The Impact of pH on The Impact of pH on ppCOCO22 Levels in Florida Levels in Florida

LakesLakes

Jenney L. KelloggJenney L. Kellogg

Florida LAKEWATCHFlorida LAKEWATCHDept. of Fisheries and Aquatic SciencesDept. of Fisheries and Aquatic Sciences

University of FloridaUniversity of FloridaGainesville, FLGainesville, FL

IntroductionIntroduction

Growing research dealing with Growing research dealing with supersaturation of carbon dioxide in supersaturation of carbon dioxide in freshwater systems. (Cole et al. 1994)freshwater systems. (Cole et al. 1994)

Focus on heterotrophy in lakes.Focus on heterotrophy in lakes.

ObjectivesObjectives

Evaluate Evaluate ppCOCO22 levels in Florida Lakes. levels in Florida Lakes.

Examine factors that may influence Examine factors that may influence ppCOCO22

levels in Florida Lakes.levels in Florida Lakes.

Data AvailableData Available

667 Lakes 667 Lakes 4730 samples taken4730 samples taken 1979-1996 year range1979-1996 year range

Variable Mean Min Max MedianTotal Phosphorus (µg/L) 46 0.7 1221 17Total Nitrogen (µg/L) 860 23 5900 704Chlorophyll a (µg/L) 17 0.5 300 6Secchi (m) 2 0 7 1.5Color (Pt-Co units) 52 0 690 24pH 6.7 3.9 11.7 6.8Total Alkalinity (µequiv/L) 500 0 460000 243Specific Conductance (µS/cm) 192 11 7200 121

Summary of Lake ConditionsSummary of Lake Conditions

MethodsMethods

Data were compiled from various studies Data were compiled from various studies conducted in Florida from 1979-1996. (Canfield conducted in Florida from 1979-1996. (Canfield 1981, Canfield and Hoyer 1992, Florida 1981, Canfield and Hoyer 1992, Florida LAKEWATCH 1993,1996, and Greis 1995) LAKEWATCH 1993,1996, and Greis 1995)

Data included pH, Total Alkalinity, Specific Data included pH, Total Alkalinity, Specific Conductance, TP, TN, Chloride, Silicon, Sulfate, Conductance, TP, TN, Chloride, Silicon, Sulfate, Calcium, Magnesium, Sodium, Potassium, Iron, Calcium, Magnesium, Sodium, Potassium, Iron, Chlorophyll, Color, and Secchi Depth.Chlorophyll, Color, and Secchi Depth.

MethodsMethods

pCOpCO2 2 measured indirectly using:measured indirectly using:Total Alkalinity (Total Alkalinity (µequiv/L)µequiv/L)Specific Conductance (µS/cm)Specific Conductance (µS/cm)pHpHWater Temperature (°C)Water Temperature (°C)

Correlation AnalysisCorrelation AnalysisModel the effects of changes in pH, Model the effects of changes in pH,

Alkalinity, Temperature and Specific Alkalinity, Temperature and Specific ConductanceConductance

Frequency Distribution of pCO2 (atm )

Log10 pCO2 (atm)

100 101 102 103 104 105 106

Nu

mb

er

of

La

ke

s

0

10

20

30

40

50

60

Undersaturated Supersaturated

Atm

ospher ic C

oncen

tratio

n

Variable Correlation CoefficientTotal Phosphorus (µg/L) -0.3038Total Nitrogen (µg/L) -0.352Chlorophyll a (µg/L) -0.4777

Variable Correlation CoefficientColor (Pt-Co units) 0.0935

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

ConclusionsConclusions

80% of Florida lakes sampled were 80% of Florida lakes sampled were supersaturated with carbon dioxide.supersaturated with carbon dioxide.

pH is the controlling factor for indirectly pH is the controlling factor for indirectly measured levels of measured levels of ppCOCO2 2 in Florida in Florida

freshwater lakes.freshwater lakes.

Is Is ppCOCO22 controlling pH or is pH controlling controlling pH or is pH controlling

ppCOCO22??

pH is the controlling factor for measured pH is the controlling factor for measured levels of levels of ppCOCO2.2.

Other Processes Leading to Other Processes Leading to Excess COExcess CO22

Net heterotrophy at the ecosystem scale.Net heterotrophy at the ecosystem scale. Injection of COInjection of CO22 rich groundwater. rich groundwater.Precipitation of dissolved carbonates.Precipitation of dissolved carbonates.Mixing of an in-lake source of acidity with Mixing of an in-lake source of acidity with

an input of bicarbonate.an input of bicarbonate.Emergent macrophytesEmergent macrophytes

Other ConsiderationsOther Considerations

Lakes supersaturated with Lakes supersaturated with ppCOCO22 may not may not

be heterotrophic.be heterotrophic.

AcknowledgementsAcknowledgements Florida LAKEWATCHFlorida LAKEWATCH NALMS Student Travel GrantNALMS Student Travel Grant Dr. Canfield, Mark Hoyer, Dr. Roger Dr. Canfield, Mark Hoyer, Dr. Roger

Bachmann, Department of Fisheries and Bachmann, Department of Fisheries and Aquatic Sciences, University of Florida; Aquatic Sciences, University of Florida; Florida LakewatchFlorida Lakewatch

Carlos Duarte, ICarlos Duarte, IMEDEA (CSIC-UIB), MEDEA (CSIC-UIB), Instituto Mediterráneo de. Estudios Instituto Mediterráneo de. Estudios AvanzadosAvanzados

Yves Prairie, Yves Prairie, Département des Sciences Département des Sciences biologiques, Université du Québec à biologiques, Université du Québec à MontréalMontréal

Any Questions?Any Questions?