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The Impact of pH on p CO 2 Levels in Florida Lakes. Jenney L. Kellogg Florida LAKEWATCH Dept. of Fisheries and Aquatic Sciences University of Florida Gainesville, FL. Introduction. Growing research dealing with supersaturation of carbon dioxide in freshwater systems. (Cole et al. 1994)
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The Impact of pH on pCO2 Levels in Florida Lakes Jenney L. Kellogg Florida LAKEWATCH Dept. of Fisheries and Aquatic Sciences University of Florida Gainesville, FL
Introduction • Growing research dealing with supersaturation of carbon dioxide in freshwater systems. (Cole et al. 1994) • Focus on heterotrophy in lakes.
Objectives • Evaluate pCO2 levels in Florida Lakes. • Examine factors that may influence pCO2 levels in Florida Lakes.
Data Available • 667 Lakes • 4730 samples taken • 1979-1996 year range
Methods • Data were compiled from various studies conducted in Florida from 1979-1996. (Canfield 1981, Canfield and Hoyer 1992, Florida LAKEWATCH 1993,1996, and Greis 1995) • Data included pH, Total Alkalinity, Specific Conductance, TP, TN, Chloride, Silicon, Sulfate, Calcium, Magnesium, Sodium, Potassium, Iron, Chlorophyll, Color, and Secchi Depth.
Methods • pCO2 measured indirectly using: Total Alkalinity (µequiv/L) Specific Conductance (µS/cm) pH Water Temperature (°C) • Correlation Analysis • Model the effects of changes in pH, Alkalinity, Temperature and Specific Conductance
Undersaturated Supersaturated Atmospheric Concentration
G. E. Hutchinson. 1975. A treatise on limnology, volume 2, part 2. Wiley, New York. C. Juday, E. A. Birge & W. W. Meloche. 1935. The carbon dioxide and hydrogen ion content of the lake waters of northeastern Wisconsin. Wisconsin Academy of Sciences, Arts, and Letters
Conclusions • 80% of Florida lakes sampled were supersaturated with carbon dioxide. • pH is the controlling factor for indirectly measured levels of pCO2 in Florida freshwater lakes.
Is pCO2 controlling pH or is pH controlling pCO2? pH is the controlling factor for measured levels of pCO2.
Other Processes Leading to Excess CO2 • Net heterotrophy at the ecosystem scale. • Injection of CO2 rich groundwater. • Precipitation of dissolved carbonates. • Mixing of an in-lake source of acidity with an input of bicarbonate. • Emergent macrophytes
Other Considerations • Lakes supersaturated with pCO2 may not be heterotrophic.
Acknowledgements • Florida LAKEWATCH • NALMS Student Travel Grant • Dr. Canfield, Mark Hoyer, Dr. Roger Bachmann, Department of Fisheries and Aquatic Sciences, University of Florida; Florida Lakewatch • Carlos Duarte, IMEDEA (CSIC-UIB), Instituto Mediterráneo de. Estudios Avanzados • Yves Prairie, Département des Sciences biologiques, Université du Québec à Montréal