| dc.description.abstract | Cyanotoxins and taste-and-odor (T&O) compounds are produced by cyanobacteria, including benthic varieties that grow on the bed of freshwater streams. Cyanotoxins, such as microcystin, anatoxin-a, and saxitoxin, can poison or even cause death if consumed in high quantities, while T&O compounds, such as geosmin and 2-Methylisoborneol (MIB), can cause a noxious taste and smell in drinking water. The negative effects of cyanotoxins and T&O compounds have the potential to worsen as the effects of climate change and urbanization add additional pressures to already sensitive stream ecosystems. Understanding how urbanization impacts the production of cyanotoxins and T&O compounds is crucial to lowering the impact these metabolites have on our health, safety, and environmental well-being. To understand this relationship, we surveyed three streams in the rapidly urbanizing Johnson County, KS, which range from highly rural to highly urban. A total of nine benthic algae mats were sampled repeatedly over the summer and early fall of 2021. Benthic algae mat locations were analyzed using a combination of in situ sensors and laboratory testing to assess the production of cyanotoxins and T&O compounds as well as the potential physicochemical and biological drivers of this production. Water quality parameters, including temperature, pH, specific conductivity, and nutrients, were measured during field visits as were benthic algae parameters, including cyanobacterial concentration, taxonomic make-up, stable isotopes, toxin analysis, and genetic analysis. To explain the drivers of toxin and T&O production, we develop predictive linear regression and random forest models. The results of our field sampling showed widespread prevalence of cyanotoxins and T&O compounds, irrespective of upstream land use to a benthic mat. Microcystin and geosmin were detected in every benthic algae sample we collected, whereas anatoxin-a, saxitoxin, and MIB were found in 65%, 26%, and 84% of samples, respectively. Results of the linear regression and random forest models generally indicate that toxin gene abundance, cyanobacteria abundance, temperature, and specific conductivity are the dominant predictors of microcystin, anatoxin-a, and saxitoxin production, and that cyanobacteria abundance, temperature, and specific conductivity are the dominant predictors of geosmin and MIB production. In summary, our results show that any human-derived environmental impact, whether it be urbanization or ruralization, can lead to the occurrence of microcystin, anatoxin-a, saxitoxin, geosmin, or MIB within freshwater benthic cyanobacteria. Cyanotoxin and T&O compound forming benthic algae appear to be a common feature of human-disturbed environments and our results can assist with informing water utility and municipality managers with cyanobacterial monitoring strategies and remediation. | |
