Abstract
Algal blooms in freshwater ecosystems can negatively impact aquatic and human health. Satellite remote sensing of chlorophyll a (Chl-a) is often used to help determine the severity of algal blooms. However, satellite revisit flyover schedules may not match the erratic nature of algal blooms. Studies have paired satellite and ground-based data that were not collected on the same day, assuming Chl-a concentrations did not change significantly by the flyover date. We determined the effects of an increasing time window between satellite overpass dates and field-based collection of Chl-a on algorithms for Landsat 5, Landsat 8, and Sentinel-2, using 14 years (2006–2020) of Chl-a data from 10 Oklahoma reservoirs. Multiple regression models were built, and selected statistics were used to rank the time windows. The Sentinel-2 results showed strong relationships between Chl-a and satellite data collected up to a ±5-day window. The strength of these relationships decreased beyond a ±3-day time window for Landsat 8 and a ±1-day time window for Landsat 5. Our results suggest that the time window between field sampling and satellite overpass can impact the use of satellite data for Chl-a monitoring in reservoirs. Furthermore, longer time windows can be used with higher resolution (spatial, spectral) satellites.
Highlights
This study focused on 10 of the Beneficial Use Monitoring Program (BUMP) reservoirs, which were selected because they had enough available chlorophyll a (Chl-a) data for the time windows considered in the study
None of the three satellites met the mum threshold (N = 30) for pairing and development of regression models based on th minimum threshold (N = 30) for pairing and development of regression models based on confirmedthe theneed need expand window beyond th the
Chlorophyll-a is present in all major groups of algae and is used as a key indicator of algal blooms in inland water bodies [37]
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Algal blooms dominated by cyanobacteria have the potential to negatively impact aquatic ecosystems [1]. Some species of cyanobacteria produce toxins that adversely impact human and animal health [2]. Algal blooms can create anoxic conditions in the water column when they die and undergo microbial decomposition, resulting in fish kills and adverse impacts on other aquatic organisms [3]. Algal blooms cause economic losses due to beach closures and the loss of recreational activities associated with the affected waters [4,5]
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