Elemental Analysis of Masculinized Fish Collected around Fort Myers, Florida by X-ray Fluorescence (XRF) Spectroscopy

Brenna Hilborn, Nora Demers, Ju Chou

Department of Chemistry and Physics, Florida Gulf Coast University
Department of Biology, Florida Gulf Coast University
Department of Chemistry and Physics, Florida Gulf Coast University

The masculinization of fish, or the conversion from genetic females to males, can be caused by many factors, including many environmental stressors and chemical pollution. In female Mosquitofish (Gambusia holbrooki), masculinization is evidenced by an increase in the ratio of anal fin ray 4 to anal fin ray 6. Ideally, the ratio in females should be 1:1; however, fish samples collected from various locations in local Southwest Florida communities around Fort Myers, FL showed ratios mostly greater than 1.2 in all locations. This study aims to analyze elements present in masculinized Gambusia holbrooki to determine whether a correlation exists between elevated levels of toxic metals and masculinization. During the period from March 10, 2021, to February 18, 2022, a total of 27 Gambusia holbrooki samples were collected from various locations around Fort Myers, FL including septic communities, the Florida Gulf Coast University campus, reuse communities, and multiple golf courses. X-ray fluorescence (XRF) spectrometry was used to analyze the concentrations of 18 major and trace elements: barium, chromium, copper, iron, manganese, lead, rubidium, antimony, selenium, strontium, titanium, zinc, phosphorous, sulfur, chlorine, potassium, calcium, and iodine. From this data, we were able to determine that fish samples collected from golf course lakes and effluents have higher concentrations of copper than samples collected from the other locations tested. The average copper concentration from our ten golf course samples is 19.2 ppm, while the average copper concentration of the 17 samples from other locations was only 6.18 ppm. This distinction may be due to the use of copper sulfate (CuSO₄) by golf course communities to treat their stormwater ponds to kill algae that may be growing.

I am graduating on Saturday, May 6, not May 9.