I am a research director at the national research body (CNRS). I work in a research institute devoted to the ocean and climate at the Sorbonne University, Paris, France. I studied maths and physics here in France, before incorporating an understanding of biological and biochemical processes in the ocean.
When we think of marine life, we usually think of big organisms such as fish or algae, but in fact most marine life is invisible to the naked eye, and is formed of microscopic organisms which are called phytoplankton. Phytoplankton are very important to the ocean because they are at the heart of the food web. They are eaten by larger herbivore organisms, called zooplanktons, that are eaten by small fish, themselves eaten by larger fish. So, as you can imagine, if the quantity of phytoplankton was to decrease, there would be a decrease at all levels of the food chain.
Phytoplankton are also very important for the climate because they are photosynthetic organisms, they use CO2 and organic carbon to grow. They produce oxygen like any plant on Earth.
They absorb this CO2 in the upper few meters of the ocean, where there is enough light for photosynthesis. This organic material builds their body which then degrades and sinks to the ocean floor. This creates what we call a biological carbon pump. This pump is a mechanism that enables the ocean to take carbon from the atmosphere to the bottom of the ocean and naturally regulate climate change.
What is fascinating about phytoplankton is that they are invisible to the naked eye but you can see them from satellites. The reason for this is because they are photosynthetic organisms, and therefore they have pigments, which give a certain colour to the water. Differences in the colours’ shades can be seen from satellites, which enable us to observe the quantity of phytoplankton at the ocean’s surface, in any location at any time. We have had this data for 20 years now, so we can follow how this concentration has evolved over time. In addition to ocean colour satellites such as Copernicus Sentinel, there are other satellite missions supported by CNES that enable the observation of additional variables that are important in understanding what is happening in the ocean, such as sea surface temperature, salinity at the ocean’s surface or elevation of the ocean’s surface which provides information on surface currents.
When we think of space exploration, we probably all think of the beautiful images of the surface of Mars. I am sure that most people have never seen these fantastic images of phytoplankton on our planet before. It is very important to realise that satellites can reveal a lot of what’s happening on planet Earth.
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