Remote Sensing of Harmful Algal Blooms in the Indian River and Connected Waterways in Brevard County

In 2021, Brevard County Natural Resources Management Department (BCNRMD) was awarded the Florida Department of Environmental Protection (FDEP) Water Protection Grant INV14 for development of innovative technologies to address Harmful Algal Blooms (HAB). With an increasing frequency of HAB occurrences in the Indian River Lagoon (IRL) over the last decade, the identification of bloom triggers and behaviors is vital to County efforts to manage the watershed. The County selected Applied Ecology, Inc (AEI) for the use of remote sensing technologies as a cost-effective and encompassing approach to providing rapid identification of HAB formation, the lifecycle of the HAB, and then identify hotspots of HAB occurrences.

The purpose of this project is to provide the framework for the retrieval, processing, and analysis of the European Space Agency (ESA) Sentinel-2 and Sentinel-3 satellite data over the Brevard County sections of the IRL (Figure 1). AEI will review the available academic literature on HAB assessment using the Sentinel satellites and then evaluate the identified methodologies for their applicability to the IRL. These findings will be utilized to generate weekly HAB updates to BCNRMD (Figure 2) and perform a long-term spatiotemporal statistical analysis of historical HABs and corresponding water quality parameters. The data collected and analyzed for this project will be made available to interested agencies and researchers through an ArcGIS Online web application.

Starting in 2022, AEI began flying a Harris Aerial Carrier HX8 UAS equipped with a BaySpec OCI-F hyperspectral camera to collect high spatial and spectral resolution imagery of the IRL and selected tributaries and canals. AEI also collected in-situ hyperspectral readings of a variety of benthic environments and water column conditions during UAS flights using an OceanOptics FLAME VIS-NIR spectrometer. AEI closely coordinated with the St Johns River Water Management District (SJRWMD) to collect corresponding remote sensing data during their ongoing monthly surface water sampling. Additionally, AEI performed rapid analysis of HABs during 2022 utilizing the UAS and spectrometer, with water quality samples to be collected for algal enumeration. This data was used to further evaluate and refine the previously reviewed remote sensing analysis methods, identifying unique spectral features of HABs and any confounding signals from water column or benthic conditions.

Figure 1: INV14 Study areas within Brevard County, Florida
Figure 2: Example imagery of Sentinel-2 uncalibrated Normalized Difference Chlorophyll Index (NDCI) over the southern Banana River area on October 30, 2020, during a large Harmful Algal Bloom (HAB) event.