On 29 April 2005, very large areas of blue-green phytplankton were observed in great swirls within the Bay of Biscay.
25 April 2022
29 April 2005
By Jochen Kerkmann (EUMETSAT)
Stretching across almost the whole Bay, the plankton reveal currents and eddies in the water. Plankton, being tiny single-celled organisms feeding off sunlight and nutrients in the water, uses chlorophyll, like plants on land, to complete this process.
It is, in fact, the chlorophyll that gives plankton its decidedly blue-green colour and which, in large-enough concentrations, helps it to stand out against the darker blue of the clear water.
For Meteosat-8 (MSG), this phenomenon is best seen during the day using the HRV channel. Since this broad-band channel (see filter function) has a significant contribution from blue light (around 0.4 micrometer), it is suitable for viewing this type of ocean feature. It appears to a much lesser extent in the VIS0.6 channel, and not at all in the VIS0.8 and NIR1.6 channels. In the Bay of Biscay, the plankton appears to be most prevalent during spring time when there are long daily periods of sunlight and suitable sea temperatures (see also Phytoplankton bloom in the Bay of Biscay , 16 May 2004).