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

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

In an aquatic environment, In an aquatic environment, OO22 must must be in a solution in a free state be in a solution in a free state before it is available for use by before it is available for use by heterotrophic organisms…heterotrophic organisms…

In an aquatic environment, In an aquatic environment, OO22 must must be in a solution in a free state be in a solution in a free state before it is available for use by before it is available for use by heterotrophic organisms…heterotrophic organisms…The concentration of OThe concentration of O22, and its , and its

distribution in an aquatic distribution in an aquatic environment (the pond, ocean environment (the pond, ocean

etc.), are directly dependent on etc.), are directly dependent on factors that greatly affected by factors that greatly affected by

biological processes!biological processes!In the In the atmosphereatmosphere …… O O22 is is abundantabundant

Terrestrial = 200 mL OTerrestrial = 200 mL O22/ 1 / 1 L airL air

In an aquatic In an aquatic environmentenvironment OO22 is is NOT as abundant NOT as abundant as in a terrestrial…as in a terrestrial…

Aquatic = 10 mL OAquatic = 10 mL O22/ 1 / 1 L L waterwater

Terrestrial = 200 mL OTerrestrial = 200 mL O22/ 1 / 1 L airL air

OO2 2 diffuses 300,000 diffuses 300,000 X’s X’s fasterfaster inin airair than than waterwater

Aquatic = 10 mL OAquatic = 10 mL O22/ 1 / 1 L L waterwaterOO22 distributiondistribution in in water depends on: water depends on: currents, winds, currents, winds, tides etc. mixing it tides etc. mixing it up up !!

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Terrestrial = 200 mL OTerrestrial = 200 mL O22/ 1 / 1 L airL airAquatic = 10 mL OAquatic = 10 mL O22/ 1 / 1 L L waterwaterOO22 distribution in distribution in water water alsoalso depends depends on: on: pH, pH,

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Terrestrial = 200 mL OTerrestrial = 200 mL O22/ 1 / 1 L airL airAquatic = 10 mL OAquatic = 10 mL O22/ 1 / 1 L L waterwaterOO22 distribution in distribution in water water alsoalso depends depends on: on: salinity,salinity,

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Terrestrial = 200 mL OTerrestrial = 200 mL O22/ 1 / 1 L airL airAquatic = 10 mL OAquatic = 10 mL O22/ 1 / 1 L L waterwaterOO22 distribution in distribution in water water alsoalso depends depends on: on: elevation elevation

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Terrestrial = 200 mL OTerrestrial = 200 mL O22/ 1 / 1 L airL airAquatic = 10 mL OAquatic = 10 mL O22/ 1 / 1 L L waterwaterOO22 distribution in distribution in water water alsoalso depends depends on: on: temperaturetemperature

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HIGHER OHIGHER O22 (DO) (DO) CONCENTRATION CONCENTRATION (ppm) at:(ppm) at:

“Help - I am suffocating!!!”

neutral pHneutral pH

low low temperaturetemperature

low elevationlow elevationlow salinitylow salinity

Terrestrial = 200 mL OTerrestrial = 200 mL O22/ 1 / 1 L airL airAquatic = 10 mL OAquatic = 10 mL O22/ 1 / 1 L L waterwaterOO22 distribution in distribution in water water alsoalso depends depends on: on: partial pressure partial pressure of Oof O22 in the air in the air above the water above the water !!

LESS OLESS O22 IN WATER IN WATER AT HIGHER AT HIGHER

ELEVATIONSELEVATIONS

THAN AT THAN AT LOWER LOWER

ELEVATIONSELEVATIONS

You could You could think about think about the amount of the amount of OO22 in the air in the air @ these @ these locations…locations…

Terrestrial = 200 mL OTerrestrial = 200 mL O22/ 1 / 1 L airL airAquatic = 10 mL OAquatic = 10 mL O22/ 1 / 1 L L waterwaterOO22 distribution in distribution in water water alsoalso depends depends on: on: amount (rate) of amount (rate) of photosynthesis & photosynthesis &

respirationrespiration

photosynthesis photosynthesis increases the D.O. increases the D.O. (ppm) (ppm) !!

respiration decreases respiration decreases the D.O.(ppm) …the D.O.(ppm) …

measuring D.O. is a measuring D.O. is a determiner as to determiner as to

whether the whether the biological activities biological activities

requiringrequiring O O22 are are occurringoccurring

(respiration)(respiration)Indicator of health of Indicator of health of

lake lake ! !

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

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a heavy algal mat?a heavy algal mat? or a clear pond?or a clear pond?

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

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??? SAY WHAT??????? SAY WHAT????

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

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Just Just HOW do HOW do

you you measure measure

D.O.?D.O.?

Just Just HOW do HOW do

you you measure measure

D.O.?D.O.?

WINKLER METHOD

to determine D.O.

1. Add 1. Add alkaline iodide & manganous alkaline iodide & manganous sulfatesulfate to a water sample.to a water sample.

Manganous hydroxideManganous hydroxide will be produced. will be produced.

