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Early Warning of Microcystin Criteria Exceedance in Harmful Algal Blooms
Citation:
Wymer, L. Early Warning of Microcystin Criteria Exceedance in Harmful Algal Blooms. 2019 UNC Water Microbiology Conference, Chapel Hill, NC, May 14 - 16, 2019.
Impact/Purpose:
Concerns about increasing occurrences and severity of harmful algal blooms (HAB) have been heightened due to health and ecological effects. One interest is in how to predict when HABs may occur in a water body for initiating remedial or preventative measures, such as shutting off water intake. This presentation illustrates a method for monitoring and early warning using molecular method, qPCR, which may be incorporated in an array for routine monitoring. Relatively inexpensive and easy to perform on a routine basis, this would be of interest to municipalities, counties and states as a screening procedure for the imminent occurrence of an HAB.
Description:
Increasing occurrence of cyanobacterial harmful “algal” blooms in all 50 states has led to heightened public concern because due to potential ecological and health impacts. Recreational exposure to microcystins (MC) produced by cyanobacteria indicate a range of potential health effects in humans including headaches, fever, joint pain, diarrhea, stomach cramps, and allergic reactions which may occur shortly after exposure to days later. Chronic hepatotoxic, neurotoxic and dermatoxic effects have also been noted. A US EPA Health Advisory cutoff of 0.3 µgL-1 for children has been established for microcystins in drinking water. Cyanotoxin testing methods include ELISA and LC/MS methods. The use of qPCR and RT-qPCR enables rapid and high throughput detection of microcystin producers (MCers). A study on MC and MCers was conducted using a panel of qPCR assays targeting mcyA, E and G on weekly water samples from an Ohio inland lake during May through September, 2015. Early warning of MC exceedance of the Advisory Level was using operating characteristic curves for ELISA or LC/MS/MS based exceedance. A one-week early warning of MC exceedance was made by qPCR and RT-qPCR results. With respect to either general or specific toxic MCers, qPCR “predictive power” (percent uncertainty explained) was 60% with respect to LC/MS/MS base exceedance and 50%, with respect to ELISA-based exceedance. RT-qPCR methods demonstrated lower predictive powers ranging 24 to 44%. Compared to a commonly used Youden criterion for establishing a ROC cutoff, this would result in about 50% reduction in LC/MS/MS analyses required for a false negative rate of 4% relative to qPCR. Examination of other lag periods between (RT-)qPCR and MC measurement seem to be consistent with a day-of-the-week effect, in that power peaked around the seven-day lag, although daily data were limited, obtained only during June in the study.
