Question

7a) A monitoring group collects 12 samples on each of three dates from a local lake that is showing signs of eutrophication. They find that P concentrations average 0.82 mg/L and N concentrations average 11.90 mg/L. What macronutrient (N or P) is limiting and show how you determined your answer.

b) If allowed to continue unabated, what might be some of the effects of eutrophication of the lake? (Why should we care?) (2 pts)

c) What steps might you recommend to community leaders to reduce the effects of nutrient loading on the lake? You can think ‘outside the box’ here, but focus on the limiting nutrient. (2 pts)

Answer 1

7a) Limiting nutrient - missing or in short supply P or N .

P and N are usually limiting nutrients because plants require large amounts of them on a daily basis.

marine waters - nitrogen is the  limiting factor to algal production and eutrophication.

freshwater systems - Iphosphorus has been shown to be the limiting factor.

So here lake is a fresh water and P is the limiting factor.  

b) Eutrophication - algal blooms - block light from getting into the water. It also prevent oxygen from getting into the water, making it hypoxic. Aquatic plants and animals need both light and oxygen. Thus eutrophication  creating a dead zone where no organisms can survive due to the lack of light and oxygen.

c) Removing the algal bloom from lake.

Reducing the addition of sewage or other agricultural pollutants to the lake (like fertilizers).