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AP Lab #12 Dissolved Oxygen & Aquatic Primary Productivity part I.

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Presentation on theme: "AP Lab #12 Dissolved Oxygen & Aquatic Primary Productivity part I."— Presentation transcript:

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2 AP Lab #12 Dissolved Oxygen & Aquatic Primary Productivity part I

3 In an aquatic environment, O 2 must be in a solution in a free state before it is available for use by heterotrophic organisms…

4 The concentration of O 2, and its distribution in an aquatic environment (the pond, ocean etc.), are directly dependent on factors that greatly affected by biological processes! In the atmosphere … O 2 is abundant

5 Terrestrial = 200 mL O 2 / 1 L air In an aquatic environmentO 2 is NOT as abundant as in a terrestrial… Aquatic = 10 mL O 2 / 1 L water

6 Terrestrial = 200 mL O 2 / 1 L air O 2 diffuses 300,000 X’s faster in air than water Aquatic = 10 mL O 2 / 1 L water O 2 distribution in water depends on: currents, winds, tides etc. mixing it up !

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8 Terrestrial = 200 mL O 2 / 1 L air Aquatic = 10 mL O 2 / 1 L water O 2 distribution in water also depends on: pH,

9 Terrestrial = 200 mL O 2 / 1 L air Aquatic = 10 mL O 2 / 1 L water O 2 distribution in water also depends on: salinity,

10 Terrestrial = 200 mL O 2 / 1 L air Aquatic = 10 mL O 2 / 1 L water O 2 distribution in water also depends on: elevation

11 Terrestrial = 200 mL O 2 / 1 L air Aquatic = 10 mL O 2 / 1 L water O 2 distribution in water also depends on: temperature

12 HIGHER O 2 (DO) CONCENTRATION (ppm) at: “Help - I am suffocating!!!” neutral pH low temperature low elevation low salinity

13 Terrestrial = 200 mL O 2 / 1 L air Aquatic = 10 mL O 2 / 1 L water O 2 distribution in water also depends on: partial pressure of O 2 in the air above the water !

14 LESS O 2 IN WATER AT HIGHER ELEVATIONS THAN AT LOWER ELEVATIONS

15 You could think about the amount of O 2 in the these locations…

16 Terrestrial = 200 mL O 2 / 1 L air Aquatic = 10 mL O 2 / 1 L water O 2 distribution in water also depends on: amount (rate) of photosynthesis & respiration

17 photosynthesis increases the D.O. (ppm) ! respiration decreases the D.O.(ppm) …

18 measuring D.O. is a determiner as to whether the biological activities requiring O 2 are occurring (respiration) Indicator of health of lake !

19 Which environment has the greater concentration of dissolved oxygen: Explain. a heavy algal mat? or a clear pond?

20 Clear water holds more dissolved oxygen than water with a heavy algal mat. Although photosynthesis in the algal mat will produce a great deal of oxygen, the decay of so much organic matter will result in a net depletion of oxygen due to DECOMPOSERS.

21 ??? SAY WHAT????

22 DECOMPOSERS w/ be in a large amount BECAUSE THE ALGAE WILL EVENTUALLY DIE... The decomposers w/ come on the scene and will USE THE OXYGEN, thus decreasing the amount of DO

23 Just HOW do you measure D.O.?

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25 WINKLER METHOD to determine D.O. 1. Add alkaline iodide & manganous sulfate to a water sample. Manganous hydroxide will be produced. This will be acidified, & will spontaneously be converted to a manganese compound by the O 2 in the water sample

26 WINKLER METHOD to determine D.O. 2. Add alkaline potassium iodide azide (KOH) to the water sample. Iodine will be released -> H 2 O will turn yellow **The quantity of free iodine is equivalent to the amount of D.O. in the water.**

27 WINKLER METHOD to determine D.O. 3. A starch indicator is then added… to determine amount of iodine via. titration H 2 O will turn purple You remember, titration is adding a substance of known concentration to a solution containing a substance of unknown concentration… until a specific reactions completed and a color change occurs.

28 WINKLER METHOD to determine D.O. 4. The amount of D.O. can then be determined by titrating a portion of the sample with sodium thiosulfate until a colorless endpoint is reached.

