Effects of Climate Change on Corals in Florida Bay

Chris Langdon, Remy Okazaki, Peter Swart

Rosenstiel School of Marine and Atmoshperic Science

University of Miami

Scientists working from the Keys Marine Lab are doing their part to investigate the effects of climate change, in particular, the phenomenon of ocean acidification. The University of Miami (UM) scientists are studying two species of corals growing in Florida Bay and whether these corals may have adapted to changing CO2. These star and starlet corals appear to be healthy and growing without any detrimental effects, despite the fact that Florida Bay’s highly variable environment makes it a potentially harsh habitat for corals and other organisms. Because of Florida Bay’s unique environment and environmental variability, it is an ideal “natural laboratory” to study climate change and corals.

Florida Bay experiences daily, seasonal, and regional fluctuations in many water chemistry parameters, including salinity, pH, and CO2. As a consequence of these changing parameters, the bay experiences extreme conditions, including CO2 levels that can be twice as high as levels that are found at the reefs on the Keys. These high-CO2 times in Florida Bay mimic future predicted conditions for the world’s oceans as greenhouse gas emissions continue to increase. As more and more CO2 builds up in the atmosphere, more of it fluxes into the oceans where it becomes carbonic acid. This is the concept of ocean acidification. This acid neutralizes carbonate ions in the ocean, which marine calcifiers, such as corals, require to build their skeletons. Consequently, calcification is slowed. With their ability to calcify and grow impaired, corals are more susceptible to erosion, storm damage, and other processes that break down reefs. Hence, coral reefs and the ecosystem services they provide are threatened by ocean acidification.

Based out of the Keys Marine Lab, the UM scientists are measuring coral calcification and photosynthesis in a wide array of environmental conditions. Additionally, the scientists are analyzing a 190-year old coral skeleton from the study site to reconstruct the water chemistry and determine how the coral has grown during the last two centuries. These experiments should indicate whether corals have indeed adapted or acclimated to changing CO2. If they have, then hope exists for corals in the future.

(photo: This core sample is from a star coral skeleton and represents ~50 years of growth. Scientists will attempt to reconstruct the history of Florida Bay from this skeleton.)