Ocean Warming and Coral Reefs
August 1, 2012

this month's article is written by Caitlin Andrews for the MSPCA


healthy coral reef


bleached coral

photos from National Geographic

This summer has certainly been a hot one, but Jupiter has not let that stop her from having a good time. We’ve been seeking out the cooler times of day to go for walks, practicing agility on the shady side of our yard, and finding ways to keep her happy inside when it’s simply too hot to go out. There’s often a cool breeze by the ocean, so we try to make time to get to the beach—one of her favorite places—when we can. Even though Jupiter is not a water dog, she always makes a good effort. If I venture into the waves, she’ll dip her toes in, too, and—sometimes—she’ll even work up the courage to get in up to her belly. It’s another great way to cool off, but, unfortunately, Jupiter does not see it that way. In her mind, the ocean is one giant, chilly bathtub—which she doesn’t like in or out of the house.

Unlike Jupiter, I have been swimming in the ocean all my life, so I’ve built up a bit of immunity to the chilly waters off our coast. However, over the past several years, I’ve noticed a gradual trend of rising ocean temperatures—and it’s not just me. Ocean warming is a serious problem that is affecting ecosystems in our area and around the world, and it can be traced back to global climate change. When carbon dioxide traps heat in our atmosphere, the temperature of the air and the ocean increases. And, while, the increase in temperature might sound tiny (less than 0.2°F for the ocean), any change is a big change. On a planet that is approximately 70% covered by saltwater, a problem involving the ocean is a problem for all of us.

Let’s shift our attention to one ocean ecosystem in particular: the coral reef. We don’t have coral reefs in our area, but many of us have seen movies or aquarium exhibits about them, have read about them in books, or have even been lucky enough to travel to see one. Coral reefs are magnificent underwater ecosystems formed when colonies of animals called “corals” make hard, white skeletons out of a substance called calcium carbonate. These skeletons not only protect their tiny coral creators but also provide a habitat for an array of organisms—from fish that find shelter within the reefs’ nooks to starfish that attach themselves to the coral. The resulting communities are among some of the most diverse in the world and flourish in warm, shallow waters with lots of sunlight, especially tropical waters including those of the Caribbean.

Now, what do coral reefs have to do with me, Jupiter, and the warming ocean waters I’ve been noticing lately? That’s just it—they have everything to do with it. We just have to take one look at coral reefs to see the harmful effects that ocean warming—and, therefore, global climate change—have had on our planet. Corals depend on microscopic organisms called “zooxanthellae” that live in their tissues in a symbiotic relationship, or a partnership between two species that benefits both. Zooxanthellae are the source of corals’ reddish-brown color; as part of their close relationship, the corals give the zooxanthellae carbon dioxide, and the zooxanthellae provide the corals with oxygen. But ocean warming—even the small changes we have seen to date—spell disaster for corals and their zooxanthellae. Overall warmer temperatures stress the corals, causing them to release their zooxanthellae and, as a result, lose their color—leaving behind eerie white skeletons of bare calcium carbonate. Due to this fact, this process is often called “coral bleaching,” and most corals gradually die, as they suffer from disease, stunted growth, and decreased reproduction.

As if that weren’t enough, corals are also affected by “ocean acidification,” another result of the increased carbon dioxide in our atmosphere. When carbon dioxide reacts with water in the ocean, it decreases the pH of the water and ultimately makes much of the carbonate vital to corals unavailable. When carbonate is limited, corals cannot produce as much calcium carbonate, threatening their existence and the existence of the diverse communities that surround them. Sadly, coral communities are struggling to recover from the destruction caused by ocean warming and acidification, and marine biologists believe that this is just the beginning of coral reefs’ decline.

According to National Geographic, 30% of all coral reefs communities could disappear within the next 30 years due to human factors, including ocean warming and acidification. And, if nothing is done to help fix these problems, coral reefs will be just one of the many victims of ocean warming. There is much that we can and must do in order to halt future damage to our ocean and to preserve the incredible diversity that is found on our planet, and there is much that you can do to help:

1) Read and share! Find out more about problems facing the ocean, including coral reefs and ecosystems found locally. Keep up-to-date on information regarding climate change; our knowledge is constantly changing, and it’s important to keep informed in order to stay connected with the problems facing our world and share what you know with others.
2) Write! Become an advocate for ocean protection. You can write to elected officials, newspapers, and even your friends, sharing your knowledge with others and urging them to make sure that they are doing their part to protect the ocean, both locally and globally. Also, be sure to remember to thank those organizations that already work to protect the ocean.
3) Respect the ocean! Get involved in local beach clean-ups, and remember to keep the beach and ocean clean and safe for the animals that call them home. Don’t buy coral products, whether in jewelry or in your fish tank. Be aware that the choices you make—from the food you eat to the lightbulbs you use—have the power to make change.

To learn more, visit:

Coral Reef Alliance
National Geographic – Coral
National Geographic – The Ocean
National Oceanic and Atmospheric Administration’s Coral Reef Conservation Program
Ocean Conservancy