10 ChemMatters | FEBRUARY/MARCH 2018 www.acs.org/chemmatters
ALEXA ADJUSTS HER SNORKEL, MASK, AND FINS AS SHE PREPARES TO plunge into clear, blue water. She and four other U.S. high school students are two miles from Isla Ballena, an island off the Pacific coast of Costa Rica. The waters surround- ing the island—part of Costa Rica’s Marino Ballena National Park—contain coral reefs that attract visitors from around the world. The students are attending Ocean Camp, a university-sponsored two-week research program that exposes students to
oceanography and marine biology. Here, Alexa and her classmates will learn firsthand about
marine life, as well as check the health of the reefs and 18 species of coral.
Along with their instructors and a snorkeling guide, the
students swim past swaying tentacle-like coral polyps and
colorful fish. All the while, they watch closely for corals that
have faded color or that seem to be weakened or crumbling.
Alexa and her classmates have learned that these are signs
of unhealthy corals, which are being threatened by warming
and increasingly acidic oceans due to rapid changes in the
Earth’s climate. Although corals typically thrive in warm water,
it places too much stress on them if the ocean gets too warm.
This causes them to lose their beautiful colors and turn white,
as if bleached. And a more acidic ocean can make it harder for
corals to get the materials they need to grow and that causes
them to weaken and crumble.
This is concerning because although coral
reefs make up less than 1% of the Earth’s
surface, they play a crucial role in the ocean
ecosystem—corals provide shelter for perhaps
a quarter of the ocean’s species. This is why
researchers study changing ocean waters and
ask the important question: How will a warmer
and more acidic ocean affect corals and what
does that mean for the health of our oceans?
The greenhouse effect
One of the lessons Ocean Camp instructors
gave earlier that week covered climate change
and how it affects the ocean. A culprit
behind ocean warming and acidification is an increase in carbon dioxide in
the atmosphere. Carbon dioxide and
other gases play a crucial role in the
Earth’s climate in what is called the
greenhouse effect: without them, the
planet would be cold and inhospitable.
These atmospheric gases and a greenhouse
work in quite different ways, but the resulting
effect, higher temperatures in both cases, has
led to this description. Although this term is
misleading, it is commonly used.
A greenhouse is a building that is heated
with solar radiation so that it can stay warm
even in winter. Light from the sun passes
through the glass roof to heat plants and the
ground inside the greenhouse. These objects
then emit infrared radiation, that is heat. Thermal energy is trapped in the greenhouse, keep-
How Carbon Dioxide Is
Changing the Oceans
By George Hale
Scan the image of the
coral reef below with
mobile app to