Which of the following human activities could contribute to the eutrophication of a lake? (Check all that apply.)A) Dumping piles of leaves near a lakeB) Planting trees around the periphery of the lakeC) Washing clothes with soap in the lakeD) Feeding the ducks in the lakeE) Dumping plastic trash into the lakeF) Fertilizing lawns near the lake

Question

What will be an ideal response?

Answer 1

A, C, D, F

Clarify Question
• What is the key concept addressed by the question?
        o This question addresses eutrophication.
• What type of thinking is required?
        o This question is asking you to analyze the information given, using logic, to dissect the problem and determine the answer.

Gather Content
• What do you already know about eutrophication?
        o Eutrophic bodies of water are high in algal nutrients and often populated densely with algae. They are more likely to be low in dissolved oxygen, especially in summer. In a eutrophic body of water, decay microbes often place high demands on the oxygen available because when thick populations of algae die, large amounts of organic matter are made available for decomposition. Moreover, light does not penetrate eutrophic waters well because of all the organic matter in the water; photosynthetic oxygen addition is therefore limited to just a relatively thin layer of water at the top.
        o Human activities have often transformed oligotrophic lakes into eutrophic ones. For example, when people overfertilize their lawns or fields, nitrate and phosphate from the fertilizers wash off into local water systems. Lakes that receive these nutrients become more eutrophic. When excessive nitrates and phosphates enter rivers and lakes, the character of the bodies of water is changed for the worse; the concentration of dissolved oxygen declines, and fish species such as carp take the place of more desirable species. The problem is exacerbated when rivers empty into the ocean. The eutrophication caused by the accumulation of chemicals can lead to enormous areas of water with no oxygen, causing massive die-offs of fish and other animals.

Choose Answer
• Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
        o Any activity that increases nutrient input into the lake causes eutrophication. Planting trees would likely slow runoff into the lake reducing nutrient input. Plastic would not affect nutrient levels.
        o Dumping piles of leaves near a lake would add the nutrients that were in the leaves.
        o Washing clothes with soap in the lake would add phosphorus because detergents have phosphates.
        o Feeding the ducks in the lake would add nutrients from the food.
        o Fertilizing lawns near the lake would add nutrients from the fertilizer (usually N, P, and K).

Reflect on Process
• Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
        o The question required you to analyze the information given, using logic, to dissect the problem and determine the answer.
        o Did you recognize that anything that increase nutrient levels will contribute to eutrophication?