St. Petersburg Coastal and Marine Science Center
Research: Coral Reef Community Calcification and Metabolism
As carbon dioxide (CO2) increases in the atmosphere, CO2 is absorbed by the surface water of the ocean where it combines with water (H2O) to make a naturally occurring, weak acid called carbonic acid (H2CO3). This process, called ocean acidification, results in an increase in the acidity of seawater (and a decrease in pH). A number of experimental and modeling studies (e.g. Kleypas et al., 1999; Marubini and Atkinson, 1999; Langdon et al., 2000; among many others) indicate that ocean acidification will result in a decrease in rates of calcification by reef organisms, and an increase in dissolution of reef sediments that form the foundation of reef structure. A 40% decrease in coral reef calcification has been hind-cast between the years 1880 and 2065. The severity of the impact to coral reefs will depend in part upon the balance between calcification (production of reef structure) and dissolution of reef sediments, and whether or not reef systems will be able to keep up with rising sea level.
The Submersible Habitat for Analyzing Reef Quality (SHARQ) is a large, underwater incubation chamber used to measure changes in water chemistry resulting from metabolic activity of reef organisms and plants living on the seafloor. [larger version]
USGS coral reef studies (Yates and Halley 2003, 2006a and b, Yates et al. 2007) have focused on quantifying reef health in terms of basic processes such as their ability to grow and keep up with rising sea level, and on the response of these processes to changes in seawater chemistry that result from climate change and ocean acidification. Results of these studies indicate that by the year 2100, net sediment dissolution may exceed carbonate production at reef ecosystems in Florida, the Caribbean, and the Pacific resulting in degradation of coral reefs, loss of fish habitat, and increased coastal erosion. Assessing the resiliency of reefs to climate change and preparing coastal resource managers for the inevitable effects of climate change and rising sea level requires a comprehensive look at past, present, and future coral reef calcification and growth rates in response to elevated atmospheric CO2 and changing ocean chemistry.
This task focuses on forecasting and hind-casting the future and past response of coral reef calcification and growth to changes in seawater carbonate chemistry from pre-industrial time to the year 2100. This will be accomplished by:
- Determining modern-day rates of coral reef community calcification relative to ocean chemistry,
- Measuring the response of coral reef community calcification to future, elevated levels of carbon dioxide and lower pH through experiments performed in natural reef habitats, and
- Reconstructing past changes in seawater pH relative to coral growth rates using stable isotope geochemical techniques (δ11B and δ18O) and changes in coral skeletal density in coral skeleton cores (in coordination with USGS Mendenhall Fellowship Research Studies (R. Moyer) and the Climate Change Task).
The combined results of these three task elements will provide one of the first comprehensive records of historical, modern day, and future coral reef calcification/growth rates relative to changing seawater pH and pCO2, and the basis for developing capabilities for predicting the impact of ocean acidification on coral reef ecosystem resiliency. This task was developed in partnership with NOAA, NCAR, University of Miami-RSMAS, and USF; with collaborators from UPR, the Buccoo Reef Trust, Tobago House of Assembly, Caribbean Coral Reef Institute, and University of the West Indies. Results of these studies will support work of partnering agencies to develop predictive capabilities for quantifying the impacts of elevated pCO2 on coral reefs.
Kleypas, J.A., Buddemeier, R.W., Archer, D., Gattuso, J.P., Langdon, C., and Opdyke, B.N. 1999. Geochemical consequences of increased atmospheric carbon dioxide on coral reefs. Science 284:118-120.
Langdon, C. and others. 2000. Effect of calcium carbonate saturation state on the calcification rate of an experimental coral reef. Global Biogeochemical Cycles 14:639-654.
Marubini, F. and Atkinson, M.J. 1999. Effects of lowered pH and elevated nitrate on coral calcification. Marine Ecology Progress Series 188:117-121.
Yates, K.K. and Halley, R.B. 2003. Measuring coral reef community metabolism using new benthic chamber technology. Coral Reefs 22:247-255.
Yates, K.K. and Halley, R.B. 2006. Diurnal variation in rates of calcification and carbonate sediment dissolution in Florida Bay. Estuaries and Coasts 29:24-39.
Yates, K.K. and Halley, R.B. 2006. CO32- concentration and pCO2 thresholds for calcification and dissolution on the Molokai reef flat, Hawaii. Biogeosciences 3:1-13.
Yates, K.K., Dufore, C., Smiley, N., Jackson, C., and Halley, R.B. 2007. Diurnal variation of oxygen and carbonate system parameters in Tampa Bay and Florida Bay. Marine Chemistry 104:110-124.