Dissolved Oxygen and Aquatic Primary Productivity
AP Biology
AP Lab 12--DISSOLVED OXYGEN & AQUATIC PRIMARY PRODUCTIVITY (LabBench)
Web address: http://www.phschool.com/science/biology_place/labbench
Click on Lab 12: Dissolved Oxygen & Aquatic Primary Productivity
A. KEY CONCEPTS:
1. Dissolved Oxygen Availability in ponds and lakes. Using the following diagram describe the effect that each of the factors has on availability of oxygen and explain why.
a.
Temperature: The warmer the water, the the shorter the amount of oxygen is present.
b.
Light & Photosynthesis: Clear sunlight from the sun is able to produce more oxygen.
c.
Decomposition & Respiration: The process of decomposition requires oxygen to run.
d.
Mixing & Turbulence : The concentration of the oxygen is strengthened
e.
Salinity :The saltier the water, the lesser amount of oxygen it is able to hold.
2. Productivity: Define each of these terms in your own words.
a.
Primary productivity: The rate of production of organic compounds from photosynthetic organisms.
b.
Gross productivity: All the production results in the ecosystem.
c.
Net productivity: Resulting amount of the organic compounds in the end after some of it has been used.
_
3.
Why do we use dissolved oxygen as a measure of productivity? Does productivity include more than oxygen?
We use dissolved oxygen because it is easy to use in both photosynthesis and respiration. Yes, productivity also includes organic compounds.
4.
Using the diagrams below explain:
a.
How does putting a sample of pond water and algae/freshwater plants in the light enable us to measure gross productivity?
It enables us to show which is able to produce more products.
b.
How does putting a sample of pond water and algae/freshwater plants in the dark enable us to measure respiration?
It enables us to see which of the two uses up more oxygen.
c.
How does subtracting the two enable us to indirectly measure net productivity?
Net productivity are the results of oxygen being produced and taken in, so this enables us to measure the ending results.
5.
What are the three ways that primary productivity can be measured? Highlight the way will be used in this lab?.
a.
Measuring during photosynthesis
b.
Measuring during respiration when two O2 is being consumed.
c.
Subtracting gross productivity and respiration.
LAB PART 1: EFFECT OF TEMPERATURE ON DISSOLVED OXYGEN
We actually did this part of the lab already. Remind yourself of our experiment, our procedures, and our conclusions. We were investigating the effect of the physical factor of temperature on the percent dissolved oxygen in a body of water.
6.
What is the relationship between water temperature and dissolved oxygen?
- Warmer waters equals a more less amount of dissolved oxygen
7.
Explain why this relationship exists.
-Molecules in higher temperatures move a lot quicker making dissolved oxygen not being able to stay.
8.
So, now explain why the fish in the aquarium (on the LabBench Web site) above the radiator died?
-The fish drowned in water with no oxygen
A MODEL OF PRODUCTIVITY AS A FUNCTION OF DEPTH IN A LAKE
Now we are going to look at the biological factors that affect dissolved oxygen in a body of water. Look at the experimental design on the LabBench Web site (http://www.phschool.com/science/biology_place/labbench/lab12/model.html). We are taking a sample of pond water (with algae) and then modeling different depths in the pond by using screening to block out successive amounts of light. One hundred percent light for shallow depth, all the way to 0% light for deep ponds.
9.
Why do we take an initial reading of dissolved oxygen? What purpose does this serve in the experiment?
-Initial readings are used to check for change in the results
10.
Click on the “closer look” magnifying glass on the “initial bottle”. Why does the animation show oxygen being diffusing out of the freshwater plants? What does this signify?
- The oxygen shows the production of new air, this signifies photosynthesis
11. Click on the “closer look” magnifying glass on the foil- covered bottle. Why does the animation show oxygen diffusing into the freshwater plants? What does this signify?- The oxygen is being sucked into the plants. This shows respiration
12.
Click on the “closer look” magnifying glass on the 100% bottle under the light. Why does the animation show oxygen diffusing both into and out of the freshwater plants? What does this signify?
