, Netherlands among other World Heritage Marine sites. And no matter which amazing place these children live in we all shared the same undeniable bond; a deep love of the ocean and our natural environment.

IMG_3637And speaking of amazing places, the Everglades National Park is the only environment of its type on earth. The Everglades is a treasure chest filled with magical, mystical creatures unique to its enchanting and diverse environment, from its mangrove lined coasts and sandy beaches along our ocean’s shore to its majestic pineland forest and slow moving River of Grass. And it’s a big part of why I was invited to address the General Assembly.

While working on my book on sea level rise, Sink or Swim?, I had the pleasure of meeting and interviewing Everglades National Park Superintendent Ramos last year about the fragility and importance of this special place. Superintendent Ramos was generous with his time and shared a passion for the Park that left me feeling like the Park is in very good hands with a very good man.

Unfortunately, the Everglades is also at dire risk from all sorts of threats including encroaching development, agricultural pollution and run-off, rising seas and more. Sadly sea level rise alone threatens a large portion of the Park from possibly becoming extinct within my lifetime. As I said, it’s also one of UNESCO’s World Heritage Marine sites but its also a World Heritage in Danger site too given the many risks it faces to even have a future.

#MyOceanPledge Ceremony in NYC.

The folks at UNESCO in Paris saw a TEDx Talk I’d given a couple of years ago and, thus, invited me to address the General Assembly and have the honor of representing the Park and our region. And, if that was not enough, I was even able to be joined on stage by my brother, Owen, and our friend, Sarah.IMG_3684I have countless memories to share with you in future blogs about the outstanding children that joined me in New York, the time that we spent with people like Sylvia (‘Her Deepness’) Earle at The Explorers Club (only one of the coolest places you could ever hope to visit) and the truly exceptional people at UNESCO. I promise to share stories and pictures about all of those things and a lot more in time but, before I end this blog, allow me thank a few special people who were the reason I was honored to be asked to address the General Assembly.

#MyOceanPledge Ceremony in NYC.

Thanks to UNESCO, The Explorers Club, the Government of Flanders, Stefan and Irina Hearst, The Khaled bin Sultan Living Oceans Foundation, Dr. Fanny Douvere, Robbert Casier, Vanessa Lucot, Nolwazi Mjwara, Taylor Butz from the UNESCO World Heritage Center, Alison Barrat and Elizabeth Rauer from the Living Ocean Foundation, and Joel Sheakoski (for your amazing pictures).To each of you, thank you from the bottom of my heart for the work you do literally all over the world every day to protect some of the most important places on earth.

Thanks to Mom and Dad for facilitating the trip for Owen and me, much less introducing me to New York for the first time. I know that the entire experience was a bit overwhelming so thanks for not crying too much while we were on stage!IMG_3649Thanks to my #1, my not so little, little brother Owen. Thanks for standing outside the theaters with me to get autographs in the rain but mostly, thanks for standing on stage with me in front of the world and for always supporting my passions and dreams.IMG_3639And lastly, allow me to give a special shout out and thanks to the incomparable and ever so kind Pedro Ramos and his lovely daughter, Sarah. Pedro, it is my distinct honor to know you and to know that such a perfect steward of the environment is helping protect the Everglades. Its habitats, animals and I could never thank you enough.

OK, its time to get back to work on local solutions. Despite the circus that’s in Washington right now all of us have important work to do in our local communities, the regions and towns we live in, and in our states. If you’ve read this far then I would ask you to start local, stay local and find ways to make a positive change in your community. That’s my plan and I hope it’s yours too.

IMG_3689 #MyOceanPledge Ceremony in NYC. unnamed