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Coral Reefs Are In Hot Water


American Samoa, Before: December 2014. After: February 2015. Image: XL Catlin Seaview Survey

By now you have probably heard the news that coral reefs all over the world are currently in danger of bleaching. A perfect storm of already increasing sea surface temperatures paired with one of the largest El Nino events in recorded history have left many coral reefs in literal hot water. In March 2015, NOAA announced the arrival of the what would turn out to be one of the largest El Nino events in history, and warned of the consequences to coral reef ecosystems around the globe. As the year went on the El Nino event has continued to get stronger and stronger and is now predicted to last well into 2016. What this means for coral reefs could be devastating.

Coral Bleaching Infographic Image: NOAA

Coral Bleaching Infographic
Image: NOAA

First, let’s dig deeper into what coral bleaching is. Corals are animals that create colonies out of thousands of identical, yet individual, coral polyps. In order to create these colonies the polyps produce a calcium carbonate skeleton. Producing such an elaborate skeleton requires a large amount of energy, much more energy than the coral is able to produce. This is where zooxanthellae comes into play. Zooxanthellae is a small plant-like dinoflagellate. The zooxanthellae actually inhabits the tissues of coral in perhaps the natural worlds best example of symbiosis. This is also responsible for giving the corals the spectacular range of colors so notorious on coral reefs. The catch, is that both the coral and its symbiotic zooxanthellae are very sensitive temperature change. As the surrounding water temperatures increase these little dinoflagellates get stressed out and begin producing reactive oxygen species (ROS). These ROS actually harm the coral and can even lead to programmed cell death (PCD). In order to protect themselves, corals begin to expel the zooxanthellae in a last second effort to save themselves. This expulsion of zooxanthellae is what we refer to as coral reef bleaching. As the zooxanthellae leaves so does the color, leaving only the transparent tissue and a bleach-white skeleton underneath. Though bleaching is not a good thing and is commonly affiliated with environmental disaster, it is actually the corals way of survival during thermal stress. That’s not to say that all is okay during a bleaching event. The coral will die if the temperature does not decrease within a couple weeks.

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We are currently seeing significant bleaching in the Hawaiian Islands, which I personally witnessed in Kāneʻohe Bay on Oahu and in the Kapoho tide pools on the Big Island in late August. The corals in the Caribbean are also suffering. Bleaching in Southern Florida and the Keys have already been documented and the outlook for reefs south of Florida are only getting worse. Reefs in Haiti, The British Virgin Islands, The Dominican Republic and the Lesser Antilles are likely to have bleaching events in the coming months. In fact, this morning I was tipped off by a viewer asking if the corals at T4O’s Grand Cayman research site were bleaching. I immediately checked our live underwater camera and was shocked to see the large coral heads of Montastrea annularis beginning to bleach. Now this is obviously bad news, but even worse, this is just the beginning. Summer has just ended in the northern hemisphere. And although El Nino will continue in theCaribbean and Hawaiian islands for the next month or so, the southern hemisphere is heading to summer  and reefs throughout the Southern Pacific and Indian Oceans could be facing a catastrophic bleaching event. The current consensus is The Great Barrier Reef will get hit hard with coral reef bleaching in 2016. And although the great Barrier Reef is the most well known reef on the planet, it is far from the only ecosystem in the region. The Great Barrier Reef is part of the coral triangle, a region spanning Australia, Indonesia, Philippines, and Malaysia. This entire region, which supports hundreds of coral species, is projected to be hit with extremely warm water. And that doesn’t even include most of the Indian Ocean which will also get hit with high SSTs. There is a very real possibility that we are witnessing the 3rd Global Bleaching Event on record, (1998 & 2010 previously).


Coral Bleaching Model for October 2015 – January 2016. Image: NOAA


Coral Bleaching Model for February 2016 – May 2016. Image: NOAA


So why does this matter? Coral reefs are like forests, they need time to grow back and become healthy. Since the 1980’s bleaching events have become more and more frequent. Global coral coverage is said to have decreased nearly 30% in just a few decades and the current pace of change is quite simply to fast for the corals to keep up. Coral bleaching can not only cause mortality, but also has a continued effect on those that do survive. Corals that do make through the hot times tend to become more prone to disease and other stressors. We are talking about about an ecosystem estimated to be worth around 30 billion dollars per year and supporting over 500 million people who depend on it. That’s 30 billion dollars that live in less than 1% of our ocean and that number continues to decrease. 25% of all marine life makes the coral reef home at some point in their lives and without the reef, life in our oceans would become much different. Scientists all over the world have warned that within 40-50 years coral reef ecosystems may not even exist, a drastic prediction that actually could be correct. In the end corals provide:

  • Habitat: Home to over 1 million diverse aquatic species, including thousands of fish species
  • Income: Billions of dollars and millions of jobs in over 100 countries around the world
  • Food: For people living near coral reefs, especially on small islands
  • Protection: A natural barrier protecting coastal cities, communities and beaches
  • Medicine: The potential for treatments for many of the world’s most prevalent and dangerous illnesses and diseases.

