Zoology 315: Limnology Oxygen, CO2, pH, and ANC Abby Popp June 26th, 2006 1. A brief word on depth profiles 2. And lake layers a. Epilimnion b. Metalimnion c. Hypolimnion OXYGEN, CARBON DIOXIDE, AND PHOTOSYNTHESIS All about O2 All about CO2 Solubility of O2 & CO2Sources and Sinks of O2 and CO2 1. Atmospheric diffusion: Flux = k*(O2eq-O2conc) Units: Flux = moles/m2*d Negative flux: Positive flux: 2. Photosynthesis & respiration Oxygen Profiles clinograde orthograde pos. heterograde neg. heterogradeTemporal variation in O2 Lake trophic status: Eutrophic: Oligotrophic: Dystrophic: Trophic status and oxygen dynamics: Metabolism Gross Primary Production (GPP): Respiration (R):Net Primary Production (NPP): Net Ecosystem Production (NEP): Positive NEP => Negative NEP => Thought Questions 1. Why are clinograde oxygen profiles more common in temperate lakes than orthograde profiles? Under what conditions would you find an orthograde profile? 2. If production<respiration (P<R) in a lake (in other words, if the plants aren’t making enough food), what are some possible sources of organic material that could be fueling respiration? MOVING ON: PH, INORGANIC CARBON AND ACID NEUTRALIZING CAPACITY pH: puissance d’hydrogène log scaleDissociation constant of water, Kw Kw = [H+][OH-] = 10-14 (Remember: when multiplying numbers with exponents, add exponents) pH = negative log of hydrogen ion concentration pH extremes: bogs: acid mine drainage: alkaline waters (soda lakes): Dissolved Inorganic Carbon (DIC): CO2 = H2CO3 = HCO3- = CO3-2 = DIC =The carbonate system The magical important equation: Forms of DIC are related to pH: Lake A has a pH of 5. What is the major form of DIC in this lake? Lake B has a pH of 9.5. What is the major form of DIC in this lake? Acid Neutralizing Capacity (ANC) Water’s ability to buffer pH change Also called… ANC = [HCO3-] + 2[CO3-2] + [OH-] – [H+]Processes affecting inorganic carbon 1. Atmospheric Exchange 2. Groundwater / Weathering 3. Metabolism CaCO3 precipitation: Whiting Event: High rates of photosynthesis cause… Which leads to… Travertine: The carbonate
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