Análise e predição da concentração de clorofila A em reservatórios do semiárido

Abstract

This dissertation presents an evaluation of the dynamics of chlorophyll a (Cla) in reservoirs of the Brazilian semi-arid region, seeking to understand the factors that influence its production in tropical reservoirs and the development of simple models capable of predicting satisfactorily the concentration and peaks of Cla. First, we analyzed the determination coefficients (R²) between total phosphorus (PT) and Cla through linear regression simple, verifying the statistical performance of the models generated for the hydrographic basins and reservoirs. The results showed that, even following the trend of classic curves, PT is not a satisfactory predictor of Cla when considered in isolation, with R² influenced by different basins, volumetric variability and Cla concentrations. A variance of R² reservoirs of different sizes and trophic state in relation to phosphorus total was not significant. Then, the same methodology was applied to the total nitrogen (NT), verifying that this is a better predictor of Cla than PT, being the R² influenced mainly by hydrographic basins, volumetric variation and by the change in water levels. trophic state. The results also indicated that, even in reservoirs limited by PT, NT can be a satisfactory predictor of chlorophyll a, indicating a possible co-limitation between the nutrients. Finally, in the last study carried out, the spatiotemporal variations were determined in the concentration of chlorophyll a using models that integrate variables hydroclimatic and nutrient changes through simple models to predict the temporal dynamics and the Cla concentration peaks. The equations show different responses of Cla to the variables input according to the conditions to which the reservoirs may be subjected, to mention: sediment resuspension, water column stratification, wind action, etc. The application of model to the two largest reservoirs studied showed greater sensitivity of Cla to changes in water use classes in terms of NT variations, followed by PT, volume of reservoir and daily precipitation. The combination of the presented studies provides a broad advance in understanding the dynamics of chlorophyll a in tropical reservoirs and the effect combination of nutrients and hydroclimatic variables in the production of cyanobacteria in reservoirs can promote more efficient management of eutrophication control.