Abstract
In the past two decades, both microscopic algae (i.e., phytoplankton) and larger algae (i.e., macroalgae) have increased in certain coastal and open ocean waters, yet a comprehensive picture at the global scale is lacking. Here, we address this challenge by analyzing 1.2 million satellite images with computer artificial intelligence to quantify macroalgal mats and microalgal scums in global oceans between 2003 and 2022. With a total cumulative realized niche area of 43.8 million km2, macroalgae blooms in the tropical Atlantic and western Pacific both expanded at unprecedented rates since the 2010s (13.4% per year since 2003). Although slower, the annual expansion rate of microalgae scums is also statistically significant (1.0% per year since 2003). Such tre…
Abstract
In the past two decades, both microscopic algae (i.e., phytoplankton) and larger algae (i.e., macroalgae) have increased in certain coastal and open ocean waters, yet a comprehensive picture at the global scale is lacking. Here, we address this challenge by analyzing 1.2 million satellite images with computer artificial intelligence to quantify macroalgal mats and microalgal scums in global oceans between 2003 and 2022. With a total cumulative realized niche area of 43.8 million km2, macroalgae blooms in the tropical Atlantic and western Pacific both expanded at unprecedented rates since the 2010s (13.4% per year since 2003). Although slower, the annual expansion rate of microalgae scums is also statistically significant (1.0% per year since 2003). Such trends are likely a result of ocean warming and eutrophication, with a possible regime shift favoring macroalgae and specialized species of microalgae. These findings have broad implications on ocean ecology, carbon sequestration, environments, and economy.
Data availability
All satellite data used in this analysis is available through the NASA OB.DAAC (https://oceancolor.gsfc.nasa.gov). The environmental data used in this analysis is available through their specific data providers (https://disc.gsfc.nasa.gov/datasets/M2T1NXAER_5.12.4/summary; https://www.ncei.noaa.gov/access/world-ocean-atlas-2018/bin/woa18oxnu.pl). The software used to process satellite data is SeaDAS (version 8.2, https://seadas.gsfc.nasa.gov). All satellite data used in the training and validation of the deep-learning model to detect floating algae from MODIS images has been made available through a public data repository62 (https://doi.org/10.17632/f39zt9g2c4.1), including the spectral reflectance data, quick-look images, “ground truth” images, and model output images. The global floating algae maps used in this study are made available through the figshare repository63 (https://doi.org/10.6084/m9.figshare.28139492). Source data are provided with this paper.
Code availability
All computer codes to process satellite data are available through SeaDAS (version 8.2, https://seadas.gsfc.nasa.gov). The Python and MATLAB codes to train the DL model and analyze time-series data are available from the corresponding author upon request.
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Acknowledgements
This work was supported by the U.S. NASA (80NSSC20M0264 (C.H.), 80NSSC24K1507 (C.H.), 80NSSC25K7361 (B.B.B.), 80NSSC25K7427 (C.H.), 80NSSC24K0893 (J.I.G.), 80NSSC25K7239 (J.I.G.)), the U.S. NOAA (NA23NOS4780291 (B.B.B.)), the U.S. EPA (02D42923 (B.B.B.)), and the U.S. Joint Polar Satellite System (JPSS) program (ST133017CQ0050_1332KP22FNEED0042 (L.Q.) and ST13301CQ0050/1332KP22FNEED0042 (C.H.)). We thank the U.S. NASA OB.DAAC for providing all satellite data and thank the NASA OBPG for providing the SeaDAS software to enable this analysis. The scientific results and conclusions, as well as any views or opinions expressed herein, are those of the author(s) and do not necessarily reflect those of NOAA or the Department of Commerce.
Author information
Authors and Affiliations
NOAA Center for Satellite Applications and Research, College Park, MD, USA
Lin Qi & Menghua Wang 1.
Global Science & Technology Inc., Greenbelt, MD, USA
Lin Qi 1.
College of Marine Science, University of South Florida, St. Petersburg, FL, USA
Brian B. Barnes, Yuyuan Xie & Chuanmin Hu 1.
University of Southern California, Los Angeles, CA, USA
Douglas G. Capone 1.
Lamont Doherty Earth Observatory, Columbia University, Palisades, NY, USA
Joaquim I. Goes 1.
Estuary & Ocean Science Center, Biology Department, San Francisco State University, Tiburon, CA, USA
Edward J. Carpenter
Authors
- Lin Qi
- Menghua Wang
- Brian B. Barnes
- Douglas G. Capone
- Joaquim I. Goes
- Edward J. Carpenter
- Yuyuan Xie
- Chuanmin Hu
Contributions
Conceptualization: C.H. and L.Q.; Methodology: L.Q. and C.H.; Investigation: L.Q. and C.H.; Visualization: L.Q., C.H., B.B.B., and M.W.; Writing – original draft: L.Q.; Writing – review and editing: L.Q., M.W., B.B.B., D.G.C., J.I.G., E.J.C., Y.X., and C.H.
Corresponding author
Correspondence to Chuanmin Hu.
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Nature Communications thanks Konstantinos Topouzelis, who co-reviewed with Spyros Spondylidis and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. A peer review file is available.
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Cite this article
Qi, L., Wang, M., Barnes, B.B. et al. Global floating algae blooms are expanding. Nat Commun (2025). https://doi.org/10.1038/s41467-025-66822-5
Received: 05 February 2025
Accepted: 13 November 2025
Published: 07 December 2025
DOI: https://doi.org/10.1038/s41467-025-66822-5