Interpretation of total phytoplankton and cyanobacteria fluorescence from cross‐calibrated fluorometers, including sensitivity to turbidity and colored dissolved organic matter

Abstract

In vivo pigment fluorescence methods allow simple real-time detection and quantification of freshwater algae and cyanobacteria. Available models are still limited to high-cost fluorometers, validated for single instruments or individual water bodies, preventing data comparison between multiple instruments, and thus, restricting their use in large-scale monitoring programs. Moreover, few models include corrections for optical interference (water turbidity and colored dissolved organic matter, CDOM). In this study, we developed simple models to predict phytoplankton and cyanobacterial chlorophyll a (Chl a) concentrations based on Chl a and C-phycocyanin in vivo fluorescence, using multiple low-cost handheld fluorometers. We aimed to: (1) fit models to mixed cyanobacterial and microalgal cultures; (2) cross-calibrate nine fluorometers of the same brand and series; (3) correct the CDOM and turbidity effects; and (4) test the algorithms' performance with natural samples. We achieved comparable results between nine instruments after the cross-calibration, allowing their simultaneous use. We obtained algorithms for total and cyanobacterial Chl a estimation. We developed parametric corrections to remove CDOM and turbidity interferences in the algorithms. Five sampling sites (from a lake, a stream, and an estuary) were used to test the algorithms using eight cross-calibrated fluorometers. The models showed their best performance after CDOM and turbidity corrections (total Chl a: R 2 = 0.99, RMSE = 7.8 μg Chl a L −1 ; cyanobacterial Chl a: R 2 = 0.98, RMSE = 9.8 μg Chl a L −1 ). In summary, our models can quantify total phytoplankton and cyanobacterial Chl a in real time with multiple low-cost fluorometers, allowing its implementation in large-scale monitoring programs.

Las floraciones de cianobacterias tóxicas comprometen el uso del agua del Río Negro, Uruguay

“…Diversos métodos, de alta frecuencia y de bajos costos, pueden proporcionar información orientativa o semi-cuantitativa en tiempo real, como el monitoreo visual en zonas de recreación de la ciudad de Mercedes (sitio 15, Figura 1) (Uruguay. Ministerio de Vivienda Ordenamiento Territorial y Medio Ambiente; DINAMA, 2019b), el monitoreo remoto o la medición de la fluorescencia de pigmentos in vivo (Cremella, et al, 2018;Aubriot, et al, 2020).…”

“…Las réplicas (n = 3) se aclimataron ~ 40 horas a 25 ± 2 °C, 110 -115 µmol fotón m -2 s -1 y fotoperíodo 16:8, luz:oscuridad y se ordenaron al azar. Durante los 10 días de incubación se siguieron los cambios de la fluorescencia in vivo de la Clo a y la ficocianina (Cremella, et al, 2018) para calcular la tasa de crecimiento (en día -1 ). Al finalizar (10 días), parte de las muestras se fijaron con solución lugol para el conteo de fitoplancton, y el resto se congeló para el análisis de MC totales mediante la técnica ELISA (Brena, et al, 2021).…”

Consistency of six in situ, in vitro and satellite-based methods to derive chlorophyll a in two optically different lakes

“…For example, a significant overestimation of C Chl-a with increased organic matter concentrations in an estuary was shown by Goldman et al (2013). Results by Cremella et al (2018) showed a linear response between ChlF and a CDOM (440) up to 20 m −1 and a non-linear response between ChlF and CDOM at a CDOM (440) > 20 m −1 , also noting the negligible effect in CDOM ranges (a CDOM (440) < 2 m −1 ) and pointing out the lack of interaction between turbidity and CDOM effects. In Saadjärv, the effect of CDOM and non-algal particles can be considered negligible.…”

Recientes aplicaciones de la fluorescencia de la clorofila en los cultivos vegetales

“…Dichas mediciones se obtienen con equipos denominados fluorómetros los cuales miden la fluorescencia de la clorofila en hojas individuales o en las plantas enteras [2]. Los fluorómetros son equipos diseñados para la emisión y detección de longitudes de onda de radiación que son absorbidas y reemitidas por los pigmentos de los organismos que llevan a cabo fotosíntesis oxigénica; tales como cianobacterias, algas, y plantas vasculares [3]. Con el análisis de las características de la radiación reemitida por los pigmentos fotosintéticos puede determinarse la Eficiencia en el Uso de la Radiación (EUR); la disminución en la EUR generalmente ocurre por un estado de estrés.…”