Using satellites, I study the colour of oceans to protect marine life.

Marina Lévy, Oceanographer
Institut de Recherche pour le Développement, Paris, France

Phytoplankton are important for the climate and for ocean life. They are fascinating microscopic organisms, invisible to the naked eye, but visible from Space. A reduction in the quantities of phytoplankton would lead to a reduction in the ocean’s resources and its capacity to capture carbon dioxide, one of the causes of the greenhouse effect.

Interview

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.

Algal bloom swirls, Baltic sea, Copernicus Sentinel-2 mission Plankton has a major influence on the amount of carbon in the atmosphere and are sensitive to environmental changes. Satellites are able to monitor them for future climate change models. — Photo: ESA

Gallery

Ocean life in the Great Barrier Reef includes fish, coral and birds. Experts are very concerned about the capacity for reef survival under the increased frequency of global warming events.

Some algae species are toxic or harmful. Early warnings of harmful blooms from satellites can help to prevent fish farmers from losing their stock.

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Plankton are a major influence on the amount of carbon in the atmosphere and are sensitive to environmental changes. Satellites are able to monitor them for future climate change models. Photo: ESA

Ocean life in the Great Barrier Reef includes fish, coral and birds. Experts are very concerned about the capacity for reef survival under the increased frequency of global warming events. Photo: ESA/EU

Algal bloom, Hokkaido Island, Japan, Copernicus Sentinel-2A mission Phytoplankton plays an important role in the food chain, but they also have an impact on the global carbon cycle by absorbing carbon dioxide. Satellites provide a global view of phytoplankton and their role in, and response to, climate change. Photo: ESA/EU

Some algae species are toxic or harmful. Early warnings of harmful blooms from satellites can help to prevent fish farmers from losing their stock. Photo: ESA/EU

The Banc d’Arguin National Park, an important site for migratory birds, has also one of the richest fishing waters in western Africa. Blooms are indicators of the health of a marine ecosystem, and their monitoring is a key component of effective management of coastal and oceanic resources. Photo: Union, Copernicus Sentinel-3 imagery

Copernicus Sentinel-2 mission Photo: ESA/ATG medialab

This story is under the SDGLife below water

Conserve and sustainably use the oceans, seas and marine resources for sustainable development

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