Evaluation of nutrient concentrations and genetic presence of cyanobacteria and their cyanotoxins in Lake Onalaska

Abstract

Aquatic cyanobacteria blooms are becoming a global environmental concern due to their ability to produce secondary metabolites in the form of toxins. It is important to determine the abundance of genes specific to cyanobacteria and their cyanotoxins in eutrophic lakes before any potential blooms emerge. Increased levels of PO4 3- -P NH4 +/NH3 -N, and NO3 -/NO2 --N have been linked with cyanobacteria abundance. A cyanobloom can be associated with other factors such as increased temperature, low dissolved oxygen, and elevated pH. Not every eutrophic lake is monitored monthly or even yearly for cyanobacteria presence due to the lack of cyanoblooms. This study examined Lake Onalaska, a eutrophic lake, located in pool 7 on the Mississippi River. Water samples were collected twice a month, from July 2021 to September 2021, at four different sites for genetic and nutrient analysis. The nutrient data was comparable to other eutrophic Wisconsin lakes. Lastly, qPCR found that Site 3 in early September had 1025 cyanobacterial 16S rRNA gene copies per mL, while all other sample sites were below the detectable limit value. No cyanotoxin genes were detected at any site sampled.