From 800 km in space, you would have to squint really hard to see one of these — a micron-sized phytoplankton and its armoured shell. But when a lot of them get together, say, a few trillion or so … what you see is the image below from the European Space Agency’s Medium Resolution Imaging Spectrometer (MERIS) instrument. The sensor, carried onboard the Envisat satellite, acquired imagery of a phytoplankton bloom that occurred this summer in the north Atlantic, off the coasts of Nova Scotia and Newfoundland in Canada.
The large, aquamarine-coloured patch visible in the image is a 300 x 200 km ocean area densely populated with phytoplankton, small aquatic organisms that form the basis of the ocean’s food chain and play a key role in the global ecosystem.
These blooms — the sudden appearance of phytoplankton in massive numbers, enough to colour the ocean and be detected from orbiting sensors — are capable of being analysed now on a global scale only in the past few decades with the advent of satellite-based sensors. The MERIS instrument offers new capabilities to marine researchers interested in phytoplankton blooms and other ocean processes.
Phytoplankton blooms are a fairly common occurrence, most often found in temperate waters. A recent study from the US National Aeronautics and Space Administration and the National Oceanic and Atmospheric Administration found an overall annual decrease in phytoplankton globally, with phytoplankton levels in open waters near the equator increasing significantly, and decreasing in many areas of open water in northern oceans.
MERIS — a colourful focus
The MERIS instrument onboard ESA’s Envisat satellite was designed with phytoplankton in mind. The primary mission of MERIS, with sensors operating in 15 bands in the visible and near-infrared portion of the spectrum and ground resolutions of 300 and 1200 metres, is to measure sea colour in the oceans and in coastal areas. It’s global objective is to make a major contribution to scientific projects which seek to understand the role of the oceans and ocean productivity in the climate system through observations of water colour and furthering the ability of scientists and researchers to forecast climate changes. A secondary objective is to further understanding of atmospheric parameters associated with clouds, water vapour and aerosols in addition to land surface parameters, in particular vegetation processes.