Fluorescence in the estimation of chlorophyll-a in public water reservoirs in the Brazilian cerrado

Abstract

Context

The usual strategy for monitoring of eutrophication process is the use of traditional limnological methods, based on laboratory analysis. These procedures involve costly and time-consuming analyses, usually with in vitro methodologies, which can still have limitations in terms of sensitivity and reliability, if poorly managed. Phytoplankton pigments, such as chlorophyll-a (Chl-a), are highly fluorescent and can provide the environmental status of water bodies.

Aims

This study aims to analyse, compare and evaluate an estimation of Chl-a through fluorescence in public water sources in the Brazilian cerrado. Exploratory statistical analyses were conducted by using absolute fluorescence units (AFU) and relative fluorescence units (RFU) compared with traditional laboratory data (standard procedure for the determination of Chl-a by spectroscopic methods) to evaluate the significance of differences in estimating Chl-a concentration. Subsequently, empirical models, based on spectral band combinations, were generated to convert fluorescence measurement in Chl-a concentration, by linear regression.

Key results

The generated model found a strong correlation and coefficient of determination (r = 0.88; R² = 0.78). The efficiency of the model was also confirmed by statistical indicators (RMSE = 1.27, MAPE = 26.72 and BIAS = −6.32).

Conclusions

We concluded that the estimate of Chl-a through RFU was better than through AFU.

Implications

Therefore, based on the results of this study, it is recommended that RFU be used to obtain more precise and accurate estimates of Chl-a concentration through empirical models based on linear regression.