- This one also shows the production of new air. This signifies photosynthesis
ANALYSIS OF RESULTS
Let’s look at the results that will allow you to calculate the different types of productivity.
13. Measuring Respiration: Remember that plants (producers) perform both photosynthesis and respiration. To measure the amount of respiration that is happening in the bottle, we measure the amount of dissolved oxygen in the initial sample and then the amount of oxygen in the bottle kept in the dark. As shown in the illustration below, you then subtract the amount of dissolved oxygen in the “dark bottle” from the amount of dissolved oxygen in the “initial bottle” to calculate the amount of oxygen consumed in respiration. I have added some possible measurements to help. Explain why this calculation works.
- Because the initial bottle had more and the dark bottle ended up having less, this shows the net productivity of resulting in having less of the original since the plant absorbed the oxygen in the darkness.
14. Measuring Gross Productivity: Remember gross productivity is the total amount of sugars and oxygen produced by the plants in an ecosystem. I don’t like how this Web site shows you how to calculate gross productivity. The equation is correct, but it is a shortcut, so it makes it more difficult to understand. So follow me with the illustrations and the possible measurements below.
So the illustration shows us there was 10mg increase in dissolved oxygen in the jar as a result of photosynthesis in the last 24 hours and there was 5mg decrease in dissolved oxygen in the jar as a result of respiration in the last 24 hours. So the gross productivity (the full photosynthetic production in this ecosystem) of the algae in the bottle is the 5mg dissolved oxygen lost to respiration added back to the 10 mg dissolved oxygen accumulated in the bottle kept in the light. So what the algae really produced in the bottle was a total of 15mg dissolved oxygen, it just lost 5mg to respiration. And remember, the oxygen is an indirect measurement of the sugars produced in photosynthesis and lost in respiration.
10 mg oxygen gained
5 mg oxygen lost
15 mg oxygen as
+
=
from photosynthesis
to respiration
gross productivity
Now, in your own words, explain why this calculation works.
-Gross productivity, are the resulting products of all the losses and gains. Because the bottles gained 10 mg and lost 5 mg, the word of gross productivity being placed at the end shows that all productivity had a 15 mg amount altogether.
15. Measuring Net Productivity: Remember net productivity is the amount of sugars and dissolved oxygen produced by the plants in an ecosystem once you subtract out what the producers have consumed in respiration. So we actually already calculated that in the last example; I just called it “net photosynthesis.” Explain why this calculation works.
- The ending result of the lab shows the work of photosynthesis. Because the initial bottle started with less, the difference between the two show how much of a difference the resulted bottle ended with.
16.
Print out the completed calculation table from Sample Problem page of the LabBench Web site, fill in your predictions on the graph as well, and attach it to this lab to show me that you have completed it.
(Below)
17.
Print out the Lab Quiz and attach it to this lab to show me that you completed it.
SUMMARY QUESTIONS
(Below)
18.
Would you expect the dissolved oxygen levels in water sampled from a stream entering a lake to be higher or lower than the dissolved oxygen levels in water sampled from the lake itself? Explain.-I expect it to be higher as the stream entering the lake started at a higher point making the air more colder than at the lake.
19.
Would you expect the dissolved oxygen levels in water sampled from a lake at 7AM to be higher or lower than the dissolved oxygen levels in water sampled at 5PM? Explain.
- I would expect it to be higher as the sun has not risen high enough yet making the air more colder than in the after noon.
20.
One of the major sources of water pollution is the runoff from fertilizer used in agriculture and on suburban lawns as well as golf courses. In particular, the nitrogen and phosphorus nutrients in the fertilizer creates problems in the streams and ponds it flows into. They cause algal blooms and eutrophication in lakes.
a.
Why do nitrogen and phosphorus promote a lot of plant/algal growth?
- These minerals are considered food to the plants making them produce more.
b.
What is meant by algal bloom? (Look it up!)
- Algal bloom is the over population of the algae due to the overfeeding of the nutrients.
c.