Are we really willing to sit back and watch one of the most essential ecosystems on this planet dwindle away? El Nino or not, it is about time we did something to protect our natural world that provides us with life. When it comes down to it, it may be those divers, surfers, and scientists who point it out and raise a fuss, but they are not ‘tree huggers’ and environmentalists. They are just like the rest of us, but they’ve watched our coral reefs change over the years and they’ve seen their demise first hand. Just because you do not have a personal connection with our oceans does not mean it does not affect you. We are all inextricably tied to the sea and it is our responsibility, as a species, to protect the ecosystems that have enabled us to thrive.


My name is Zack Rago. I am the Research & Outreach Coordinator here at Teens4Oceans. I came to Teens4Oceans because I have a deep passion and love for our oceans as a whole and in particular the corals that make up our stunning coral reef ecosystems around the world. I fell in love with coral reefs at a young age and they have been the driving force that ultimately landed me with T4O. Corals are truly incredible organisms. Aesthetically there is nothing else on the planet as beautiful, the colors, the structures, the vast wealth of life they support, and the minute details that take every ounce of attention to see. Corals are some of the simplest, yet most complicated organisms on the planet. Stationary, yet incredibly architectural. Primitive, yet amazingly efficient. Smaller than a pin or bigger than your house. Unbelievably resilient, yet dramatically fragile. However, in today’s world corals are facing massive changes and are the most threatened ecosystem on the planet. This is a fact that has bothered me for quite some time and I’ve wanted nothing more than to protect what I love from what could be their extinction. 

In 2014 our planet began shifting into what would eventually become the largest El Nino event on modern record. Immediately, the coral reef community was on high alert for a mass coral bleaching event. As luck would have it, I met an amazing team who was working on a project traveling the globe with the goal of documenting the degradation of coral reefs and particularly this phenomenon of coral bleaching. I was given the opportunity to join their project and assist in documenting the dismal situation that our coral reefs are facing.
Historically, coral bleaching events on large scales are affiliated with very strong El Nino events. In 1997-98 we recorded the largest El Nino to date and on top of that we witnessed the first Global Bleaching Events ever recorded. When we say Mass Global Bleaching we mean exactly what we say. In the last year and a half we have seen large scale bleaching on coral reefs world wide. From Hawaii, the Caribbean, Fiji, Kiribati, New Caledonia, American Samoa, Indonesia, and finally onto the crown jewel, The Great Barrier Reef, this has been quite literally a global event. Many of these reefs have even been hit twice in that time frame and the event isn’t even finished. In the next few weeks we anticipate seeing further bleaching in the Indonesia region, the East Coast of the Africa, and the Maldives. 

So what happens to corals when the water gets hot. Corals are a very simple yet very complicated organism. In fact, they are essentially two organisms that make up one, the holobiont. Corals have zooxanthellae, a little tiny algae (Dinoflagellates called Symbiodinium) that are incorporated into their tissues. These symbionts, as we like to call them, produce the energy the coral needs to survive, flourish, grow and also give the corals the spectacular array of colors that we adore so much. They produce this energy with the magical power of photosynthesis. Simply put, corals incorporate zooxanthellae into their tissue in order to use the power of photosynthesis without actually being photosynthetic themselves, an amazingly beautiful evolutionary feat. Here’s the catch. When the water gets to hot these symbionts begin to produce nasty molecules called reactive oxygen species (ROS) that will kill coral. In a last ditch effort to save themselves corals begin to expel this algae from there tissues before it’s to late. This expulsion of symbionts is a process termed bleaching. As the symbionts are expelled the stunning colors of the coral disappear with it, leaving behind the bright white skeleton of the coral covered in a thin transparent tissue. Given that water temperatures return to normal some coral can recover and become once again colorful and beautiful. But, without their little energy producing algae these corals can only last around a month. If the temperature stays to warm any longer than that most corals will die and be taken over by muck and algae. 

Now that we have that sorted out, back to El Nino. We are currently facing the largest Global Bleaching event ever recorded. Right this moment over 95% of coral reefs in the northern portions of the GBR are severely bleached. I am currently based on Lizard Island where the bleaching has been at an extraordinarily level never seen before. I dive twice a day every single day in order to watch these corals. The amount of death that I have witnessed in the past week is on a scale that I can hardly articulate into words. I estimate that nearly 100% of the hard corals are bleached with most being severe. Currently I estimate that mortality among these hard corals is around 25-30% and that number climbs every day. If was telling this story 48 hours ago that number would have been 15%… I’ve been in Australia for nearly 4 months now documenting corals. I have watched an ecosystem I dreamt about for my entire life die in front of my eyes, literally. This place is one of the wonders of the world, the largest living organism on the planet and arguably the most ecologically diverse system in nature. Coral reefs provide sheltered coasted for millions of humans around the globe, provide a substantial amount to the global economy, and most of all keep the balance of the worlds oceans, and in turn the planet as a whole, making earth suitable for life as we know it. 

I know it is hard to identify with catastrophe unless it effects you directly, and I know that not everybody has the opportunity to see the reefs the way I have been able to. But if you could see what is happening underwater you might be able to grasp and understand the enormity of this disaster. Over the last 4 months I have taken hundreds of photographs on these reefs. I have chosen over 40 of these images to share with the world in the hopes of exposing the reality of what we are doing to our oceans. While I gave my best attempt to keep them captivating I hope that you can also recognize the grim and haunting reality that they represent. 

We can do better. We must do better.​​​​​