Why is Coral Bleaching?

Gab Gab August 22nd, 2017

In my last post, I talked about the fact that coral around the world is bleaching. Today, I want to talk about why this is happening.

First I need to explain something from Geology.

It’s called the Milankovitch Warming Cycle, and it has been used as a dog whistle in oil company propaganda, as evidence that the current global climate change is “natural.”

Let’s look at the cycle in terms of atmospheric CO2.


So, what exactly is the Milankovitch Warming Cycle?

Well, it describes the natural oscillation of the global climate since the formation of Earth. The global environment has varied in temperature in a natural cycle over hundreds of millions of years.

The key thing to know is that it happens very slowly.

When I say very slowly, you are probably thinking in human terms. I don’t mean in humans terms. I mean; it moves incredibly slowly in geologic time.

According to the natural cycle of our planet, it should take thousands of years for the temperature to change a fraction of a degree.


So why does it matter how fast the Earth warms up? Won’t it just cool down as part of a natural cycle and then all the plants and animals will go back to normal?

In a word, no.

To understand why, we have to talk about how organisms evolve. You see, evolution happens when a gene mutates and causes a new trait to appear in a species. If that trait is beneficial, it will help the offspring who have it to outperform their counterparts without it. This helps that trait survive.

It’s easiest to see when we look at specific examples, so let’s have a look at polar bears. There were not always polar bears. But that species came into existence when, during an ice age, a bears’ genes mutated and caused the offspring to be white. The white bear did better than the others because it could hide in the snow, and so it was able to pass on its genes year after year.

Over time, that single genetic mutation became a new species. But again, the key to all of this is that it happens slowly over time.

Now that we understand how slowly the climate is supposed to change and how evolution works, you should be able to see how those two processes have worked together in tandem since the Earth was formed.

In the past, the climate changed slowly, and animals and plants adapted slowly.

Unfortunately, the climate is changing too fast now for any life forms to evolve with it. So when the zooxanthellae inside the coral die, and then the polyps die, that is it for coral.

Some species are hardier than other and so they will die in future bleaching events. However, we do know that all of them will die. The temperature is simply heating up too fast.

Gab Gab August 22nd, 2017

The mass extinction event that we are witnessing is part of The Holocene Extinction.

The oil companies try to tell you is that the Holocene extinction is perfectly natural and couldn’t be helped. This is 100% untrue. Man-made climate change is currently happening because of our use of fossil fuels, and the death of the coral reefs worldwide is absolutely our fault. The body of evidence is overwhelming. Science has no doubt on the matter.

And so, the answer to the question of “Why is the coral dying?” is really very simple.

The answer is us.

Gab Gab August 22nd, 2017

How Coral Bleaches

Healthy Coral

Above you can see a picture of healthy coral that has not been bleached. This picture was taken at Gab Gab Beach on Big Navy Base Guam, on April 21st, 2017.

Now then, last time I posted I talked about how coral is a living organism comprised of smaller organisms. These smaller organisms are called Polyps, and they are tiny animals. This is why you should never touch or stand on coral, because it crushes the tiny animals that it is made of.

This time, I want to talk about how coral bleaches.

First, remember that a coral is like an apartment complex. The building is made of calcium secreted by the coral, and the people who live inside are called polyps.

This is what a polyp looks like.


As we discussed last time, a coral polyp can eat food from the water that it catches with its tentacles.

However, it is like a Venus Fly Trap: Even though a Venus Fly Trap eats flies, it still needs to absorb sunlight so that it’s chloroplasts can metabolize that light into food for the plant. Without sunlight, it would die.

The specialized chloroplast cells inside of a coral polyp are called zooxanthellae. Even though the coral is perfectly capable of catching food from the water with its tentacles, each polyp still needs its zooxanthellae to metabolize sunlight and produce a reliable food source for the polyp.


The zooxanthellae are actually all different colors, and they are what gives coral its color. The polyps themselves are clear.

The problem is that the zooxanthellae are sensitive to temperature. If it gets too hot, the zooxanthellae will die. When they die, the polyp expels them into the water, and thus, it loses its color.

This is why coral that is bleached is not yet considered “dead.” The polyp is still alive, but it has lost its zooxanthellae.

coral bleaching chart.jpg

Rare cases have been reported where a coral bleached, but then the polyps were able to catch new algae cells and survive. However, the unfortunate truth is that once a coral bleaches, the polyps are very likely to starve to death and die.

Once the polyps die, the calcium skeleton is all that is left. This skeleton then becomes host to parasitic lifeforms that eventually break it down.

I moved to Guam is August of 2015. In the time that I have been here, I have seen the coral in Tumon Bay bleach and die, as well as the coral inside the reef at Tanguissen Beach.

Gab Gab August 22nd, 2017

However, those are shallow reefs. I understand how they got too hot and their coral began to bleach.

On the other hand, Gab Gab Reef on the Big Navy Base is much deeper. Most of the coral sits at around 20 feet deep, depending on the tide.

And rather than being in an enclosed reef the way the coral in Tumon Bay and Tanguissen is, the coral at Gab Gab is in a very deep harbor.

Gab Gab August 22nd, 2017

I never imagined that the coral at Gab Gab would bleach.

