Abstract
Several groups of microorganisms are capable of producing toxins in aquatic environments. Cyanobacteria are prevalent blue green algae in freshwater systems, and many species produce cyanotoxins which include a variety of chemical irritants, hepatotoxins and neurotoxins. Production and occurrence of potent neurotoxic cyanotoxins β-N-methylamino-l-alanine (BMAA), 2,4-diaminobutyric acid dihydrochloride (DABA), and anatoxin-a are especially critical with environmental implications to public and animal health. Biomagnification, though not well understood in aquatic systems, is potentially relevant to both human and animal health effects. Because little is known regarding their presence in fresh water, we investigated the occurrence and potential for bioaccumulation of cyanotoxins in several Nebraska reservoirs. Collection and analysis of 387 environmental and biological samples (water, fish, and aquatic plant) provided a snapshot of their occurrence. A sensitive detection method was developed using solid phase extraction (SPE) in combination with high pressure liquid chromatography-fluorescence detection (HPLC/FD) with confirmation by liquid chromatography-tandem mass spectrometry (LC/MS/MS). HPLC/FD detection limits ranged from 5 to 7 µg/L and LC/MS/MS detection limits were <0.5 µg/L, while detection limits for biological samples were in the range of 0.8–3.2 ng/g depending on the matrix. Based on these methods, measurable levels of these neurotoxic compounds were detected in approximately 25% of the samples, with detections of BMAA in about 18.1%, DABA in 17.1%, and anatoxin-a in 11.9%.
Highlights
Cyanobacteria, or blue-green algae, are microscopic organisms occurring in both freshwater and marine environments
Ibelings et al [58] indicated that anatoxin-a is less likely to occur in fish and seafood, and even less in samples taken from freshwater, which is consistent with a lack of detections for anatoxin-a in any of the fish samples collected in this study
Both in 2009 and 2010, BMAA, DABA, and anatoxin-a were detected in 15 aquatic plant samples; these results were the first to be reported for all three cyanotoxins in Nebraska freshwater ecosystems
Summary
Cyanobacteria, or blue-green algae, are microscopic organisms occurring in both freshwater and marine environments. Cox et al [41] showed that the algal neurotoxin BMAA can be produced by all known groups of cyanobacteria in both symbiotic and free-living forms Their data showed that Nostoc can exist as symbionts with host plants such as cycads, some flowering plants such as Gunnera, and other cyanobacteria such as Synechocystis and Anabaena, found in U.S. Cyanotoxins have been show to co-occur with drinking water taste-and-odor compounds, such as geosmin and 2-MIB in 91% of blooms sampled in a regional study of Midwestern lakes and impoundments [51]. The present study was conducted to evaluate the potential for occurrence of neurotoxic cyanotoxins in Nebraska lakes and reservoirs, as well as associated plant and fish tissue collected during two summers, when cyanobacteria blooms are prevalent. The present study provides a snap shot of the occurrence of these compounds in lake water and in aquatic organisms likely to serve as a route of human exposure
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