How do phosphorus and nitrogen levels affect dissolved oxygen content in pond water?

Abstract

Eutrophication of bodies of water has become an increasingly prevalent issue all over the world. The primary driver of this issue is the increase in plant nutrients, mainly phosphorus and nitrogen, which cause algal blooms that have undesirable consequences such as causing poor water quality and fish kills. In this experiment, we tested the levels of dissolved oxygen in samples of water from a nearby pond with different concentrations of phosphorus and nitrogen. We attempted to link our findings to explain why eutrophication causes decreased levels of dissolved oxygen in bodies of water. We found that after two weeks, the dissolved oxygen level of the water had increased significantly, so we added a decomposer to our samples to mimic natural decomposers found in pond. Our results showed a substantial decrease in the dissolved oxygen level after the decomposer was added to each sample.