AP Lab #12  Dissolved Oxygen & Aquatic Primary Productivity
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AP Lab #12 Dissolved Oxygen & Aquatic Primary Productivity part I. In an aquatic environment, O 2 must be in a solution in a free state before it is available for use by heterotrophic organisms….

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

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Ap lab 12 dissolved oxygen aquatic primary productivity part i

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


Ap lab 12 dissolved oxygen aquatic primary productivity part i

In an aquatic environment, O2must be in a solution in a free state before it is available for use by heterotrophic organisms…


Ap lab 12 dissolved oxygen aquatic primary productivity part i

In an aquatic environment, O2 must be in a solution in a free state before it is available for use by heterotrophic organisms…

The concentration of O2, 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 … O2 is abundant


Ap lab 12 dissolved oxygen aquatic primary productivity part i

Terrestrial = 200 mL O2/ 1 L air

Aquatic = 10 mL O2/ 1 L water

WHY???

In an aquatic environmentO2 is NOT as abundant as in a terrestrial…


Ap lab 12 dissolved oxygen aquatic primary productivity part i

Terrestrial = 200 mL O2/ 1 L air

Aquatic = 10 mL O2/ 1 L water

O2distribution in water depends on: currents, winds, tides etc. mixing it up !

O2 diffuses 300,000 X’s fasterinair than water


Ap lab 12 dissolved oxygen aquatic primary productivity part i

Terrestrial = 200 mL O2/ 1 L air

Aquatic = 10 mL O2/ 1 L water

O2 distribution in water also depends on: pH,


Ap lab 12 dissolved oxygen aquatic primary productivity part i

Terrestrial = 200 mL O2/ 1 L air

Aquatic = 10 mL O2/ 1 L water

O2 distribution in water also depends on: salinity,


Ap lab 12 dissolved oxygen aquatic primary productivity part i

Terrestrial = 200 mL O2/ 1 L air

Aquatic = 10 mL O2/ 1 L water

O2 distribution in water also depends on: elevation


Ap lab 12 dissolved oxygen aquatic primary productivity part i

Terrestrial = 200 mL O2/ 1 L air

Aquatic = 10 mL O2/ 1 L water

O2 distribution in water also depends on: temperature


Ap lab 12 dissolved oxygen aquatic primary productivity part i

HIGHER O2 (DO) CONCENTRATION (ppm) at:

“Help - I am suffocating!!!”

neutral pH

low elevation

low salinity

low temperature


Ap lab 12 dissolved oxygen aquatic primary productivity part i

Terrestrial = 200 mL O2/ 1 L air

Aquatic = 10 mL O2/ 1 L water

O2 distribution in water also depends on: partial pressure of O2 in the air above the water !


Ap lab 12 dissolved oxygen aquatic primary productivity part i

LESS O2 IN WATER AT HIGHER ELEVATIONS

THAN AT LOWER ELEVATIONS


Ap lab 12 dissolved oxygen aquatic primary productivity part i

You could think about the amount of O2 in the air @ these locations…


Ap lab 12 dissolved oxygen aquatic primary productivity part i

Terrestrial = 200 mL O2/ 1 L air

Aquatic = 10 mL O2/ 1 L water

O2 distribution in water also depends on: amount (rate) of photosynthesis & respiration


Ap lab 12 dissolved oxygen aquatic primary productivity part i

photosynthesis increases the D.O. (ppm) !

respiration decreases the D.O.(ppm) …


Ap lab 12 dissolved oxygen aquatic primary productivity part i

measuring D.O. is a determiner as to whether the biological activities requiring O2 are occurring (respiration)

Indicator of health of lake !


Which environment has the greater concentration of dissolved oxygen explain

Which environment has the greater concentration of dissolved oxygen: Explain.

or a clear pond?

a heavy algal mat?


Ap lab 12 dissolved oxygen aquatic primary productivity part i

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.


Say what

??? SAY WHAT????


Ap lab 12 dissolved oxygen aquatic primary productivity part i

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


Ap lab 12 dissolved oxygen aquatic primary productivity part i

Just HOW do you measure D.O.?

Winkler

method


Ap lab 12 dissolved oxygen aquatic primary productivity part i

Just HOW do you measure D.O.?

via.

titration


Ap lab 12 dissolved oxygen aquatic primary productivity part i

WINKLER METHOD to determine D.O.

1. Add alkaline iodide & manganous sulfateto a water sample.

Manganous hydroxide will be produced.

This will be acidified, & will spontaneously be converted to a manganese compound by the O2 in the water sample


Ap lab 12 dissolved oxygen aquatic primary productivity part i

WINKLER METHOD to determine D.O.

2. Add alkaline potassium iodide azide (KOH)to the water sample.

Iodine will be released -> H2O will turn yellow

**The quantity of free iodine is equivalent to the amount of D.O. in the water.**


Ap lab 12 dissolved oxygen aquatic primary productivity part i

WINKLER METHOD to determine D.O.

3. A starch indicator is then added… to determine amount of iodine via. titration

H2O 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.


