Why should we care about ocean acidification?

Natalie Freeman, a PhD candidate in the Atmospheric and Oceanic Sciences department, studies the effects of ocean acidification on microscopic shell-making organisms known as coccolithophores—the same organisms that form England’s famed White Cliffs of Dover. She often has to explain why we should care we about the acidification of our oceans.

“If I’m on an airplane and I say what I do, I usually talk about how the ocean takes up a lot of carbon … [which] affects the organisms living in the ocean. And they’re important because they feed all of the fish we eat and they also give you every second breath.”


So how does ocean acidification affect the marine ecosystems we depend on? Let’s go back to my Sour Skittles example from Part 1. Eating a bag normally—you know, without waiting for the citric acid to dissolve on your tongue—might leave your tongue feeling tingly but no worse for the wear. Similarly, slightly increasing the acidity of the oceans may not be a big deal. But as we continue to burn fossil fuels and increase the acidity of oceans (p.11), we will begin to see drastic consequences, particularly to the plants and animals that dwell there.

Sea creatures with calcium carbonate shells, such as corals, mollusks, and some phytoplankton, are especially vulnerable to ocean acidification. Calcium carbonate reacts with acids so when shelled organisms are forced to live a high acid environment they either develop their shells slower, or spend so much more energy attempting to grow that they are unable to reach their typical size or even reproduce.


A pteropod shell placed in increasingly acidic seawater begins to dissolve after 45 days. Credit:  Smithsonian Institution’s Ocean Portal

One of those tiny creatures with a calcium carbonate shell is phytoplankton, which provide the base of our marine food web and help maintain biodiversity. If phytoplankton are unable to grow and develop normally, there would likely be huge consequences on the fish and seafood that we eat.

Not only are we dependent on phytoplankton for our food, but for life-giving oxygen as well. According to Freeman, phytoplankton are responsible for half of the oxygen we breathe every day. We’re indebted to these tiny organisms, even here in Colorado.


Coral dying over the course of a year in the America Samoa. Credit:  Nature

And phytoplankton aren’t the only creatures feeling the direct effects of ocean acidification. Our fragile coral reefs are also vulnerable to the increasing acidity.

If the simple loss of such a beautiful part of our world doesn’t tug at your heartstrings, consider the economic impacts– according to NOAA, about half of all federally managed fisheries depend on coral reefs. The commercial value of coral reefs to the U.S. fishing industry is estimated at over $100 million, and this doesn’t even touch on the billions of tourism dollars funneled into the local economies near coral reefs.

Ocean acidification has also already been identified as having contributed to a massive oyster die-off in the Pacific Northwest, and is creating dramatic impacts on the $110 million per year oyster industry.

We can point to a lot of ways ocean acidification has already hurt our ecosystems, but what will happen if the process continues?

Freeman and her colleagues understand that the exact effects of ocean acidification on marine organisms and their ecosystems are far from predictable, but they also know the effects will have an impact. “There’s going to be shifts in [vulnerable organisms’] sizes, their distribution, where they usually are … if the water is going to change their temperature, small to large, which ones dominate, maybe decreased biodiversity … that’s why ongoing and continued ocean acidification research is so important.”

Why should we care about ocean acidification? Because the ocean gives us every second breath, and we’re in danger of cutting off our air supply.

By Ryan Harp

Posted by Science Buffs

A CU Boulder STEM Blog

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