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Assessment of Field and Laboratory Methods for the Detection and Analyses of Cyanobacteria and Cyanotoxins in Texas Reservoirs, 2020

March 4, 2022

In cooperation with the Texas Commission on Environmental Quality (TCEQ), the U.S. Geological Survey (USGS) used various field and laboratory methods to determine the presence and concentration of cyanobacteria, cyanotoxins, and taste-and-odor compounds in selected Texas water bodies. This data release documents the results from water-quality samples collected from 12 water bodies in Texas during water year 2020 (WY20) and 2021 (WY21). A water year is defined as the 12-month period from October 1 through September 30 and is designated by the calendar year in which it ends. Both qualitative and quantitative field and laboratory methods were performed. Analyses included phytoplankton taxonomy, measurements of phytoplankton biomass, and concentrations of cyanotoxins, taste-and-odor compounds, and photosynthetic pigments. Water-quality samples were also collected to provide supporting data and document existing conditions. These supporting data included dissolved solids, major ions, nutrients, and organic carbon. Water-quality samples were analyzed for total cyanotoxin concentrations (anatoxin, cylindrospermopsin, domoic acid, microcystin [total and 10 congeners], nodularin, okadaic acid, and saxitoxin), taste-and-odor compound concentration (2-Methylisoborneo [MIB] and geosmin), chlorophyll a, pheophytin a, major ions (calcium, chloride, fluoride, magnesium, potassium, silica, sodium, and sulfate), and nutrients (nitrogen, phosphorous, and multiple species of each nutrient). Analyses of cyanobacterial and cyanotoxin gene concentrations are included. An In-Situ Aqua TROLL multiparameter sonde was deployed concurrently with a YSI EXO2 multiparameter sonde to provide two sets of field values that can be compared. Each reservoir had one sampling site. At each site, depth-integrated samples were collected using a peristaltic pump integrating through the photic zone. The photic zone is the depth when measured irradiance is 1 percent of the irradiance measured at the surface of the water column. Water-quality field properties were measured using the multiparameter sondes at 1-foot intervals in the water column through the photic zone (the upper layer of a water body where there is sufficient sunlight penetration to support photosynthesis), then at 5-foot intervals to the bottom of the water column. Three rapid-assessment field kits were used to determine semi-quantitative values of three cyanotoxins (anatoxin, cylindrospermopsin, and microcystin) at each sampling site. Chlorophyll-a and pheophytin-a were analyzed by the Trinity River Authority Central Laboratory in Dallas, Texas. Cyanobacterial and cyanotoxin genes were analyzed by the USGS Ohio Water Microbiology Laboratory in Columbus, Ohio. The USGS Organic Geochemistry Research Laboratory in Lawrence, Kansas analyzed for cyanotoxins and taste-and-odor compounds. PhycoTech, Inc. in St. Joseph, Michigan analyzed phytoplankton taxonomy and biomass. Taxonomic names within this data release are from PhycoTech's taxonomic naming convention and may differ from the taxonomic names listed in the Integrated Taxonomic Information System database (ITIS, 2022). Engineering Performance Solutions in Jacksonville, Florida analyzed for MIB and geosmin. Samples were analyzed for suspended solids, nutrients, and major ions by the USGS National Water Quality Laboratory (NWQL) in Denver, Colorado. Water-quality field properties (water temperature, dissolved-oxygen concentration, pH, specific conductance, turbidity, chlorophyll florescence (RFU & density), phycocyanin florescence (RFU & density), irradiance, and Secchi depth) were also measured at each sampling site. NWQL terms "parameter codes" and "parameter descriptions" were retained in the water-quality dataset when referring to water-quality field properties and constituents.

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