Cyanobacterial HAB Monitoring using Satellite Imagery for the United States Great Lakes region created by the NOAA Harmful Algal Bloom Forecasting Branch (HAB-F) from 2000 to 2024 (NCEI Accession 0312614)

Cyanobacterial Harmful Algal Blooms (CyanoHABs) are an ongoing threat to water quality, ecosystems, economies, and public health in the Great Lakes region, especially in Lake Erie, Sandusky Bay, Saginaw Bay in Lake Huron, Green Bay in Lake Michigan, and Lake Winnebago. Long-term time series data are required to characterize bloom phenology, assess trends in phenological changes, and understand the key drivers that cause and exacerbate blooms. A 25-year, continuous, and cross-sensor-consistent satellite-based time series (2000–2024) of cyanobacterial harmful algal bloom (cyanoHAB) observations is presented for the United States Great Lakes region. This time series was created using data from multiple satellite ocean color sensors, specifically Envisat-Medium Resolution Imaging Spectrometer (MERIS), Sentinel-3A/B OLCI, and Moderate Resolution Imaging Spectroradiometer (MODIS)-Terra. To bridge the observational gap between the MERIS and Ocean and Land Color Instrument (OLCI) sensors, the Cyanobacteria Index (CIcyano) was derived from MODIS-Terra using CyanNet, a science-informed deep learning framework, and harmonized with CIcyano products from MERIS and OLCI.