Background researcher

"Miriam Brandt's dissertation on the incredible biodiversity of the deep oceans is all about making the invisible visible . Portrait of a researcher who gets to the bottom of things.

During her thesis, Miriam Brandt touched bottom. The very depths, up to 8,000 meters below sea level. Doctoral student blues? Not at all. In fact, it was her goal: to sample the mud that covers the seabed in order to study the incredible little creatures that inhabit the abyss. " They're an important link in the ocean food chain because they help to recycle the matter that falls from the surface," explains the young researcher, who defended her thesis in July 2020. An essential role for a remote and little-known ecosystem.

To shed light on this mysterious universe, Miriam Brandt has turned to the study of environmental DNA, extracted directly from the abyssal mud. And to wade through this sludge, you have to pull out all the stops. " We've taken samples from 330 to 8,000 meters down, and we've lowered corers or sent robots down to get a few grams of mud from the very bottom ", explains the researcher, who recalls a 35-day campaign at sea in the Pacific: " a superb experience, living on the boat with 50 researchers and 20 crew members ". Superb and intense: "when we bring up the sediment from the bottom, it goes from 4 degrees to 25 degrees in a few hours, so we have to process it quickly so that the DNA doesn't degrade: we cut the cores, take the samples, freeze them, then send them under dry ice to the laboratory in Sète to extract the DNA ".

For a few grams of mud

But how do these few grams of mud allow Miriam Brandt to know who populates the abyss? " By studying the DNA, I looked at specific genes, genes common to all living organisms, to you, to me, and to these little beasts. These are barcode genes: reading them allows us to identify the species present. Thanks to this method, by analyzing abyssal muds collected from all over the world, I've been able to make progress towards mapping the biodiversity of the deep sea."

An ambitious project that immediately appealed to Miriam Brandt when she was looking for a thesis topic. Because she knows the seabed well, and has known it since she was a child. First through diving, which she has been practicing since the age of 12, " my grandfather was a diver, it's a family thing ". Then, at the end of secondary school, she watched the documentary Deep blue, which presents the richness of marine biodiversity, and discovered " a fascinating universe, populated by animals that live there in an incredible way, without light ". Then came Claire Nouvian's book Abysses, which turned her high school desire into a certainty: " I want to work in the sea ".

A decisive encounter

A certainty that is not always easy to convert into a study project when it comes to choosing a career path. Failing to find the right path, the student enrolled in a preparatory biology course in Marseille. A good student, she passed her first year with flying colors, but was sad to see herself " moving away from the sea". To get closer to it, Miriam Brandt crossed the globe to Australia for a road trip on the island continent for a summer, where she made a decisive encounter: " a French woman whose name I can't even remember, who spoke to me over a campfire about James Cook University, where her nephew was studying marine biology ". Seduced by freedom and the oceans, Miriam Brandt was tempted to stay in Australia... " But my father wanted me to go back to France, so we made a deal: I'd go back, finish my preparatory course, and then go back to Australia ".

A good deal, since once her second year had been validated, the young girl headed for Townsville for a bachelor's degree in marine biology and chemistry. " I discovered tropical marine ecology, met people who were passionate about it and dived on the Great Barrier Reef ," recalls the Frankfurt-born German student.

But once he had completed his bachelor's degree, nostalgia for the old continent began to set in. " Either I went back then, or I didn't go back now ". It was decided: she would return to Europe. She landed in Bremen, "the city for marine science in Germany ", where she found a place in an international master's program in ecology. Her Master's 2 thesis, on symbioses between marine invertebrates and bacteria, will be written at the Max Planck Institute for Marine Microbiology.

Total crisis

" Discovering molecular biology forced me to step out of my comfort zone ", she recalls. With my background in ecology, I felt out of step with microbiology, and I was losing touch with what had always motivated me. From ecology to microbiology, I was no longer on the right scale ". So after the Master's degree, it was " a total crisis ". Miriam Brandt turned down a PhD in Bremen, and after a short detour in the tropics, she returned to Ardèche, where she grew up, and found herself giving SVT lessons in a secondary school. Then the biology bug caught up with her: " I realized that not only did I love it, but that I could also unleash this passion in others! Definitely convinced that this was where her professional future lay, Miriam Brandt set about finding a thesis in France.

So when she came across the subject "Why not the abyss? Environmental DNA for the study of deep-sea biodiversity" at the Marbec laboratory, proposed by Sophie Arnaud-Haond, Miriam Brandt was hooked. " The presence of Ifremer and numerous other institutes and research groups makes Montpellier a stronghold of marine ecology in France, which reinforced my decision to do my doctoral research at the University of Montpellier ".

The subject interests him all the more as this work is taking on a real societal dimension. " We don't know it yet, but there's a real arms race to exploit our abyssal plains! Humans are ready to bulldoze the seabed to extract minerals such as lithium, rare earths and cobalt, which are used in new technologies. So we need to know more about this biodiversity so that we can establish regulations to protect this wonderful but mysterious ecosystem.

Protecting the seabed

It was to better alert the general public to this risk that Miriam Brandt decided to take part in the Ma thèse en 180 secondes competition in 2019. If she doesn't win, Miriam Brandt has the merit of raising awareness of deep-sea mining. " For the moment, we are witnessing exploration phases, but as early as 2024, mining permits will be issued, covering areas the size of France right in the middle of the Pacific Ocean!" worries the researcher. " It's a remote and invisible environment, and these are little creatures with which we have little emotional proximity, so it's harder to raise people's awareness of this cause ," laments Miriam Brandt, who has found this to be a fundamental battle.

It's a battle she'll soon be continuing from Norway, where she'll be starting a post-doc in Bergen in August, studying the consequences of offshore oil and gas development on biodiversity. A logical continuation of an already rich career, with the sea as a common thread, and the desire to protect it as a backdrop.