Mesoamerican Reef

The Mesoamerican Reef is one of the largest reefs in the world, second only to the Great Barrier Reef. The reef spans nearly 700 miles from the northern tip of Mexico’s Yucatan Peninsula to the Bay Islands of Honduras. It covers 115 million acres and includes ocean habitats, coastal zones and tropical and cloud forests. There are more than 60 species of coral and 500 species of fish in the reef. It is also home to the whale shark, the world’s largest fish.

Reefs are formed from tiny animals called coral and are often referred to as "coral reefs." Although they are animals, coral are immobile. They live in colonies called polyps. Calcium carbonate secreted from the base of the polyps serve as the skeletal structure of coral. Over time, these calcium carbonate secretions build up to form reefs. Reefs vary in size and appearance according to the specific species of coral building them. But a common feature of virtually all reef-dwelling coral is their symbiotic, or mutually beneficial, relationship with the algae zooxanthellae. Zooxanthellae algae play a vital role in the health of coral. The algae benefit from the protection and access to sunlight provided by living in the coral and the coral receive food from the algae’s photosynthetic processes.

Reefs serve two important functions. They provide habitat for a variety of organisms that rely on them for food and shelter. They also function as natural barriers to storms and coastal erosion.

Reefs are also very sensitive to environmental stress. The Mesoamerican Reef and other reefs around the world are being affected by climate change. Climate change impacts the ocean’s pH and temperature. The ocean acts as a carbon sink, absorbing 30 to 50 percent of all carbon dioxide emissions worldwide. These increased levels of carbon dioxide have caused the pH of the ocean to drop from 8.2 to 8.1 in the last century and have contributed to an ocean surface temperature increase of one degree Celsius.

While these impacts may seem small, the environmental stress of these temperature and pH changes cause a phenomenon known as coral bleaching. When coral polyps are stressed they release their zooxanthellae algae. In the absence of this symbiotic partner coral weaken, become more prone to disease and often die. This event is called coral bleaching because algae give coral their color. Coral whiten when algae are released. The Mesoamerican Reef has experienced two mass bleachings in recent history. In 1995, a bleaching killed about 10 percent of coral in the Mesoamerican Reef. A bleaching in 1998 killed nearly 50 percent.

Related Resources:

Speed of Sound is Changing in an Acidic Ocean (Physics, Environmental Science, Chemistry, Science)

Oceanographic Specialties (Physics, Environmental Science, Earth Science, Biology, Science)

Multi-Faceted Approach to Studying Climate Change (Science, World History, Economics, Earth Science, Social Studies, Environmental Science)

Photo: Michael Baird