Abstract

Harmful cyanobacterial blooms have been one of the most challenging ecological problems faced by freshwater bodies for more than a century. The use of satellite images as a tool to analyze these blooms is an innovative technology that will facilitate water governance and help develop measures to guarantee water security. To assess the viability of Sentinel-2 for identifying cyanobacterial blooms and chlorophyl-a, different bands of the Sentinel-2 satellite were considered, and those most consistent with cyanobacteria analysis were analyzed. This analysis was supplemented by an assessment of different indices and their respective correlations with the field data. The indices assessed were the following: Normalized Difference Water Index (NDWI), Normalized Differences Vegetation Index (NDVI), green Normalized Difference Vegetation Index (gNDVI), Normalized Soil Moisture Index (NSMI), and Toming’s Index. The green band (B3) obtained the best correlating results for both chlorophyll (R2 = 0.678) and cyanobacteria (R2 = 0.931). The study by bands of cyanobacteria composition can be a powerful tool for assessing the physiology of strains. NDWI gave an R2 value of 0.849 for the downstream point with the concentration of cyanobacteria. Toming’s Index obtained a high R2 of 0.859 with chlorophyll-a and 0.721 for the concentration of cyanobacteria. Notable differences in correlation for the upstream and downstream points were obtained with the indices. These results show that Sentinel-2 will be a valuable tool for lake monitoring and research, especially considering that the data will be routinely available for many years and the images will be frequent and free.

Highlights

  • Reservoirs are important freshwater reserves that have undergone highly negative impacts resulting in qualitative and quantitative changes in their physicochemical composition and impacts on fauna and flora

  • Notable differences in correlation for the upstream and downstream points were obtained with the indices

  • These results show that Sentinel-2 will be a valuable tool for lake monitoring and research, especially considering that the data will be routinely available for many years and the images will be frequent and free

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Summary

Introduction

Reservoirs are important freshwater reserves that have undergone highly negative impacts resulting in qualitative and quantitative changes in their physicochemical composition and impacts on fauna and flora As a result, their ecosystems undergo a process called eutrophication, which poses a major ecological challenge for freshwater bodies [1]. In the past few decades, the world’s freshwater ecosystems have suffered a steady increase in cyanobacteria blooms, which have multiplied rapidly as a result of eutrophication [4,5]. These are photosynthetic prokaryote organisms [6] that can produce a wide variety of toxic secondary metabolites known as cyanotoxins [7].

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