Click On Any Station
SaWS Map Image Bermuda Eastern Caribbean Jamaica Yucatan Panama Guadeloupe Martinique SECOORA Western Gulf of Mexico Central Atlantic
You will be redirected to the data for that station.
Two Sargassum Species
Two Sargassum Species
Two species of sargassum are found in the caribbean.
Sargassum natans (left) and Sargassum fluitans (right).
Photo by Gulf Coast Research Laboratory — University of South Mississippi
Beach Cleanup
Beach Cleanup
Costly efforts to remove the excessive Sargassum

   SaWS Clickable Map

This project is called the Sargassum Watch System and is based on derived satellite data. It's goal is to provide scientists and other interested parties the ability to track Saragassum in near-real time.

Pelagic Sargassum seaweed is a brown macroalgae floating on the ocean surface. Comprised primarily of two species, S. natans and S. fluitans, it is abundant in the Intra-Americas Sea (IAS), the Atlantic, and along the coasts of British Isles and mainland Europe. In the ocean it serves as an important habitat for many marine animals as it provides food, shade, and shelter (from predators) to fish, shrimp, crabs, and turtles. Sargassum may serve as fertilizers for sand dunes and thus protects shoreline stability. It is also a marine resource for other uses such as biomass for food, fuel, and as a possible source of pharmaceutical materials.

However, excessive amounts of Sargassum on beaches in populated areas can cause a lot of problems and they must be physically removed. Sargassum decomposition on beaches smells bad, attracts insects, and causes many environmental problems (e.g., smothering turtle nesting sites, sea turtle mortality, fish kills) and economic problems (e.g., diminished tourism). The beaches along the Texas coast have experienced Sargassum inundation events annually, and since 2001 beaching events have also occurred on many Caribbean shores in nearly every spring and summer (links to photos). Sargassum beaching events have also been reported in western Africa and northern Brazil. Monitoring Sargassum distribution and abundance in the ocean in a timely fashion is of great importance for studying ocean ecology, helping fishery management, and forecasting Sargassum beaching events. The SaWS is meant to provide such a function through producing and sharing customized satellite imagery in near real-time in a user-friendly way.

   SaWS Clickable Map

The table below shows the four satellite sensors that are currently used in SaWS, with the first three sharing similar characteristics.

Sensor Revist Frequency Spacial Resolution (m) Spectral bands for
floating algae (nm)
Spectral bands for
color index
MODIS/Terra Near daily 1000 667, 748, 869 469, 555, 645 2000 — present
MODIS/Aqua Near daily 1000 667, 748, 869 469, 555, 645 2002 — present
VIIRS Daily 750 671, 745, 862 443, 551, 671 2012 — present
Landsat 8 OLI 16-day 30 655, 865, 1609 443, 561, 655 2013 — present

The raw satellite data are provided by the U.S. NASA and USGS. These data are downloaded and processed through a Virtual Antenna System (VAS, link to IEEE weblink for the paper) using both standard and customized algorithms. Of particular importance are the two customized data products, namely the floating algae index (FAI, link to Hu 2009 paper at RSE website) to detect floating algae and other materials on the ocean surface, and the color index (CI, link to Hu 2011 paper at AGU website) to trace ocean circulation features. Floating algae often appears as outstanding image slicks over the relatively homogeneous background, while ocean circulation patterns may be inferred from the various eddy and plume features. Two examples are given below.

Derived Satellite Data Samples
Floating Algae Index Ocean Circulation CI
Floating Algae Index (left) reveals algae and Color Index (right) shows circulations patterns

   SaWS Clickable Map

All data products can be accessed freely under “Satellite Data Products” at or by clicking the menu item with the same name to the left. This is the Virtual Antenna System (VAS). To facilitate visualization and navigation, these products are divided into different geographic regions, for example Central Atlantic, Eastern Caribbean, Western Gulf of Mexico, Bermuda, etc. You may click on any of the "SaWS Clickable Map" buttons found in every tab to have a clickable map to the various regions. Then, a user can select a specific date on the calendar, or use the “animate” function to browse through the image sequence quickly to determine the date of interest. A screenshot of a typical web interface is presented below.

