Coral reef survival

New research predicts the damage from increased carbon dioxide in the oceans

University of Hawaiʻi at Mānoa
Tara Hicks Johnson, (808) 956-3151
School of Ocean and Earth Science and Technology
Posted: Sep 19, 2005

VIRGINIA KEY, FL — Increases in carbon dioxide are bad for corals — no matter how you look at it. That‘s the conclusion of two researchers in the September issue of the Journal of Geophysical Research-Oceans, who investigated the effects of doubling carbon dioxide on two coral species that are important reef builders in Kaneohe Bay, Hawaii.

"The ocean is known to absorb carbon dioxide, causing measurable changes in seawater chemistry of the surface ocean," said Chris Langdon, associate director of the National Center for Caribbean Coral Reef Research and one of the paper‘s authors. "If this process continues to increase at the current rate, we expect carbon dioxide levels (and consequently the acidity of the ocean) to increase 200-300 percent in the next 50-100 years, so it is important to learn how these changes might affect marine ecosystems."

Corals were studied in this gutter-like flume at the Hawaii Institute of Marine Biology. (Image: Marlin Atkinson, HIMB/SOEST)

Langdon and his colleague and co-author, Marlin Atkinson from the Hawaii Institute of Marine Biology at the University of Hawaii at Manoa, found that this manipulation of seawater chemistry, carefully designed to mimic conditions that might happen in the next 50 to 100 years, significantly damaged coral. Langdon and Atkinson observed a 50 percent decrease in skeletal growth at the same time that the photosynthesis of the guest algae within the coral increased. The results indicate a breakdown in the normally mutually beneficial relationship between this guest algae and host coral. A similar breakdown has been widely reported when corals are exposed to elevated nutrient concentrations. Competition for carbon between the algae and the coral may be the explanation, Langdon said.

"As much as we could, we tried to account for other environmental changes known to affect coral growth, such as conducting our experiments in both summer and winter to explore possible interactions between elevated carbon dioxide and seasonal change in temperature and light and by first exposing the corals to an elevated nutrient loading," Langdon said.

While this study did not examine the effects of elevated water temperature associated with global warming, this is also known to be a result of increased carbon dioxide levels in the atmosphere. Scientists predict global ocean temperatures to increase two to five degrees Celsius by the year 2100. "Because many species of coral are already growing very near their thermal threshold, any warming will reduce their growth," Langdon said. "The combined effects of global warming and ocean acidification on coral growth could be even worse than what we observed in our study. A major unknown is whether corals possess the capacity to adapt or acclimate to these environmental changes, if the rate of change is not too fast."

Atkinson said, "The recent research on carbon dioxide and corals has led to increased awareness that coral reefs may be more affected by global processes such as climate change, rather than by local small-scale impacts such as freshwater runoff."

The National Oceanic and Atmospheric Administration (NOAA) National Sea Grant Program, University of Hawaii, the David and Lucille Packard Foundation, and a generous gift by Edward P. Bass to the Biosphere 2 Center funded this research.

For Interviews contact:

Marlin J Atkinson

Hawaii Institute of Marine Biology

PO Box 1346 Coconut Island

Kaneohe, HI 96744 USA

ph: 808-235-2224


PO Box 1873 Seward Ak 99664

ph: 907-224-3538 fx: 907-224-5791


School of Ocean and Earth Science and Technology

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The School of Ocean and Earth Science and Technology (SOEST) was established by the Board of Regents of the University of Hawaii in 1988. SOEST brings together in a single focused ocean, earth sciences and technology group, some of the nation‘s highest quality academic departments, research institutes, federal cooperative programs, and support facilities to meet challenges in the ocean and earth sciences. Scientists at SOEST are supported by both state and federal funds as they endeavor to understand the subtle and complex interrelations of the seas, the atmosphere, and the earth.

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