29 AP Lab #12 Dissolved Oxygen & Aquatic Primary Productivity part I

30 MEASURING D.O. In order to measure how much oxygen water can hold (the saturation) you will also need to be able to read a nomograph:

31 nomograph the percent oxygen saturation for a water sample at 10 o C 10 o C that has 7mg O 2 /L O 2 /L is 45% saturation

32 nomograph the percent oxygen saturation for a water sample at 25 o C 25 o C that has 7mg O 2 /L O 2 /L is 65% saturation

33 Goggles and gloves MUST be worn

34 AP Lab #12 Dissolved Oxygen & Aquatic Primary Productivity Day 2

35 Day 2 we will compare D.O. values in water samples exposed to differing amounts of light

36 Primary Productivity the which biomass is produced & stored (by autotrophs) via. photosynthesis in an ecosystem

37 Primary Productivity amount of organic compound formed from photosynthesis - amount of organic compound used by respiration Aquatic P.P.

38 Primary Productivity amount of organic compound formed from photosynthesis - amount of organic compound used by respiration Net Primary Production

39 Primary Productivity can be measured by: *rate of CO 2 utilization *rate of sugar formation (glucose produced) (glucose produced) *rate of O 2 production in the light

40 Primary Productivity can be measured by: can calculate the amount of carbon that has been “bound” in organic compounds over a time via. RATE OF O2 PRODUCTION

41 You will monitor the effect of varying light levels on D.O. in an algae-rich water culture

42 Just HOW do you measure primary productivity ?

43 Light-Dark bottle O 2 method to determine primary productivity 1. Measure D.O. concentration in an initial sample CONTROL TO COMPARE 2. Measure D.O. concentration in a dark sample JUST CELL RESPIRATION 3. Measure D.O. concentration in a light sample PHOTOSYNTHESIS & CELL RESPIRATION

44 Light-Dark bottle O 2 method to determine primary productivity RESPIRATION -> initial sample - dark sample GROSS PRIMARY PRODUCTION -> light sample + amount used in dark sample NET PRIMARY PRODUCTION -> light sample - dark sample

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47 3. Each bottle will have the % light it will receive..

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52 DO (mL O 2 / L) Incubation Time (hours) 0 24 L I D Gross Productivity L - I = Net Productivity I - D = Respiration L - D = Gross Productivity note: dark is a negative number I = Initial Bottle L = Light Bottle D = Dark Bottle Net Productivity Respiration

53 net productivity + respiration = gross productivity (light - initial) + (initial - dark) = gross productivity (light) + (- dark) = gross productivity light - dark = gross productivity

54 this number will be negative

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58 How do lakes age?

59 OLIGOTROPHIC

60 Very little nutrients (nitrogen & phosphorus Deep Clear Very little algae Colder Highly oxygenated

61 A oligotrophic lake Oligotrophic lakes are very low in nutrients, so few algae grow and the water is very clear. Oligotrophic lakes are biologically less productive lakes (they have the lowest level of biological productivity), and support very few plants and fish.

62 MESOTROPHIC Medium amount of nutrients (nitrogen & phosphorus) Clear Algal blooms in late summer on top~ D.O. higher on top Warm on top /Colder on bottom Higher decomposition rate on bottom~ D.O. lower on bottom

63 EUTROPHIC High amount of nutrients (nitrogen & phosphorus) Shallow/ Murkey Algal blooms b/c of nutrients / high fish Higher decomposition rate on bottom~ D.O. lower all over

64 EUTROPHICATION a natural process that occurs in an aging lake or pond as that body of water gradually builds up its concentration of plant nutrients.

65 EUTROPHICATION Cultural or artificial eutrophication occurs when human activity introduces increased amounts of these nutrients, which speed up plant growth and eventually choke the lake of all of its animal life.

66 A eutrophic lake

67 A eutrophic lake is shallow with high nutrient content. The phytoplankton are very productive and the waters are often murky.The phytoplankton are very productive and the waters are often murky. Ecologist use the term to describe relatively productive habitats and communities having good nutrient supply and to separate them from unproductive oligotrophic ones, characterized by a nutrient deficiency.Ecologist use the term to describe relatively productive habitats and communities having good nutrient supply and to separate them from unproductive oligotrophic ones, characterized by a nutrient deficiency.

68 A eutrophic lake

69 A oligotrophic lake

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71 SPRING TURNOVER


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