A Study of Metal Nanoparticle Toxicity on Algae

Nanoparticles are small particles that behave as a whole, depending on their properties. All nanoparticles have many applications in industries, but they are being released into the environment as pollutants. This is known as nanopollution, a type of pollution where nanoparticles are released into the environment. The nanoparticles are mostly released into the environment through production accidents and the release of industrial byproducts into the environment. As a result of nanopollution, these nanoparticles can impact the biological processes of different organisms, and can also alter the chemistry of the ocean. Algae is an extremely important marine organism, since it produces 70-80% of the oxygen on Earth, and can be used as a potential energy resource for the future, to make biofuels. Two main species of algae used to make biofuels are Botryococcus braunii and Chlorella vulgaris. The purpose of the experiment was to analyze the effects of metal nanoparticle toxicity on algae--specifically Botryococcus braunii and Chlorella vulgaris. The experiment was taken a step further by testing the potential of the algae to make biofuel under the conditions of nanopollution. The null hypothesis stated that the algae would not react to metal nanoparticle pollution at all, whereas the alternative hypothesis stated that metal nanoparticles would have a negative or positive effect on the algae. The independent variables were the type and concentration of metal nanoparticles being used: no nanoparticles (control), and silver, gold, copper, zinc, and magnesium, each at concentrations of 5%, 10%, and 15%. Over the course of 10 trials, the dependent variables measured were pH, kH and ppm (carbonate hardness), CO₂, algae growth (cells and cell counts), wet weight, dry weight, and chlorophyll absorbance. An additional step in the project consisted of using a mathematical model to estimate algae lipid yield under the conditions of nanoparticle toxicity.  Results were that as the concentration of the nanoparticles increased, the growth rates decreased (cells per drop and cell counts). Wet weight,CO₂ yields, and chlorophyll absorbance decreased, and so did dry weight and the estimated lipid yield, as the nanoparticle concentration increased. kH and pH increased as the nanoparticle concentration increased, meaning that the algae were not converting as much CO₂ to oxygen, hindering their rates of photosynthesis. Algae in low concentrations of nanoparticles had better cell structure than algae in high concentrations of nanoparticles. Overall, the null hypothesis was rejected, and it was concluded that the algae were impacted negatively by metal nanoparticle toxicity. When nanoparticles concentrations increased, the algae could not adapt to the polluted conditions of nanoparticles in their environment, and were poisoned by them, severely impacting the biological functioning of the algae. As a result, they started to die off faster, and could not adapt to the conditions of toxicity in their environment.