Sakina-Dorothée Ayata, a marine ecologist and lecturer at Sorbonne University, studies the biogeography and functional diversity of marine plankton.
‘Women oceanographers’ (11/12). They have made the ocean their object of study, sometimes even their main concern.Physicists, chemists, geologists or biologists, they all contribute to improving our knowledge of the marine environment. océans connectés sets out to meet them across France.
by Marion Durand
Cover photo © Marion Durand
We meet Sakina-Dorothée Ayata one morning in April, near the Jardin des Plantes, not far from Sorbonne University where the Laboratoire d’Océanographie et du Climat : Expérimentations et Approches Numériques ( LOCEAN), which she joined in September 2021, is based. Over tea, the oceanographer and marine ecologist talks passionately about her subject of study: plankton. Animals or plants, these organisms come in all shapes and sizes, often microscopic but sometimes reaching several metres in length, floating in the currents and populating every nook and cranny of the ocean. Plankton is everywhere, even in underground caves and lakes. Sakina-Dorothée Ayata is interested in the workings of these planktonic ecosystems, their distribution and their future.
Plankton is so attractive to scientists because it plays a crucial role in climate regulation, biogeochemical cycles and the dynamics of marine food webs. “Plankton is essential to the functioning of marine food webs because it is their foundation. Almost all marine organisms feed on them and depend on them to live, explains Sakina-Dorothée Ayata. Through photosynthesis, plankton fixes carbon and plays a major role in the biological carbon pump, helping to reduce the concentration of CO2 in the atmosphere as a result of human activity”. By fixing carbon dioxide, phytoplankton also release oxygen, which enables many marine species to breathe.
Changement climatique et plancton
Climate change, rising sea temperatures, ocean acidification and changes in currents are all disruptors for planktonic ecosystems, which thrive where conditions are favourable. In 2016, Sakina-Dorothée Ayata and Fabio Benedetti studied the impact of climate change on the functional diversity of copepods, small crustaceans that dominate the biomass of zooplankton in the Mediterranean. ‘The Mediterranean is one of the seas most affected by climate change, because we know that with rising temperatures and evaporation, the water is becoming much saltier, and the conditions in these waters will change significantly because of the high surface stratification,” explains the researcher.
Planktonic larva © Sakina-Dorothée Ayata
The study, carried out by his doctoral student, reveals that by 2100, the number of copepods will have fallen sharply, but on the scale of the Mediterranean, due to the abundance and diversity of plankton, the main ecological functions will still be provided. ‘It’s reassuring, but the Mediterranean is a special case,” adds the oceanographer, who is now working on the Arctic. “There, zooplankton is characterised by the dominance of a few species that are really adapted to polar conditions, as they spend the winter dormant in the depths of the ocean. In spring, the copepods return to the surface to feed and reproduce. But the researchers have observed that these species tend to move northwards to follow their thermal referendum, i.e. the temperature that best suits them. But the ocean is warming, even at the poles. “At some point, even at the North Pole, there will no longer be any areas that are cold enough – that’s the first physical limit. The second problem is that we don’t know how these species will adapt to the polar night.
Researchers have also observed a time lag between the phytoplankton bloom and the zooplankton bloom. This time lag between the food available and the organisms is a cause for concern for the survival of certain populations. In the 1980s, natural climate variability led to a shift in the spawning and reproduction period for small zooplankton crustaceans. These were the cod’s main diet. They were replaced by a smaller species that was less interesting from a nutritional point of view, which led to a drop in cod stocks and had a major impact on fisheries.
Sakina-Dorothée Ayata’s main interest is to gain a better understanding of the link between biodiversity and the functioning of pelagic ecosystems on several spatial and temporal scales. To answer these questions, the oceanographer uses digital tools (statistics, machine learning, dynamic models) and analyses large datasets (occurrence, quantitative imaging, genomics).
Sakina-Dorothée Ayata © Marion Durand
” I’m no longer flying “
What can we do to save plankton? “The best way to act is to drastically reduce our greenhouse gas emissions. We’ve known for a long time that these emissions have an impact on plankton ecosystems, but also on our lives,’ replies Sakina-Dorothée Ayata. This requires us to make some major societal choices. We need to think not in terms of five or ten years, but in terms of 25 or 50 years.
While society is increasingly aware of the impact of climate change on ecosystems, for Sakina-Dorothée Ayata, ‘the message is struggling to get through to political decision-makers’.
“We’re all concerned about reducing greenhouse gas emissions. Personally, I don’t fly any more! I used to go to conferences and travel a lot in Europe and the United States’, she confides. Now she opts for video-conferencing meetings or travels by train when the destination allows. “My individual reflection is part of a more global awareness. Not all scientists are aware of this, far from it, but some are making strong choices, such as not flying or redirecting their research to deal with the more urgent issues of climate change’.
Its laboratory is one of the first to examine the carbon footprint of research. This commitment is part of the national initiative led by the Labos1point5 collective, which aims to better understand and reduce the impact of scientific research activities on the environment, and in particular on the climate.
Sakina during a mediation workshop at the Centre Hospitalier Universitaire de Brest. Credit: Sakina-Dorothée Ayata
A podcast on a web radio
In 2023, Sakina-Dorothée Ayata was awarded a chair in scientific mediation at the Institut Universitaire de France for the ZOOTRAIT project, on the diversity of the mésozooplancton marin.
These numerous projects were also possible because she benefited from several reductions in her teaching time as a teacher-researcher. But she has continued to teach a few courses at Sorbonne University. I wanted to be a teacher-researcher even before choosing my speciality’, recalls the oceanographer, who is very involved in scientific outreach.
For the past three years, she has hosted the podcast Plonger dans les océans on the webradio EU radio. The wide-ranging episodes cover everything from her life as a researcher to issues such as underwater mineral extraction and overfishing.
Sakina-Dorothée Ayata also works in many schools, from nursery to high school, to raise awareness among the very young of the need to protect the oceans and the beauty of marine life. “We teach toddlers about farm animals and circus animals. Why not talk about the ocean? From the start of the new school year, the ecologist will be taking part in workshops on plankton in nursery classes in the Paris region. “I want to show these children that there’s more to life than their everyday lives, to make them dream and encourage their curiosity and imagination.
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