In early July 2019, Sentinel-3 captured images showing blooms of Sargassum seaweed, which made the headlines due to their rapid growth and how far they spread.
11 November 2020
03 July 2019
By Ben Loveday (PML) and Hayley Evers-King (EUMETSAT)
Sargassum seaweed occurs naturally in its namesake - the Sargasso Sea (Figure 1). However, recent studies using time series of satellite data (Wang et al., 2019) have found an increase in both spatial extent and density of this seaweed — stretching across the Atlantic Ocean.
Sargassum plays an important role in ocean ecosystems as a habitat for pelagic (open ocean) animals, including various species of fish and turtles.
However, when large amounts of this seaweed reach the shore, they can cause numerous problems for both people and animals. Beaches full of rotting seaweed can affect tourism, and pose a potential health issue for beachgoers (Figure 2).
Satellite ocean colour data provides images at suitable temporal and spatial scales to track Sargassum from the open ocean, to the coastal zone. Figures 3 and 4 show how Sargassum can be detected using ocean colour data from the OLCI sensor aboard Sentinel-3, in both true colour imager (Figure 3) and using specific mathematical formulae (‘algorithms’) such as those used in the aforementioned study (Figure 4).
In a project by CLS, funded by the European Space Agency, satellite data from various sensors including OLCI is being used to track the Sargassum and help local managers prepare for its impacts.
The great Atlantic Sargassum belt , Wang et al., 2019
A novel ocean color index to detect floating algae in the global oceans , Chuanmin Hu, 2009
Sargassum: The biggest seaweed bloom in the world (BBC News)
Largest Sargassum Seaweed Bloom in the World Found by NASA (Miami Times)
Other bloom cases
Swirls of cyanobacteria in the Baltic Sea
Blooms of blue-green algae were visible across the Baltic Sea in Sentinel-3 imagery during August 2019.
Internal waves in the Eastern Strait of Gibraltar
In May 2017, MODIS imagery from the Terra satellite revealed a rarely observed movement of water – internal waves or solitons in the eastern Strait of Gibraltar.
Using Sentinel-3 to monitor chlorophyll concentrations in the Black Sea
Using Sentinel-3 ocean colour data to investigate the question 'Does a light breeze influence the distribution of chlorophyll concentrations in the Black Sea?'.
Phytoplankton Blooms spotted by Sentinel-3
Sentinel-3A has captured a number of images of the variety of species of phytoplankton that bloom in the world’s oceans and lakes.
Latest case studies
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