Virtual Antenna Web Interface
Virtual Antenna Web Interface
Virtual Antenna System At the Optical Oceanography Laboratory

   SaWS Clickable Map

In each of the images you will find in the VAS (previous tab) you will note a small GE and globe in the lower right corner. When this is clicked, a KML file is generated for the image you are looking at. In addition to satellite imagery, surface currents from the Hybrid Coordinate Ocean Model (HYCOM — from the National Ocean Partnership Program (NOPP)) are obtained, updated nightly, and made available via the VAS as a layer to the satellite imagery. All data products can be displayed in Google Earth with a simple mouse click (see example below), thereby facilitating visualization and navigation. Within Google Earth, once a Sargassum raft is identified with latitude and longitude, current speed and direction (available through a mouse click over the current vector) near the raft can be used to predict the movement of the raft and a possible beaching time, in essence, forming an early warning system.

Derived Ocean Color Data with Ocean Currents
Google Earth Interpretation
A KML file is created and provides Google Earth the image and appropriate ocean current data for visualization

  SaWS Clickable Map

Dierssen, H. M., A. Chlus, and B. Russell (2015). Hyperspectral discrimination of floating mats of seagrass wrack and the macroalgae Sargassum in coastal waters of Greater Florida Bay using airborne remote sensing. Remote Sens. Environ., 167:247-258.

Feagin, R. A. and A. M. Williams (2010). Sargassum: Erosion and Biodiversity on the Beach, Spatial Sciences Laboratory, Dept. Ecosystem Science & Management, Texas A&M University, pp23.

Franks, J., D. R. Johnson, D. S. Ko, G. Sanchez-Rubio, J.R. Hendon, and M. Lay (2011), Unprecedented Influx of pelagic Sargassum along Caribbean island coastlines during summer 2011, Proc. Gulf Caribb. Fish. Inst., 64:6-8.

Gower, J., C. Hu, G, Borstad, and S. King (2006), Ocean color satellites show extensive lines of floating Sargassum in the Gulf of Mexico, IEEE Trans. Geosci. Remote Sens., 44, 3619–3625.

Gower, J., E. Young, E., and S. King (2013), Satellite images suggest a new Sargassum source region in 2011, Remote Sens. Lett. 4, 764–773.

Hardy, R. F. (2014). Assessment of surface-pelagic drifting communities and behavior of early juvenile sea turtles in the Northern Gulf of Mexico. MS Thesis, University of South Florida, 118pp.

Hu, C (2009), A novel ocean color index to detect floating algae in the global oceans, Remote Sens. Environ., 113, 2118–2129.

Hu, C., B. B. Barnes, B. Murch, and P. Carlson (2014), Satellite-based virtual buoy system (VBS) to monitor coastal water quality, Optical Engineering, 53, 051402. doi: 10.1117/1.OE.53.5.051402.

Hu, C., L. Feng, R.F. Hardy, and E. J. Hochberg (2015), Spectral and spatial requirements of remote measurements of pelagic Sargassum macroalgae, Remote Sens. Environ., 167, 229-246. doi: doi:10.1016/j.rse.2015.05.022

Huffard, C. L., S. von Thun, A. D. Sherman, K. Sealey, and K. L. Smith Jr. (2014). Pelagic Sargassum community change over a 40-year period: temporal and spatial variability. Mar. Bio, 161:2735-2751

Lapointe, B. E., L. E. West, T. T. Sutton, and C. Hu (2014), Ryther revisited: nutrient excretions by fishes enhance productivity of pelagic Sargassum in the western North Atlantic Ocean, J. Exp. Mar. Bio. Ecol. 458:46-56.

Milledge, J. J., B. V. Nielsen, and D. Bailey (2015). High-value products from macroalgae: the potential uses of the invasive brown seaweed, Sargassum muticum. Reviews in Environmental Science and Bio/Technology. 15:67-88.

Parr, A.E. (1939), Quantitative observations on the pelagic Sargassum vegetation of the western North Atlantic, Bull. Bingham Oceanog. Coll., Peabody Museum of Natural History, Yale University, 6(7): 1-94.

Oceanography 28(3):8–10

Smetacek, V., and A. Zingone (2013). Green and golden seaweed tides on the rise, Nature, 504:84-88.

Webster, R. K., and T. Linton (2013), Development and implementation of Sargassum Early Advisory System (SEAS), Shore and Beach, 81(3): 1 – 6.

Wang, M., and C. Hu (2016), Mapping and quantifying Sargassum distribution and coverage in the Central West Atlantic using MODIS observations, Remote Sens. Environ., minor revision.

Witherington B., H. Shigetomo, and R. Hardy (2012), Young sea turtles of the pelagic Sargassum-dominated drift community: habitat use, population density, and threats, Mar Ecol Prog Ser 463: 1-22.