Growing, Growing Gone: The Effect of Adding Excess Nutrients on Dissolved Oxygen Content in Water

Abstract

Biofuels research and Aquatic Quality Collaborative (BiRAQC) has a research division concerned with eutrophication in Oklahoma freshwater sources and questions what conditions lead to eutrophic algae blooms. Through our knowledge of biology we know that phosphorus and nitrogen, nutrients found in agricultural fertilizers, are limiting agents for algae growth and we wanted to experiment this to determine how dissolved oxygen levels are affected when excess phosphorus and nitrogen are added to water from Lake Dolese in Oklahoma in the form of fertilizer. To test this question we gathered six samples of water from Lake Dolese and designated two control samples that received no fertilizer, two samples that contained moderate amounts of fertilizer, and two samples that contained high amounts of fertilizer and took an initial dissolve oxygen measurement before letting them sit on a windowsill for one week. After the week-long trial period was over, we collected final dissolved oxygen levels in each sample and recorded our results onto a graph. We found that when moderate amounts of fertilizer were added to the samples there was a decrease in dissolved oxygen content and when high amounts of fertilizer were added to the samples there was an increase in dissolved oxygen levels.  This means that algae growth only occurred when there were excessive amounts of nutrients in the sample.