VIIRS image of algae blooms from STAR.
Scientists from NOAA’s Center for Satellite Applications and Research (STAR), in collaboration with partners such as the University of South Florida (USF), are pairing artificial intelligence with more than one million satellite images to detect and quantify surface floating seaweed and phytoplankton scums in global oceans. The results from 2003 to 2022 help scientists better understand the spatial extent and long-term changes of these surface-floating marine plants that can negatively impact the economies along our nation’s coasts.
Most algae species’ growth peaks in the spring and summer seasons. Their optimal growth is determined by things such as water temperature and the amount of nutrients in the water. Increases in the amount of nutrients – from sources like agriculture and sewage runoff – and warmer water temperatures can both fuel extensive blooms. While moderate blooms may benefit ocean ecology and fisheries, extensive and longer-lasting ones can be harmful to the environment and marine organisms. Such harmful blooms impact the ocean economy which consists of tourism, commercial and recreational fishing, and related goods and services in coastal communities.
In a recently published scientific paper, the scientists observed the floating seaweed and phytoplankton surface scums in tropical and subtropical regions in the Atlantic, Pacific and Indian Oceans as well as in some marginal seas. These surface blooms were in both coastal and open waters, occupying a cumulative area of 44 million square kilometers, more than four times the size of the United States. This is the first time a complete quantified picture of floating algae has been obtained for the global ocean.
Global distribution of floating algae derived from satellite observations. (Figure from Qi et al., Nat Commu, 2026)
The study was inspired by a collaborative effort between STAR and USF back in 2019 when they added a new ocean color data product to the STAR’s Ocean Color Viewer (OCView) tool. This new data product enabled a global qualitative view of floating algae for the first time. Yet, it was difficult to determine the surface area these algae covered. STAR scientists realized they required a more quantitative study to further understand floating algae and their changing patterns.
Left image is a micrograph of green Noctiluca scintillans cells. The right image is the surface bloom of green Noctiluca scintillans observed in the Arabian Sea.
The need to fill in the data gaps at a global scale is essential to predict and manage algal blooms, benefiting the ocean economy. With rapid development of satellite remote sensing technology and computer models, STAR hopes to continue the research by including more satellite data and other computer models to better observe and understand the biological and physical processes of the increasing blooms.