What problems do algal blooms cause in ponds & lakes? Why isn’t a lot more producers a good thing? (Look it up!)
- Algal blooms end up covering the sunlight from reaching the depths of the water making it harder to synthesize.
d.
What is meant by eutrophication? (Look it up!)
- An excessive release of nutrients into lakes and ponds.
21.
At what depth—shallow or deep—will there be more primary productivity in a pond or a lake? Explain.
- More primary productivity will be in the shallow zone and sunlight is easier to reach.
22.
In an experiment, why do we use the mean of class data to make conclusions rather than individual student group data?
- We use class data to make conclusions because we can see a more broad set of data to average between.
23.
AP exam FRQ (2008). Consumers in aquatic ecosystems depend on producers for nutrition.
a.
Explain the difference between gross and net primary productivity.
-Gross productivity are the results of all losses and gains. Net productivity shows the difference between the initial and the resulting products.
b.
Describe a method to determine net and gross primary productivity in a freshwater pond over a 24-hour period.
- Net productivity: Record the data of the initial amount of organic compounds then record the data for the resulting amount. Subtract the two.
-Gross productivity: Add the amount of losses and gains of the resulting product.
c.
In an experiment, net primary productivity was measured, in the early spring, for water samples taken from different depths of a freshwater pond in a temperate deciduous forest.
Explain the data presented by the graph, including a description of the relative rates of metabolic processes occurring at different depths of the pond.
- The line on the graph shows the changing net productivity as the depth of the water increases. The line seems to be at its highest on the lowest water depth and gradually getting smaller in numbers the higher the depth of the water. At about thirty the net productivity ends up having a lower rate than the original number.
d.
Describe how the relationship between net primary productivity and depth would be expected to differ if new data were collected in mid-summer from the same pond. Explain your prediction.
- The net primary productivity would be a lot more higher. Though the deeper the water, the lower it would be , the numbers will still be higher than how it was back then. Because the sunlight is more closer to the water, more net productivity would be produced.
AP Lab 12--DISSOLVED OXYGEN & AQUATIC PRIMARY PRODUCTIVITY (LabBench)
Web address: http://www.phschool.com/science/biology_place/labbench
Click on Lab 12: Dissolved Oxygen & Aquatic Primary Productivity
A. KEY CONCEPTS:
1. Dissolved Oxygen Availability in ponds and lakes. Using the following diagram describe the effect that each of the factors has on availability of oxygen and explain why.
a.
Temperature: The warmer the water, the the shorter the amount of oxygen is present.
b.
Light & Photosynthesis: Clear sunlight from the sun is able to produce more oxygen.
c.
Decomposition & Respiration: The process of decomposition requires oxygen to run.
d.
Mixing & Turbulence : The concentration of the oxygen is strengthened
e.
Salinity :The saltier the water, the lesser amount of oxygen it is able to hold.
2. Productivity: Define each of these terms in your own words.
a.
Primary productivity: The rate of production of organic compounds from photosynthetic organisms.
b.
Gross productivity: All the production results in the ecosystem.
c.
Net productivity: Resulting amount of the organic compounds in the end after some of it has been used.
_
3.
Why do we use dissolved oxygen as a measure of productivity? Does productivity include more than oxygen?
We use dissolved oxygen because it is easy to use in both photosynthesis and respiration. Yes, productivity also includes organic compounds.
4.
Using the diagrams below explain:
a.
How does putting a sample of pond water and algae/freshwater plants in the light enable us to measure gross productivity?
It enables us to show which is able to produce more products.
b.
How does putting a sample of pond water and algae/freshwater plants in the dark enable us to measure respiration?
It enables us to see which of the two uses up more oxygen.
c.
How does subtracting the two enable us to indirectly measure net productivity?
Net productivity are the results of oxygen being produced and taken in, so this enables us to measure the ending results.
5.
What are the three ways that primary productivity can be measured? Highlight the way will be used in this lab?.
a.
