Diurnal and seasonal variation of coastal carbonate system parameters in South Florida and the Caribbean

Assessing the impact of climate change and ocean acidification on coastal and marine ecosystems requires accurate characterization of its chemical and physical effects on the carbonate system in seawater. Very few data exist that characterize natural variations in coastal carbonate chemistry, limiting the development and validation of coastal climate change and ocean acidification models. We measured carbonate system parameters over diurnal cycles in shallow, coastal ecosystems of Florida Bay, Tampa Bay, Biscayne National Park, Puerto Rico, the U.S. Virgin Islands, Tobago, and the Bahamas. Salinity, temperature, and dissolved oxygen were measured continuously, and seawater samples were collected every 4 hours throughout multiple 24-hour time periods. Total alkalinity and pH were measured using spectrophotometric techniques, dissolved inorganic carbon was measured via carbon coulometry, and remaining carbonate system parameters were calculated using CO2SYS. Seasonal variability was either determined from existing data sets, or modeled using salinity and temperature data collected from CTDs deployed at study locations or long-term monitoring sites. Results indicate that all carbonate system parameters showed distinct variation over diurnal timescales primarily due to productivity, respiration, and precipitation and dissolution of calcium carbonate. The average range of diurnal variation was up to 102% of the seasonal range of variability in carbonate chemistry. Our data indicate that use of seasonal data sets without careful consideration of diurnal variability (or vice versa) may impart significant error in calculation of annual carbon budgets and modeling carbon cycling in coastal ecosystems. Implications for modeling long-term impacts of ocean acidification in coastal ecosystems will be discussed.

Yates, K. & Smiley, N. A., 2010. Diurnal and seasonal variation of coastal carbonate system parameters in South Florida and the Caribbean. American Geophysical Union, Fall Meeting 2010, abstract #OS31E-05. Abstract.

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