Measurable microcystin in Ozark streams was rare during summer 2018 baseflow conditions

Abstract

Accelerated eutrophication due to human activity has been linked to an increase in the occurrence of cyanobacteria in freshwater systems. The purpose of this study was to document the occurrence of microcystin, a common cyanotoxin, within northwest Arkansas streams. Twenty streams were sampled from May through October 2018, and water and periphyton samples were analyzed for microcystin and chlorophyll-a (CHL-a). Mean microcystin concentrations in water samples were low across sites, ranging from < 0.10 to 0.21 μg L −1 . Mean microcystin in the periphyton across sites ranged from 2.6 to 9.9 μg m −2 and were within values observed in the literature. All microcystin concentrations measured in these Ozark streams were well below the current USEPA recreational guidelines of 8.0 μg L −1 and the drinking water guidelines of 0.3 μg L −1 for infants and 1.6 μg L −1 for adults.

Total Microcystin Concentration Variability in Water Samples and Recommended Minimum Volume (20 mL) for Freeze Thaw Cycles

“…Cyanobacterial harmful algal blooms (cyanoHABs) have been and continue to be a research focus across the USA and globe, where scientists are trying to understand the drivers in cyanobacterial toxin production. These blooms have been observed in freshwaters, mainly lakes, across the USA (Loftin et al 2016b), but toxins can be measurable in streams (Loftin et al 2016a; Graham et al 2020; Austin and Haggard 2022). While toxins from cyanoHABs in lotic systems tend to be low, occurrences of elevated toxins, particularly total microcystins, have been reported in large rivers, e.g., Obryzyca River, Poland (Czyzewska et al 2020) and Poteau River, Arkansas, USA (Haggard, B.E., unpublished data).…”