Toxin producing cyanobacterial blooms have increased globally in recent decades in both frequency and intensity. Despite the recognition of this growing risk, the extent and magnitude of cyanobacterial blooms and cyanotoxin prevalence is poorly characterized in the heavily populated region of southern California. Recent assessments of lentic waterbodies (depressional wetlands, lakes, reservoirs and coastal lagoons) determined the prevalence of microcystins and, in some cases, additional cyanotoxins. Microcystins were present in all waterbody types surveyed although toxin concentrations were generally low across most habitats, as only a small number of sites exceeded California’s recreational health thresholds for acute toxicity. Results from passive samplers (Solid Phase Adsorption Toxin Tracking (SPATT)) indicated microcystins were prevalent throughout lentic waterbodies and that traditional discrete samples underestimated the presence of microcystins. Multiple cyanotoxins were detected simultaneously in some systems, indicating multiple stressors, the risk of which is uncertain since health thresholds are based on exposures to single toxins. Anatoxin-a was detected for the first time from lakes in southern California. The persistence of detectable microcystins across years and seasons indicates a low-level, chronic risk through both direct and indirect exposure. The influence of toxic cyanobacterial blooms is a more complex stressor than presently recognized and should be included in water quality monitoring programs.

The global proliferation of toxin producing cyanobacterial blooms has been attributed to a wide variety of environmental factors with nutrient pollution, increased temperatures, and drought being three of the most significant. The current study is the first formal assessment of cyanotoxins in two impaired lakes, Canyon Lake and Lake Elsinore, in southern California that have a history of cyanobacterial blooms producing high biomass as measured by chl-a. Cyanotoxins in Lake Elsinore were detected at concentrations that persistently exceeded California recreational health thresholds, whereas Canyon Lake experienced persistent concentrations that only occasionally exceeded health thresholds. The study results are the highest recorded concentrations of microcystins, anatoxin-a, and cylindrospermopsin detected in southern California lakes. Concentrations exceeded health thresholds that caused both lakes to be closed for recreational activities. Cyanobacterial identifications indicated a high risk for the presence of potentially toxic genera and agreed with the cyanotoxin results that indicated frequent detection of multiple cyanotoxins simultaneously. A statistically significant correlation was observed between chlorophyll-a (chl-a) and microcystin concentrations for Lake Elsinore but not Canyon Lake, and chl-a was not a good indicator of cylindrospermopsin, anatoxin-a, or nodularin. Therefore, chl-a was not a viable screening indicator of cyanotoxin risk in these lakes. The study results indicate potential acute and chronic risk of exposure to cyanotoxins in these lakes and supports the need for future monitoring efforts to help minimize human and domestic pet exposure and to better understand potential effects to wildlife. The frequent co-occurrence of complex cyanotoxin mixtures further complicates the risk assessment process for these lakes given uncertainty in the toxicology of mixtures.

SPATT has been developed and tested for a variety of resins (see review by Kudela, 2017). These Standard Operating Procedures (SOP) outline the use of the resin DIAON HP20 since it has been demonstrated to quantify microcystins, anatoxin-a, saxitoxin, domoic acid, and okadaic acid in fresh, brackish, and marine waters, all from the same SPATT sampling device (Lane et al. 2010; Miller et al. 2010, Kudela 2011, Gibble and Kudela, 2014, Howard et al., 2017, Kudela, 2017, Peacock et al., 2018). Cylindrospermopsin and nodularin have also been detected using SPATT with DIAON HP20 resin in California, however, the use of DIAON HP20 for these toxins has not been well characterized in the laboratory. This methodology is ready for wider adoption by the research, monitoring, and management communities interested in detecting and tracking the dynamics of freshwater and marine toxins. The SOP described herein for the assemblage and construction of SPATT bags can be used for deployment in freshwater, brackish and marine environments and the extraction process described below is for the analysis of both marine toxins and cyanotoxins.

SPATT has been developed and tested for a variety of resins (see review by Kudela, 2017). These Standard Operating Procedures (SOP) outline the use of the resin DIAON HP20 since it has been demonstrated to quantify microcystins, anatoxin-a, saxitoxin, domoic acid, and okadaic acid in fresh, brackish, and marine waters, all from the same SPATT sampling device (Lane et al. 2010; Miller et al. 2010, Kudela 2011, Gibble and Kudela, 2014, Howard et al., 2017, Kudela, 2017, Peacock et al., 2018). Cylindrospermopsin and nodularin have also been detected using SPATT with DIAON HP20 resin in California, however, the use of DIAON HP20 for these toxins has not been well characterized in the laboratory. This methodology is ready for wider adoption by the research, monitoring, and management communities interested in detecting and tracking the dynamics of freshwater and marine toxins. The SOP described herein for the assemblage and construction of SPATT bags can be used for deployment in freshwater, brackish and marine environments and the extraction process described below is for the analysis of both marine toxins and cyanotoxins.

Domoic acid (DA), produced by Pseudo-nitzschia diatoms, is the one of the major toxin threats from harmful algal blooms (HABs) on the west coast of the United States. DA events vary in magnitude, timing, and duration, and elucidating drivers for individual events is a persistent challenge. Monterey Bay experiences near-annual DA events and hosts long-term HAB monitoring at the Santa Cruz Municipal Wharf (SCW). Here we characterize two toxin events, occurring in May 2023 and March 2024. The events were similar in magnitude and duration, but an exploration of physical, biological, and chemical dynamics revealed distinct environmental drivers. These differences resulted in a significant deviation in cellular DA (cDA) within the same species of Pseudo-nitzschia. In addition, opportunistic solid-phase adsorption toxin tracking (SPATT) was used for environmental metabolomics. The novel application of SPATT revealed 159 metabolites that were strongly correlated with DA in both events and produced a spectral match to a new marine natural product using Global Natural Products Social Molecular Networking (GNPS). This work takes a multivariable approach to understanding toxin drivers and lends proof of concept for the integration of environmental metabolomics in HAB monitoring.