Measuring during photosynthesis
b.
Measuring during respiration when two O2 is being consumed.
c.
Subtracting gross productivity and respiration.
LAB PART 1: EFFECT OF TEMPERATURE ON DISSOLVED OXYGEN
We actually did this part of the lab already. Remind yourself of our experiment, our procedures, and our conclusions. We were investigating the effect of the physical factor of temperature on the percent dissolved oxygen in a body of water.
6.
What is the relationship between water temperature and dissolved oxygen?
- Warmer waters equals a more less amount of dissolved oxygen
7.
Explain why this relationship exists.
-Molecules in higher temperatures move a lot quicker making dissolved oxygen not being able to stay.
8.
So, now explain why the fish in the aquarium (on the LabBench Web site) above the radiator died?
-The fish drowned in water with no oxygen
A MODEL OF PRODUCTIVITY AS A FUNCTION OF DEPTH IN A LAKE
Now we are going to look at the biological factors that affect dissolved oxygen in a body of water. Look at the experimental design on the LabBench Web site (http://www.phschool.com/science/biology_place/labbench/lab12/model.html). We are taking a sample of pond water (with algae) and then modeling different depths in the pond by using screening to block out successive amounts of light. One hundred percent light for shallow depth, all the way to 0% light for deep ponds.
9.
Why do we take an initial reading of dissolved oxygen? What purpose does this serve in the experiment?
-Initial readings are used to check for change in the results
10.
Click on the “closer look” magnifying glass on the “initial bottle”. Why does the animation show oxygen being diffusing out of the freshwater plants? What does this signify?
- The oxygen shows the production of new air, this signifies photosynthesis
11. Click on the “closer look” magnifying glass on the foil- covered bottle. Why does the animation show oxygen diffusing into the freshwater plants? What does this signify?- The oxygen is being sucked into the plants. This shows respiration
12.
Click on the “closer look” magnifying glass on the 100% bottle under the light. Why does the animation show oxygen diffusing both into and out of the freshwater plants? What does this signify?
- This one also shows the production of new air. This signifies photosynthesis
ANALYSIS OF RESULTS
Let’s look at the results that will allow you to calculate the different types of productivity.
13. Measuring Respiration: Remember that plants (producers) perform both photosynthesis and respiration. To measure the amount of respiration that is happening in the bottle, we measure the amount of dissolved oxygen in the initial sample and then the amount of oxygen in the bottle kept in the dark. As shown in the illustration below, you then subtract the amount of dissolved oxygen in the “dark bottle” from the amount of dissolved oxygen in the “initial bottle” to calculate the amount of oxygen consumed in respiration. I have added some possible measurements to help. Explain why this calculation works.
- Because the initial bottle had more and the dark bottle ended up having less, this shows the net productivity of resulting in having less of the original since the plant absorbed the oxygen in the darkness.
14. Measuring Gross Productivity: Remember gross productivity is the total amount of sugars and oxygen produced by the plants in an ecosystem. I don’t like how this Web site shows you how to calculate gross productivity. The equation is correct, but it is a shortcut, so it makes it more difficult to understand. So follow me with the illustrations and the possible measurements below.
So the illustration shows us there was 10mg increase in dissolved oxygen in the jar as a result of photosynthesis in the last 24 hours and there was 5mg decrease in dissolved oxygen in the jar as a result of respiration in the last 24 hours. So the gross productivity (the full photosynthetic production in this ecosystem) of the algae in the bottle is the 5mg dissolved oxygen lost to respiration added back to the 10 mg dissolved oxygen accumulated in the bottle kept in the light. So what the algae really produced in the bottle was a total of 15mg dissolved oxygen, it just lost 5mg to respiration. And remember, the oxygen is an indirect measurement of the sugars produced in photosynthesis and lost in respiration.
10 mg oxygen gained
5 mg oxygen lost
15 mg oxygen as
+
=
from photosynthesis
to respiration
gross productivity
Now, in your own words, explain why this calculation works.
