Liberty Ansorge, “Characterization of Dissolved Organic Matter in a Eutrophic Coastal Lagoon”
Mentor: Laodong Guo, Freshwater Sciences
Veterans Park Lagoon, a closed ecosystem near the Milwaukee Harbor belonging to the coastal system of Lake Michigan has shown evidence of increased levels of eutrophication, or a richness of nutrients and minerals. Determinants of the levels of eutrophication in coastal lagoons include the seasonal cyanobacterial blooms and their respective causality in increased nutrient levels. For this study, weekly water samples were collected from the lagoon from June 2019 to October 2019. The filtered samples were then run through a fluorescence spectrophotometer and a UV–Visible spectrophotometer. The parameters used for this study fall into the category of dissolved organic matter (DOM). Measurements of components such as chlorophyll-a, dissolved organic carbon (DOC), colored dissolved organic matter (CDOM), and humification contribute to quantitative and qualitative findings. Results show that seasonal variability and its effect on water temperature cause changes in these levels. In comparison to its neighbor, Lake Michigan, Veterans Park Lagoon has a larger euphotic zone, causing more light penetration and therefore, higher levels of CDOM within the bulk DOM. The aromatic humic components of DOM allow for fluorescence as they absorb the UV light and we expect a high DOM level in this lagoon because of the large quantity of algal biomass present. Additionally, the positive relationship between seasonal transitions and biomass levels exemplify parameters in which we can further explore the effects of dissolved organic matter on an increased prevalence of nutrient pollution. Other occurrences such as precipitation, surface runoff, and recreational use also affect algal biomass and water quality. Long term observation of these parameters and others may lend some insight into the relationships detected and the overall health of this unique body of water.
Hi everyone! My name is Liberty and I’m a second-year student studying biology on the pre-med track at UWM. I have been working with Dr. Guo and graduate student, Hui Lin since September of last year and have had a wonderful time learning from these mentors! I hope you enjoy my presentation!
Hi Liberty. I enjoyed your poster! One question I had…since you are looking at dissolved organic matter, how did you process the samples, i.e. presumably they were filtered before analysis to remove particulate material? Some filter will bind organics, so this could be an issue in some cases, especially where there is very high organic matter.
Thanks, John Berges (Biological Sciences.
Hi there! I’m glad you enjoyed it! Yes, the water samples were filtered through pre-combusted (550 °C for 4 hours) and pre-weighed 0.7-μm GF/F filters.
Great presentation, Liberty. With Milwaukee being a major city catering to many residents, students, and tourists, I wonder how similar (or different) the measured levels of DOM and CDOM in Veterans Park Lagoon are to other lagoons in less populated areas or different regions. Through your research, do you have any insights or thoughts?
Hi Matthew! Thank you for your question. This is something I had pondered because this lagoon is located in a highly populated area and is even used for recreational activities. These factors would undoubtedly affect the health and DOM/CDOM levels of any body of water, especially one like this, but due to the short sampling period, I am not sure our data can be representative of this quite yet. Dr. Guo has a few publications that provide data that I utilized during my research and they pertain to this concept. They provide a comparative analysis on similar parameters of some other bodies of water including the Yukon River, the Milwaukee River, and Veterans Park Lagoon. They were quite helpful in making sense of how different locations or regions, even just in Wisconsin, may result in some interesting data that can be tied to population density, pollution, etc.