posted on 2024-01-11, 13:35authored byKevin
M. Stroski, Daniel L. Roelke, Crista M. Kieley, Royoung Park, Kathryn L. Campbell, N. Hagen Klobusnik, Jordan R. Walker, Sierra E. Cagle, Jessica M. Labonté, Bryan W. Brooks
Though toxins produced during harmful blooms of cyanobacteria
present
diverse risks to public health and the environment, surface water
quality surveillance of cyanobacterial toxins is inconsistent, spatiotemporally
limited, and routinely relies on ELISA kits to estimate total microcystins
(MCs) in surface waters. Here, we employed liquid chromatography tandem
mass spectrometry to examine common cyanotoxins, including five microcystins,
three anatoxins, nodularin, cylindrospermopsin, and saxitoxin in 20
subtropical reservoirs spatially distributed across a pronounced annual
rainfall gradient. Probabilistic environmental hazard analyses identified
whether water quality values for cyanotoxins were exceeded and if
these exceedances varied spatiotemporally. MC-LR was the most common
congener detected, but it was not consistently observed with other
toxins, including MC-YR, which was detected at the highest concentrations
during spring with many observations above the California human recreation
guideline (800 ng/L). Cylindrospermopsin was also quantitated in 40%
of eutrophic reservoirs; these detections did not exceed a US Environmental
Protection Agency swimming/advisory level (15,000 ng/L). Our observations
have implications for routine water quality monitoring practices,
which traditionally use ELISA kits to estimate MC levels and often
limit collection of surface samples during summer months near reservoir
impoundments, and further indicate that spatiotemporal surveillance
efforts are necessary to understand cyanotoxins risks when harmful
cyanobacteria blooms occur throughout the year.