1 / 24

Seasonal Patterns of Oxygen in Lakes: Factors, Variations, and Biological Implications

Explore the dynamics of oxygen levels in lakes, factors influencing oxygen availability, and biological consequences. Discover the seasonal patterns associated with stratification and insights into the oxygen cycle. Learn about the solubility of gases in water and its impact on aquatic life.

deleonr
Download Presentation

Seasonal Patterns of Oxygen in Lakes: Factors, Variations, and Biological Implications

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Oxygen and CO2 • Announcements • Openings for canoe trip? • Exams will be passed back on Monday • Project proposals due this afternoon at 5 (my office!) • Include: • Question/hypothesis & why its interesting/important • Expected results • Methods • Materials • 2 pages max • The more info you include, the more feedback you will get • Think about statistics and replicate samples

  2. Seasonal patterns associated with stratification

  3. Seasonal patterns in O2

  4. Sources and sinks of oxygen • Atmosphere • Photosynthesis • Decomposition • Respiration

  5. Depth Biomass Photosynthesis Photosynthesis distribution = specific primary production * light climate * algae biomass Mesotrophic epilimnion (well mixed) Eutrophic with surface bloom Oligotrophic with max. biomass at metalimnion (positive heterograde curve) Shallow transparent lakes with max. biomass on bottom

  6. Hypolimnetic oxygen depletion rates • Depends on • The amount of oxygen present at the beginning of summer stratification • Length of stratification period • The amount of organic matter rain from the photo zone (& therefore the amount of decomposition) • The volume of the hypolimnion

  7. Lake A Lake B Production Decomposition Hypolimnetic depletion rates

  8. Factors that influence O2 availability • Solubility • Very slow diffusion • Deviations from the theoretical amount of O2 that can dissolve into water • Depletion of O2 during respiration/decomposition • Oversaturation of O2 during high rates of photosynthesis in dense plant beds or phytoplankton communities

  9. For O2, 260 µmol/L = 8.32 mg/L which is atmospheric saturation at 25oC Northgate is supersaturated with CO2 (atmospheric saturation is 14 µ mol/L) Cranberry shows huge diel changes in CO2 and O2 concentrations Note: Dystrophy: low production lake associated with high humic content (dissolved organic carbon) Diel variations in CO2 and O2 From a manuscript entitled “Lake metabolism: Relationships with dissolved organic carbon and chlorophyll” by Paul C. Hanson, Darren L. Bade, Stephen R. Carpenter, Timothy K. Kratz

  10. Inorganic carbon light CO2 O2 H2C O P HC OH ATP C O organic carbon in a molecule of phosphoglycerate Light rxns Dark rxns O- Diel patterns… Day-time photosynthesis produces O2 6CO2 + 6H2O (light)  C6H12O6 + 6O2 Night-time respiration uses O2 and produces CO2 C6H12O6 + 6O2 6CO2 + 6H2O + energy (ATP)

  11. Oxygen depletion or overstaturation in dense Eurasion water milfoil beds

  12. Oxygen depletion in dense Trapa beds in the Hudson River

  13. Solubility of gases in water Henry’s Law: the solubility of a gas in a liquid is directly proportional to the pressure of the gas over the liquid Partial Pressuregas = khMgas Kh =Henry’s Law constant Mgas = molarity (moles of gas per liter of water)

  14. Maximum solubility Compute the (maximum) solubility of O2 in water that is in equilibrium with air at 25oC and 1 atm (sea level). kh(O2) = 780 atm/M PO2 = 0.20 atm Solubility expressed as: MO2 = PO2/kh(O2) = 0.2 atm/780 atm/M = 0.00026 M O2 mg/L = 0.00026 moles/liter*32 g O2/mol = 8.32 mg/L

  15. Notice that we’ve specified 1) temperature & 2) atmospheric pressure 3) Increased salinity also reduces oxygen solubility

  16. Biological consequences?? • Less O2 available when temperatures are high and metabolic demands are high • Influences distribution of organisms for Ex: Fish oxygen tolerances • at least 2 - 5 mg O2/l for epilimnetic species • at least 5 - 9 mg O2/l for cold-water species • sustained hypoxia (< 2 mg O2/l) generally lethal

  17. What area of Dudley Lake is available for fishes in Early October??

  18. www.liv.ac.uk/lstm/ pvbd/Moslarva.jpg members.aol.com/mkohl1/Images/ PhysellaLive300.jpg http://www.dec.state.ny.us/website/dow/stream/empfamilies.htm www.ento.csiro.au/.../insects/ images/dragonfly_nymph2.jpg Biological adaptations for obtaining O2

  19. europa.eu.int/comm/research/ success/images/0261a.jpg

  20. Winterkill lakes • Small, shallow lakes • Anoxic during ice-cover (why?) • Have distinctive fish assemblages • Why?

  21. Mystery Lake inlet See Magnuson et al. 1985. Surviving winter hypoxia… Environmental biology of fishes 14(4):241-250

  22. Winterkill lakes X • Different species had different behaviors • Leave the lake • Move towards inlet • Move towards ice/water interface • Breathe bubbles • In some cases, smaller fish less tolerant • Fish that typically winterkill (bluegill) don't exhibit these behaviors • See Magnuson et al. 1985. Surviving winter hypoxia… Environmental biology of fishes 14(4):241-250

  23. Oxygen in running waters • At saturation in small, turbulent streams • In areas where currents have slowed, oxygen can be altered by photosynthesis or respiration • Seasonal inputs of organic material or nutrients can result in high decomposition rates and low O2 • Leaf-fall • Runoff with nutrients from golf-courses, lawns, ag fields • Organic sewer (yum) • Diel variation potentially greater in slow-flowing, nutrient enriched streams & rivers

More Related