Various Pollutants And The Effects On Algal Growth Biology Essay

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Pollutants are an everyday occurrence in our ecosystem. Water pollution especially is the most common pollution existing today. It can come in many forms and end up in every water source due to everyday human activity. There are a myriad of causes of water pollution. Some of these causes include, farmers using chemicals to enhance the growth of their crops (Krantz 2009). These fertilizers then are run down into our water system through rain. As a result this causes a sudden growth in algae. Also industrial processes produce toxic waste which will then cause acid rain. When acid rain falls it dramatically disrupts the pH of water sources (Largen 2010). This will cause a rapid decrease in the growth of algae.

Overall the exceeding growth of algae uses up a great deal of oxygen, causing other living organisms in the body of water to suffer. "Even overgrowths of non-toxic types of algae can block the sunlight from penetrating the water's surface, which makes it difficult for marine life to find food, causing eventual death (Withgott 2008)."

The purpose of the research described here is to evaluate the effects pollutants have on algal growth. Comparing the amount of algal growth that results from the exposure to different concentrations of different pollutants is the main goal of this experiment. Using the spectrometer, measurements of each vial of water and the pollutants within will be taken. Since pollutants result in either an increase or decrease in algal growth; algal growth will increase as the concentration of nitrogen and phosphorous pollution increases and decrease as the concentration of acid rain pollution increases.


Before starting the experiment, 7 test tubes that were previously prepared 2 weeks prior to this experiment were obtained. There was a control tube, two separate ones with low and high nitrogen content, two more with low and high phosphorous concentration and 2 with low and high acid rain concentrations making a total of 7 test tubes. Prior to using the spectrometer, each separate test tube needed to be filled with distilled water by a cuvette ¾ full. To thoroughly mix the substances the test tube needed to be moved at the base in 10cm circles for 10 seconds. After, the spectrometer needed to be set at a wavelength of 450nm and each test tube is to be placed inside the spectrometer to read the absorbance. It is extremely important to make sure each test tube was wiped clean on the outside before being placed in the spectrometer to get the most accurate readings.

It was vital to also remember that each tube should have been done one by one and as accurately as possible to get the best results. Mixing the contents was a possibility and must have been avoided by labeling what was in each test tube. Once the experiment was complete, the contents of the cuvette were returned back to the sample test tube from which it came. Each cuvette was then rinsed with distilled water and put away in its proper place. The data recorded was the absorbance (at 450 nm) of control versus pollutant treatment by concentration and lab group.

Overall the data collected is used to determine how each pollutant effects algal growth in each test tube. It is important to recognize that each pollutant with different concentrations will result in different amounts of algal growth.


There is an obvious distinction that the pollutants with higher concentrations caused greater algal growth, while the pollutants with lower concentrations caused lower algal growth (Refer to Table 1). The presence of acid rain disrupted algal growth as well and showed that as the concentration of acid rain rose there was a significant decrease in algal growth. For example, for group number 4 their control showed a measurement of -.6 the higher concentrations of pollutants such as High Nitrogen showed a result of -.89 which shows that higher concentrations of nitrogen pollutant causes higher algal growth. For the acid rain results once again group 4 control tube measured -.6 the high concentration of Acid Rain resulted in the absorbance measurement of -.59 which as a results explains that higher concentrations of acid rain causes a decrease in algal growth. Furthermore, each group achieved different results.


Absorbance (at 450 nm)

Presence of Algal Growth

Lab Group #


Low Nitrogen

High Nitrogen

Low Phosphorous

High Phosphorous

Low Acid Rain



















































The expected result of this study was that, since pollutants result in either an increase or decrease in algal growth; algal growth will increase as the concentration of nitrogen and phosphorous pollution increases and decrease as the concentration of acid rain pollution increases. From the results of the experiment this statement is supported by all the groups' except for groups 1 and 3. This could have been because they did not perform the experiment accurately in regards to adding distilled water to the test tubes or wiping them clean before placing them in the spectrometer. Groups 2, 4, 5 and 6 supported the hypothesis. Since there were more groups who supported the hypothesis anybody can infer that this hypothesis is true.

When water sources are polluted by various substances and chemicals it can cause a disruption in the chemistry of the water. Access nutrients such as phosphorous from fertilizers or nitrogen can provide algae with extra nutrients causing it to grow rapidly. As a result when the access algae die they deplete the water source they are in of oxygen killing the animal and plant life within it.