Sentinel-3 data provided perspective on big blooms of coccolithophores that formed off the southern coast of the UK in late June/early July 2019.
21 February 2023
27 June 2019
By Ben Loveday (PML) and Hayley Evers-King (EUMETSAT)
Coccolithophorid species, such as Emiliana huxleyi, are a type of calcifying of plankton that bloom in the mid to high latitudes during spring and summer. Sentinel-3 ocean colour data, combined with sea surface temperature time series from the Copernicus Marine Environmental Monitoring Service (CMEMS), can observe and help to explain why these calcium carbonate lith forming plankton might form such massive blooms.
Although individual coccolithophores are tiny (Figure 1), these spectacular blooms are one of the most visible features in ocean colour images. OLCI sensors on board the Sentinel-3 satellites regularly capture these blooms (Figure 2).
As these species form calcium carbonate shells, they play an important role in the ocean (and global) carbon cycle, and may be affected by both climate change and ocean acidification.
It is, therefore, vital to understand what drives the formation of these blooms at particular times and locations and to understand how the role of coccolithophores in the ocean may change and how this might, in turn, feed back on ocean biogeochemistry and climate.
The processes influencing phytoplankton growth are complex, and include physical factors such as solar radiation and temperature, and biological factors, including physiology, competition and predation.
The aforementioned physical factors combine to influence the level of ‘stratification’ or how stable the water column is. A stable water column can allow phytoplankton, like coccolithophores, access to light that they can use to photosynthesise and grow. Work by scientists has shown that these factors can explain a large part of the variability in coccolithophore bloom formation (Raitsos et al., 2006).
Deriving an anomaly (how much a current measurement differs from a longer term average) of sea surface temperature (Figure 3) indicates that the waters that these blooms formed in, were warmer than average, and, coupled to weak winds, may have been more stratified than usual. This may help to explain why these large blooms formed when and where they did.
Coccolithophore bloom size variation in response to the regional environment of the subarctic North Atlantic , Raitsos et al., 2006
CMEMS near-real-time SST
CMEMS reprocessed SST
Other bloom cases
Blooms in the Baltic Sea
An image of algal blooms and ocean eddies were captured by Sentinel-3A in July 2016.
Phytoplankton blooms spotted by Sentinel-3
Images of the variety of species of phytoplankton that bloom in the world’s oceans and lakes in 2017 & 2018.
Phytoplankton bloom in the Bay of Biscay
Large areas of blue-green phytplankton observed within the Bay of Biscay.
South African algal blooms
Detection of harmful algal blooms in the southern Benguela, as seen by OLCI aboard Sentinel-3.
Sentinel-3 spots Sargassum seaweed
In early July 2019, Sentinel-3 captured images showing blooms of Sargassum seaweed.