Comparative evaluation of ELISA, PPIA, and HPLC/MS for microcystin quantification in seven lakes of western Michigan

Cyanobacterial harmful algal blooms (cHABs) pose escalating risks to aquatic ecosystems and public health through the release of microcystins (MCs), emphasizing the need for accurate detection and quantification. This study compared three widely used MC detection methods-enzyme-linked immunosorbent assay (ELISA), protein phosphatase inhibition assay (PPIA), and high-performance liquid chromatography coupled with mass spectrometry (HPLC/MS)-across about 200 samples from seven drowned river mouth lakes in western Michigan, USA. Results revealed that PPIA and ELISA overestimated the concentration of MC-LR. Specifically, the measurement error of MC-LR equivalent by ELISA and PPIA increased at low concentrations (<0.15 μg/L HPLC/MS-quantified MC-LR) but remained relatively stable at higher levels. Further analysis revealed that among the MC congeners, MC-RR showed the highest contribution rate (60%) to the measurement error by ELISA, while MC-YR showed the highest contribution rate (69%) for PPIA. These discrepancies correlated strongly (p < 0.001) with cyanobacterial composition (notably Microcystis dominance), bloom intensity, and lake trophic status. Method selection should therefore consider congener composition, community structure, and nutrient conditions. A tiered analytical framework-using ELISA for rapid screening, PPIA for bioactivity assessment, and HPLC/MS for confirmatory quantification-offers a robust approach for reliable toxin monitoring, while integration with watershed nutrient management can further mitigate cHAB risks and protect freshwater ecosystem health.