How Does Varying The Concentration Of Nitrates Affect The Growth Of Chlorella?

Background Information:

Living organisms need nitrogen to survive, as it makes up several biological structures such as DNA. In its gaseous form, nitrogen is unusable to living organisms in this form, and must undergo a process called nitrogen fixation to be transformed into ammonia and nitrate ions. Nitrates in the soil are necessary for plant growth.

Through the Haber process, nitrogen fixation can now occur through human activity to produce fertilizer. Fertilizers are widely used by farmers to provide crops with a more abundant source of important nutrients like nitrates. With a growing population and demand for crops, an increase in fertilizer use is occuring to meet these demands; as a result, an increase in nitrates is also occurring. However, nitrates included in fertilizer are soluble in water and can be carried in runoff from rainfall into bodies of waters such as lakes. Some scientists are now concerned about nitrate contamination, which can lead to harmful lake eutrophication. In this process, plants like algal blooms take over the environment. In this investigation, I will be exploring how the concentration of nitrates affects the growth of Chlorella (a single-celled type of algae). I will measure the growth through the presence and size of any algal blooms that may develop. From my results, I will be able to deduce not only if nitrates affect algae growth, but at what specific concentration they lead to harmful algal blooms. From this point, I will be able to speculate on the importance of nitrate contamination.