Coral Reef Bleaching—Why the Great Barrier Reef is in Trouble


Why are the corals on the Great Barrier Reef off of Australia bleaching? Why is coral bleaching important? First a little background on corals.

Hi, I’m Polly, a coral polyp. The animal you think of as “coral” is actually made up of lots of little coral polyps. We use calcium carbonate to make our skeleton and many of us together make the base of a coral reef.

We’re only millimeters wide (0.1 inch) and centimeters deep (1.2 inches) with tentacles sticking out. We use our tentacles to find food floating in the water.

But our main source of food is made for us by our friends inside us, the zooanthellae. These are our photosynthetic symbionts. In other words, the plants inside of us use sunlight to make the food that we eat. These zooanthellae are important to us, but when exposed to stressors like increased heat or acidity, they often expel themselves from us. This causes coral bleaching.

Coral bleaching can be caused by the ocean warming due to climate change. The ocean absorbs 90 percent of the heat in the atmosphere caused by human activities. Coral bleaching can also be affected by ocean acidification. The ocean becomes more acidic (like soda or stomach acid) when it absorbs carbon dioxide from the atmosphere. There is also pollution of all sorts, including plastic, chemical, and sediments that can also cause the coral reef to bleach.

A recent scientific study found that “huge portions” of the northern end of the Great Barrier Reef died last year due to warming seawater. Just an increase of two or three degrees Fahrenheit (1.2-1.6 degrees Celsius) can cause bleaching. The southern end of the Great Barrier Reef is bleaching as we speak.

So why do we need coral reefs? Coral reefs house twenty-five percent of all marine life in the oceans.
One billion people rely on the ocean for their primary source of protein
, and many of those in developing countries rely upon coral reefs for it.

So what can you do? Here are some excerpts from the Nature Conservancy’s 10 Easy Steps to Protect Coral Reefs

1. Support businesses such as fishing, boating, hotel, aquarium, dive or snorkeling operators that protect coral reefs.
2. Practice safe snorkeling and diving practices such as not touching the coral and not anchoring on coral.
3. Volunteer on vacation to clean-up a coral reef or help plant one.
4. Plant a tree to reduce the carbon dioxide in the atmosphere.
5. Dispose of your trash (or recycle!) properly, especially near the ocean. Better yet, join a beach clean-up.

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