Monitoring Sargassum Inundation on Beaches and Nearshore Waters Using PlanetScope/Dove Observations

Abstract

<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Sargassum</i> beaching events have been reported in recent years around the Caribbean Sea and FL, USA, causing numerous environmental and economic problems. Satellite remote sensing has been widely used to monitor <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Sargassum</i> blooms in open waters, yet due to either coarse spatial resolution or low-revisit frequency, it is difficult to provide timely information on <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Sargassum</i> inundation from traditional satellite instruments. In this study, we demonstrate the capacity of 3-m resolution daily Dove imagery in monitoring <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Sargassum</i> beaching events on Miami beach (FL, USA) and Cancun beach (Mexico). A U-net deep learning (DL) computer model is developed to extract <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Sargassum</i> features from Dove imagery over beaches and nearshore waters. Application of the model to Dove image sequences between May and August 2019 shows two major inundation events on both Miami beach and Cancun beach, consistent with local reports. With the availability of 3-m resolution PlanetScope/Dove and PlanetScope/SuperDove data around the globe, the findings suggest that it is possible to monitor dynamic inundation events of not only <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Sargassum</i> but also other macroalgae in many other regions.