Benjamin Gallion, “Determining Phosphorus Concentration in Wisconsin Beach Sand and Its Impact on E. coli Abundance”
Mentor: Sandra Mclellan, Freshwater Sciences
Poster #66
Freshwater beaches are a popular Wisconsin destination for tourism and recreation. Bacteria such as Escherichia coli (E. coli) are used as indicators of fecal pollution at beaches, as it is found in high concentrations in human and mammal feces. It is also easily quantifiable, so it is used by many beach management programs. E. coli can persist in the sand, confounding beach management practices. Therefore, it is important to understand how E. coli survives within a beach environment. E. coli can also grow in sand independently of fecal pollution using nutrients such as carbon, nitrogen, and phosphorous found within the sand. In this study, we examined how phosphorus contributes to the growth of E. coli by analyzing phosphorus levels and corresponding E. coli abundance of sand samples collected from six beaches in Southeast Wisconsin over three months in the summer of 2023. Each sand sample was mixed with DI water and passed through a mixed cellulose filter, and the filtrate was analyzed for phosphorus levels using a spectrophotometer. We found that phosphorus concentrations ranged between 0.35μg/g to 44.91μg/g of sand. Harrington Beach had significantly higher total dissolved phosphorus than Port Washington and Simmons Island, (Kruskal Wallis, p <0.05). E. coli counts, Harrington beach had the second lowest E. coli levels, with Port Washington having the lowest E. coli counts of all the beaches. coli abundance over the summer ranged from 0.56 to 1.93 Log(CFU/g sand). Results were not as expected, as Harrington Beach had the lowest E. coli concentrations, with also the highest phosphorus concentrations. This data suggests that phosphorus alone does not significantly impact E. coli growth and survival in beach sand, more testing with different nutrients is needed to understand how nutrients impact E. coli concentrations.