-Gross productivity, are the resulting products of all the losses and gains. Because the bottles gained 10 mg and lost 5 mg, the word of gross productivity being placed at the end shows that all productivity had a 15 mg amount altogether.
15. Measuring Net Productivity: Remember net productivity is the amount of sugars and dissolved oxygen produced by the plants in an ecosystem once you subtract out what the producers have consumed in respiration. So we actually already calculated that in the last example; I just called it “net photosynthesis.” Explain why this calculation works.
- The ending result of the lab shows the work of photosynthesis. Because the initial bottle started with less, the difference between the two show how much of a difference the resulted bottle ended with.
16.
Print out the completed calculation table from Sample Problem page of the LabBench Web site, fill in your predictions on the graph as well, and attach it to this lab to show me that you have completed it.
(Below)
17.
Print out the Lab Quiz and attach it to this lab to show me that you completed it.
SUMMARY QUESTIONS
(Below)
18.
Would you expect the dissolved oxygen levels in water sampled from a stream entering a lake to be higher or lower than the dissolved oxygen levels in water sampled from the lake itself? Explain.-I expect it to be higher as the stream entering the lake started at a higher point making the air more colder than at the lake.
19.
Would you expect the dissolved oxygen levels in water sampled from a lake at 7AM to be higher or lower than the dissolved oxygen levels in water sampled at 5PM? Explain.
- I would expect it to be higher as the sun has not risen high enough yet making the air more colder than in the after noon.
20.
One of the major sources of water pollution is the runoff from fertilizer used in agriculture and on suburban lawns as well as golf courses. In particular, the nitrogen and phosphorus nutrients in the fertilizer creates problems in the streams and ponds it flows into. They cause algal blooms and eutrophication in lakes.
a.
Why do nitrogen and phosphorus promote a lot of plant/algal growth?
- These minerals are considered food to the plants making them produce more.
b.
What is meant by algal bloom? (Look it up!)
- Algal bloom is the over population of the algae due to the overfeeding of the nutrients.
c.
What problems do algal blooms cause in ponds & lakes? Why isn’t a lot more producers a good thing? (Look it up!)
- Algal blooms end up covering the sunlight from reaching the depths of the water making it harder to synthesize.
d.
What is meant by eutrophication? (Look it up!)
- An excessive release of nutrients into lakes and ponds.
21.
At what depth—shallow or deep—will there be more primary productivity in a pond or a lake? Explain.
- More primary productivity will be in the shallow zone and sunlight is easier to reach.
22.
In an experiment, why do we use the mean of class data to make conclusions rather than individual student group data?
- We use class data to make conclusions because we can see a more broad set of data to average between.
23.
AP exam FRQ (2008). Consumers in aquatic ecosystems depend on producers for nutrition.
a.
Explain the difference between gross and net primary productivity.
-Gross productivity are the results of all losses and gains. Net productivity shows the difference between the initial and the resulting products.
b.
Describe a method to determine net and gross primary productivity in a freshwater pond over a 24-hour period.
- Net productivity: Record the data of the initial amount of organic compounds then record the data for the resulting amount. Subtract the two.
-Gross productivity: Add the amount of losses and gains of the resulting product.
c.
In an experiment, net primary productivity was measured, in the early spring, for water samples taken from different depths of a freshwater pond in a temperate deciduous forest.
Explain the data presented by the graph, including a description of the relative rates of metabolic processes occurring at different depths of the pond.
- The line on the graph shows the changing net productivity as the depth of the water increases. The line seems to be at its highest on the lowest water depth and gradually getting smaller in numbers the higher the depth of the water. At about thirty the net productivity ends up having a lower rate than the original number.
d.
Describe how the relationship between net primary productivity and depth would be expected to differ if new data were collected in mid-summer from the same pond. Explain your prediction.
- The net primary productivity would be a lot more higher. Though the deeper the water, the lower it would be , the numbers will still be higher than how it was back then. Because the sunlight is more closer to the water, more net productivity would be produced.
17: Quiz |