This will be acidified, & will spontaneously This will be acidified, & will spontaneously be converted to a be converted to a manganese compoundmanganese compound by by

the the OO22 in the water sample in the water sample

WINKLER METHOD to determine D.O.

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

IodineIodine will be released -> will be released -> HH22O will turn O will turn

yellow yellow**The quantity of **The quantity of free iodinefree iodine is is

equivalent to the amount of equivalent to the amount of D.O.D.O. in the in the water.**water.**

WINKLER METHOD to determine D.O.

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

via. via. titrationtitration

HH22O will turn purpleO will turn purple

You remember, titration is adding a substance of known You remember, titration is adding a substance of known concentration to a solution containing a substance of unknown concentration to a solution containing a substance of unknown

concentration… until a specific reactions completed and a color concentration… until a specific reactions completed and a color change occurs.change occurs.

WINKLER METHOD to determine D.O.

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

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

MEASURING D.O.

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

nomograph

the percent the percent oxygen oxygen

saturation for a saturation for a water sample at water sample at

1010ooC that has C that has 7mg O7mg O22/L is 45% /L is 45%

saturationsaturation

nomograph

the percent the percent oxygen oxygen

saturation for a saturation for a water sample at water sample at

2525ooC that has C that has 7mg O7mg O22/L is 65% /L is 65%

saturationsaturation

Goggles and gloves MUST be worn

AP Lab #12 AP Lab #12 Dissolved Oxygen & Dissolved Oxygen &

Aquatic Primary Aquatic Primary Productivity Day 2Productivity Day 2

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

lightlight

Primary ProductivityPrimary Productivitythe rate @ which biomass the rate @ which biomass is produced & stored is produced & stored (by (by

autotrophs)autotrophs) via. via. photosynthesis in an photosynthesis in an

ecosystemecosystem

Primary ProductivityPrimary Productivity

amount of organic amount of organic compound formed compound formed

from photosynthesisfrom photosynthesis-- amount of organic amount of organic compound used by compound used by

respirationrespirationAquatic P.P.Aquatic P.P.

Primary ProductivityPrimary Productivity

amount of organic compound amount of organic compound formed from photosynthesisformed from photosynthesis--amount of organic compound amount of organic compound used by respirationused by respiration

Net Primary Net Primary ProductionProduction

Primary Productivity Primary Productivity can be measured can be measured

by:by:*rate of CO*rate of CO22 utilizationutilization*rate of sugar *rate of sugar formation formation (glucose produced)(glucose produced)*rate of O*rate of O22 production in production in the lightthe light

Primary Productivity Primary Productivity can be measured can be measured

by:by:can calculate the can calculate the amount of carbon that amount of carbon that has been “bound” in has been “bound” in organic compounds organic compounds over a timeover a time via. RATE OF Ovia. RATE OF O22 PRODUCTIONPRODUCTION

You will You will monitor the monitor the

effect of effect of varying light varying light

levels on D.O. levels on D.O. in an algae- in an algae-

rich water rich water cultureculture

Just HOW Just HOW do you do you

measure measure primary primary

productiviproductivity?ty?

Light-Dark bottle

O2method to determine primary

productivity1. Measure D.O. concentration in an 1. Measure D.O. concentration in an initial sample initial sample CONTROL TO COMPARECONTROL TO COMPARE

2. 2. Measure D.O. concentration in a Measure D.O. concentration in a dark sample JUST CELL RESPIRATIONdark sample JUST CELL RESPIRATION

3. 3. Measure D.O. concentration in a Measure D.O. concentration in a light sample PHOTOSYNTHESIS & light sample PHOTOSYNTHESIS &

CELL RESPIRATION CELL RESPIRATION

Light-Dark bottle

O2method to determine primary

productivityRESPIRATIONRESPIRATION -> -> initial sample - dark sampleinitial sample - dark sample

GROSSGROSS PRIMARYPRIMARY PRODUCTIONPRODUCTION -> -> light samplelight sample + amount used in dark sample+ amount used in dark sample

NETNET PRIMARYPRIMARY PRODUCTIONPRODUCTION -> -> light samplelight sample - dark sample- dark sample

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

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

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

DO

(m

L 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

net productivity + respiration = gross productivity

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

(light) + (- dark) = gross productivity

light - dark = gross productivity

this number will be negative

this number will be negative

How do lakes age?

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OLIGOTROPHIC

OLIGOTROPHIC

• Very little nutrients (nitrogen & phosphorus

• Deep• Clear• Very little algae• Colder• Highly oxygenated

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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• 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

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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

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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.

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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.

A eutrophic lake

A eutrophic lake is shallow with high nutrient content. •The phytoplankton are very productive and The phytoplankton are very productive and

the waters are often murky. the waters are often murky.

•Ecologist use the term to describe Ecologist use the term to describe relatively relatively productive habitatsproductive habitats and communities having and communities having

good nutrient supply and to separate them good nutrient supply and to separate them from unproductive from unproductive oligotrophicoligotrophic ones, ones, characterized by a nutrient deficiency.characterized by a nutrient deficiency.

A eutrophic lake

A oligotrophic lake

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SPRING TURNOVER