At least, not before I left here in September of 2018. And yet, the images that you are seeing now are from Gab Gab, and they were taken just a few months after the picture of healthy coral at the top of this post.

This is what bleached coral looks like. This is what a reef looks like when it is dying.

Gab Gab August 22nd, 2017

The reef at Gab Gab was truly amazing. It was filled with an incredible diversity of life, and a wide variety of corals. And now, before my eyes, it is dying.

I can’t really tell you the emotional toll of watching corals die.

I know that these are structures that took generations of polyps to build. Many are hundreds of years old. Gab Gab has so many huge, ancient corals that are each home to hundreds of fish.

Gab Gab August 22nd, 2017

It is an environment that took nature so many lifetimes to create. And yet, it is dying in the span of one Navy Man’s tour of duty on Guam. (My husband Rich.)

By the time the military sends my husband to a new port, I will have witnessed the loss of a huge percentage of the coral reefs on Guam. Just four years… and yet, I am seeing so much death.

There is no eulogy solemn enough or beautiful enough to pay tribute to the coral reefs of Guam. They were some of the most amazing things that I have ever seen, and I wish that I could express to you what a huge loss this is to every single one of us.

I am actually having trouble typing this because of the tears. And, if you were watching our oceans dry each day in real time, I have no doubt that you would feel the same.

There is no data yet on how big the 2017 world bleaching event will be. However, I would like to submit these photos to the world and to NOAA as evidence of the death in my small corner of the ocean.

Coral is Alive


I don’t usually use this blog to educate people about science, but I am afraid that I feel it is necessary. So let’s take a moment to learn about coral, and what it is made out of.

Coral comprised of thousands of tiny animals called polyps.

Polyps are too small to see with the naked eye, but under a microscope you can see that a piece of coral is not a single entity. Rather; it is like an apartment complex.

A cooperative colony of polyps that all live together comprises what we think of as “a coral.”

images (1)

Inside the coral polyps are something called zooxanthellae.

Zooxanthellae are specialized chloroplasts that are able to take sunlight and metabolize it into food for the coral, the same way a chloroplast in vegetation absorbs sunlight and metabolizes it into food for its its plant host.


Some corals also have tentacles that they stick out in order to try to catch bits of food that go by. However, all coral are dependent on their zooxanthellae for long-term survival.

You can think of a carnivorous plant like a Venus fly trap: it eats flies, but it will still die without the nutrients its chloroplasts make from sunlight.

This is why you must never touch coral. When you touch it or step on it, you are smashing hundreds of tiny polyps, and this does permanent damage to a coral. In fact, certain kinds of sunscreen are poisonous to coral, so you may even kill the entire colony just by being clumsy.

The lesson? Coral is a living organism made of many smaller living organism, and it’s not okay to touch it.


Public Service Announcement

Not cool


I am getting sort of frustrated with a few things I see on the island, and I wanted to talk about them. First and foremost, I want to say that I am horrified when people don’t stay two meters away from endangered animals, as is required by federal law.

Fish Eye is a problem. I know it. You know it. Everyone on Guam knows it. They feed the marine life by dumping chum in the water, and it can cause all kinds of bad situations like the semi-domestic barracuda that lives there and has injured people, or the turtle that learned the dangerous and unfortunate lesson that people equal food, and paid for that lesson with his life.

While we can all look around and see that other people are doing things wrong, let us please also remember that others’ mistakes do not give us the right now also break laws and behave badly. Do not touch or get within two meters of endangered animals. This includes the native birds, coconut crabs, sea turtles, and anything else you might encounter that is rare and in need of protection.

Please, don’t pet or feed the animals.


so not cool


Next up: the coral is alive. Coral is a living colony of organism called polyps. and they get crushed when you stand on them.

I see people all the time at Gun Beach, Fish Eye, Gab Gab, and Tanguisson just standing on the coral like it’s not big deal. And FYI: it’s not better if you are barefoot. I don’t care what you stand on a polyp with. It is a tiny animal and you will kill it by standing on it.

Some coral can appear to be dead, but still have living sections on new corals trying to grow on top of the old. Just because it doesn’t look alive to you, doesn’t mean that it is not alive. So don’t stand on anything at all unless it is sand. If you can’t float well enough to adjust your mask or whatever in the water, then get out of the water to do it if you can’t find sand. Just don’t stand on the coral.


dont do it


And finally: Every time I go out I find trash. Every single time. Last time I went out I was at Gab Gab and I found a Planters Peanut bag. In Tumon Bay and at Tanguisson I usually find beer cans and flip flops. At Fish Eye I found umbrellas, sun glasses, hats, and all kinds of other garbage.

The point is this: The ocean is not your landfill. Stop dumping your trash in the ocean like it doesn’t matter. It matters a lot.



I guess what I really want you to do it be responsible and kind. Oh, and recently someone stole my flip flops off the rocks by the ocean while I was swimming. So although it should go without saying: Don’t steal people’s things while they are in the water!

Just be cool, folks. Be cool.


One of the workers at Fish Eye feeding Squid to the turtle that used to live there. Don’t ever do that!


An umbrella that we found wedged in some coral at Fish Eye. We took this picture with it before bringing it to shore to throw away.