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Monitoring indigenous microalgae using derivative spectrophotometry and comparison with M. aeruginosa and C. vulgaris


 Derivative spectrophotometry was investigated as a monitoring tool for indigenous microalgae in surface waters. Absorbance spectra of indigenous microalgae were studied at low, medium and high range concentrations and were compared to the absorbance spectra of pure strains of M. aeruginosa and C. vulgaris to understand the differences in their absorbance fingerprints and the applicability of this method for real-time monitoring. Method Detection Limit (MDL) of the indigenous microalgae sample from its absorbance spectra was found to be 158,693 cells/mL. First derivative spectrophotometry was effective in detecting mixed indigenous microalgae at medium and high concentrations; however, it failed to differentiate between noise and signal at low concentrations. Subsequently, Savitzky-Golay algorithm was applied to improve the sensitivity and specificity of detection. The Savitzky-Golay first derivative of absorbance resulted in distinctive peaks and spectra fingerprints, indicating it can be used not only to monitor but also to identify various species of microalgae in water bodies. The Savitzky-Golay first derivative of absorbance also resulted in the lowest detection limits (60,170 cells/mL). Derivative spectrophotometry, along with mathematical and statistical tools, can be used for real-time detection and monitoring of mixed indigenous microalgae in surface waters.