Presentation on theme: "Lab 12: Dissolved Oxygen Mr. West Bell Ringer:"— Presentation transcript:
1 Lab 12: Dissolved Oxygen Mr. West Bell Ringer: “Why did fish that I kept in an aquarium over my radiator die? An aerator was producing a constant stream of bubbles, so they should have had plenty of oxygen."Lab 12: Dissolved OxygenMr. WestLet's begin by looking at factors that influence the availability of oxygen…Adapted from:
2 Oxygen is essential for cellular respiration in most organisms factors that affect amount of dissolved O2 in water:temperatureas water temperature, its ability to hold O2 decreasesphotosynthetic activityin bright light, aquatic plants produce more O2decomposition activityas organic matter decays, microbial respiration consumes O2mixing & turbulencewave action, waterfalls & rapids aerate H2O & O2salinityas water becomes more salty, its ability to hold O2 decreases
3 Primary ProductivityRate at which plants and other photosynthetic organisms produce organic compounds in an ecosystem.Gross productivity = the entire photosynthetic production of organic compounds in an ecosystemNet productivity = the organic materials that remain after photosynthetic organisms in the ecosystem have used some of these compounds for their cellular energy needs (cellular respiration).
4 Lab 12: Dissolved Oxygen primary productivity measured in 3 ways: amount of CO2 usedrate of sugar (biomass) formationrate of O2 production
5 Measuring O2 saturation: Using a Nomograph To measure how much oxygen water can hold (saturation), you need to be able to read a nomograph.Many kits and testing procedures are available for measuring dissolved oxygen.
6 Lab ProcedureMonitor the effect of varying light levels on dissolved oxygen in an algae-rich water cultureAmount of light available for photosynthesis drops off sharply with increasing depth in an aquatic environmentCan model this condition by wrapping water-sample bottles with increasing layers of screen
8 Lab 12: Dissolved Oxygen Conclusions temperature = dissolved O2 light = photosynthesis = O2 productionO2 loss from respirationrespiration = dissolved O2 (consumption of O2)
9 FRQ 2001A biologist measured dissolved oxygen in the top 30 centimeters of a moderately eutrophic (mesotrophic) lake in the temperate zone. The day was bright and sunny and the wind was calm. The results of the observation are presented below.Using the graph paper provided, plot the results that were obtained. Then, using the same set of axes, draw and label an additional line/curve representing the results that you would predict had the day been heavily overcast.Explain the biological processes that are operating in the lake to produce the observed data. Explain also how these processes would account for your prediction of results for a heavily overcast day.Describe how the introduction of high levels of nutrients such as nitrates and phosphates into the lake would affect subsequent observations. Explain your predictions.hour6am8am10amnoon2pm4pm6pm8pm10pmmid[O2] mg/L0.91.73.14.126.96.36.199.24.02.4
11 Lab 12: Dissolved Oxygen ESSAY 2004B In most aquatic environments, primary production is affected by light available to the community of organisms.Using measurements of dissolved oxygen concentration to determine primary productivity, design a controlled experiment to test the hypothesis that primary productivity is affected by either the intensity of light or the wavelength of light. In your answer, be sure to include the following.A statement of the specific hypothesis that you are testingA description of your experimental design (Be sure to include a description of what data you would collect and how you would present and analyze the data using a graph.)A description of results that would support your hypothesis
12 Eutrophication A nutrient overload causes an algal bloom Algal bloom Thick layer of algae growth at surface of waterBlocks sunlight from penetrating lower levels of water body
14 How are algal blooms harmful? Algae blocks out sunPlants don’t photosynthesizeOxygen decreasesCO2 increasesKills fish!Anoxia: "without oxygen”Hypoxia: "low oxygen"
15 excess nutrients streams & ponds Feeds algae in water, causes rapid growth (bloom)When the algae die, saprophytes utilize oxygen in water during decompositionOther organisms die due to low oxygen levels more decompositionLake becomes shallow, build up of organic material at bottom of lake