Environmental Science Foundations and Applications, 1st 1.From Chapter 1, Your n
ID: 234107 • Letter: E
Question
Environmental Science Foundations and Applications, 1st
1.From Chapter 1, Your neighbor has fertilized her lawn. Several weeks later, she is alarmed to see that the surface of her ornamental pond, which sits at the bottom of the sloping lawn, is covered with a green layer of algae.
(a) Suggest a feasible explanation for the algal bloom in the pond.
(b) Design an experiment that would enable you to validate your explanation. Include and label in your answer:
(i) a testable hypothesis.
(ii) the variable that you will be testing.
(iii) the data to be collected.
(iv) a description of the experimental procedure.
(v) a description of the results that would validate your hypothesis.
(c) Based on the data from your experiment and your explanation of the problem, think of, and suggest, one action that your neighbor could take to help the pond recover.
Explanation / Answer
Ans:
(a) Algae can be a major problem in ponds, causing discoloured water, green scum at the pond edges, or dense mats of green growth under the surface. If conditions are favourable, algae will spread quickly and can harm aquatic life.
It is most likely that too much fertilizer was applied to the lawn. When it rained, some of the run-off flowed down the sloping lawn and entered the ornamental pond. This increased the nutrient supply in the pond and resulted in an algal bloom a few weeks later.
Symptoms:
There are many different symptoms, depending on the algae present. These are the most common symptoms:
The problem:
Most ponds will have an algal problem at some time or another, but it thrives where pools have been created in a sunny position, with very little planting to provide shade across the surface.
It also forms when there are too many nutrients in the water. This could be due to:
Algae can be promoted by using tap water to fill or top-up ponds; ideally use rainwater. The cause of this is unclear, but might be related to the chlorine content affecting the natural balance of the pond.
Prevention:
Aim to reduce the amount of nutrients entering the pond by the following:
(b)
An example experiment could be: The experiment will test the hypothesis that fertilizer will promote the growth of pond algae in water. The variable that will be tested is the amount of fertilizer that will be added to each experimental group. The data that will be collected is the amount of algae growth in each of the experimental groups.
The experiment will be performed using the following procedure:A sample of the pond water is obtained and filtered through a paper towel. The algae left on the paper towel is transferred to a container of distilled water (1L) and mixed thoroughly.50 mL of the diluted algae solution is measured into five identical small clear glass containers. The following amounts of fertilizer are put into the containers and mixed thoroughly:
0.00 g into container 1
0.25g into container 2
0.50g into container 3
0.75g into container 4
1.00g into container 5
The above steps are repeated another three times to use up all of the 1L of the algae mixture and providing a total of four experimental groups. That is, the experiment is repeated four times. The containers with no (0g of) fertilizer represent the control group.Each of the labeled glass containers is placed on a sunny windowsill and monitored on a daily basis. The glass containers are compared for algal growth by assessing the green coloration of each container. (This could be done qualitatively as described above and/or compared to the color of 50ml of water taken directly from the surface of the pond with the algal bloom OR quantitatively by using a colorimeter if one is available.)It is expected that between 3 and 7 days, depending on the amount of sunlight, more algal growth will be evident in the containers that have fertilizer added to them. The amount of algae will depend on the amount of fertilizer that was added—the more fertilizer, the more algae. This result validates the hypothesis that fertilizer will promote the growth of pond algae in water.
(c) It may be difficult to get the pond to recover immediately due to the high level of fertilizer that was added to the lawn. The algae growth may continue until all the fertilizer has run-off from the lawn. The neighbor should NOT apply any more fertilizer to the lawn. This needs to use a soil test kit and assess the nutrient levels of the lawn. Using a mulching lawn mower will help restore nutrient levels naturally.The algae in the pond could be harvested or scooped off when it is in a quantity that enables this to occur. This could also be done in conjunction with drawing down the level of the pond water and replacing it with freshwater. This will help dilute the nutrient level in the pond. it could also plant vegetation on the side of the pond that is facing up the slope. This will help reduce nutrient input from run-off water when it rains, as the nutrients will be taken up by the plants before run-off enters the pond.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.