Ap lab 12 dissolved oxygen aquatic primary productivity part i

WINKLER METHOD to determine D.O.

4. The amount of D.O. can then be determined by titrating aportion of the sample with sodium thiosulfate until a colorless endpoint is reached.


Ap lab 12 dissolved oxygen aquatic primary productivity part i

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


Ap lab 12 dissolved oxygen aquatic primary productivity part i

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:


Ap lab 12 dissolved oxygen aquatic primary productivity part i

the percent oxygen saturation for a water sample at 10oC that has 7mg O2/L is 45% saturation

nomograph


Ap lab 12 dissolved oxygen aquatic primary productivity part i

the percent oxygen saturation for a water sample at 25oC that has 7mg O2/L is 65% saturation

nomograph


Ap lab 12 dissolved oxygen aquatic primary productivity part i

Day 1

temp. effect

4 degrees C

25 degrees C

30 degrees C

Goggles and gloves MUST be worn


Ap lab 12 dissolved oxygen aquatic primary productivity part i

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


Ap lab 12 dissolved oxygen aquatic primary productivity part i

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


Ap lab 12 dissolved oxygen aquatic primary productivity part i

Primary Productivity

the rate @ which biomass is produced & stored (by autotrophs) via. photosynthesis in an ecosystem


Ap lab 12 dissolved oxygen aquatic primary productivity part i

Primary Productivity

amount of organic compound formed from photosynthesis

amount of organic compound used by respiration

-

Aquatic P.P.


Ap lab 12 dissolved oxygen aquatic primary productivity part i

Primary Productivity

amount of organic compound formed from photosynthesis

-

amount of organic compound used by respiration

Net Primary Production


Ap lab 12 dissolved oxygen aquatic primary productivity part i

Primary Productivity can be measured by:

*rate of CO2 utilization

*rate of sugar formation

(glucose produced)

*rate of O2 production in the light


Ap lab 12 dissolved oxygen aquatic primary productivity part i

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


Ap lab 12 dissolved oxygen aquatic primary productivity part i

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


Ap lab 12 dissolved oxygen aquatic primary productivity part i

Just HOW do you measure primary productivity?

Light-Dark

bottle O2

method


Ap lab 12 dissolved oxygen aquatic primary productivity part i

Light-Dark bottleO2method 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


Ap lab 12 dissolved oxygen aquatic primary productivity part i

Light-Dark bottleO2method to determine primary productivity

RESPIRATION -> initial sample - dark sample

GROSSPRIMARYPRODUCTION -> light sample+ amount used in dark sample

NETPRIMARYPRODUCTION -> light sample- dark sample


Ap lab 12 dissolved oxygen aquatic primary productivity part i

Day 2

primary

productivity


Ap lab 12 dissolved oxygen aquatic primary productivity part i

Day 2

primary

productivity


Ap lab 12 dissolved oxygen aquatic primary productivity part i

Day 2

primary

productivity

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


Ap lab 12 dissolved oxygen aquatic primary productivity part i

Day 2

primary

productivity

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


Ap lab 12 dissolved oxygen aquatic primary productivity part i

Day 2

primary

productivity

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


Ap lab 12 dissolved oxygen aquatic primary productivity part i

Day 2

primary

productivity


Ap lab 12 dissolved oxygen aquatic primary productivity part i

L - I = Net Productivity

I - D = Respiration

L - D = Gross Productivity

note: dark is a negative number

L

DO (mL O2 / L)

Net Productivity

I

Gross Productivity

Respiration

I = Initial Bottle L = Light Bottle D = Dark Bottle

D

Incubation Time (hours)

24

0


Ap lab 12 dissolved oxygen aquatic primary productivity part i

net productivity + respiration = gross productivity

(light - initial) + (initial - dark) = gross productivity

(light) + (- dark) = gross productivity

light - dark = gross productivity

you subtract

to get gross

b/c:


Ap lab 12 dissolved oxygen aquatic primary productivity part i

this number will be negative


Ap lab 12 dissolved oxygen aquatic primary productivity part i

this number will be negative


How do lakes age

How do lakes age?


Oligotrophic

OLIGOTROPHIC


Oligotrophic1

OLIGOTROPHIC

  • Very little nutrients (nitrogen & phosphorus

  • Deep

  • Clear

  • Very little algae

  • Colder

  • Highly oxygenated


Ap lab 12 dissolved oxygen aquatic primary productivity part i

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.


Mesotrophic

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


Eutrophic

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


Ap lab 12 dissolved oxygen aquatic primary productivity part i

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.


Ap lab 12 dissolved oxygen aquatic primary productivity part i

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.


Ap lab 12 dissolved oxygen aquatic primary productivity part i

A eutrophic lake


Ap lab 12 dissolved oxygen aquatic primary productivity part i

  • A eutrophic lake is shallow with high nutrient content.

  • 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.


Ap lab 12 dissolved oxygen aquatic primary productivity part i

A eutrophic lake


Ap lab 12 dissolved oxygen aquatic primary productivity part i

A oligotrophic lake


Ap lab 12 dissolved oxygen aquatic primary productivity part i

SPRING TURNOVER


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