Understanding the influence of climate on marine ecosystems by 2100 is now a matter of urgency, so that appropriate policies can be drawn up. Against this backdrop, Laureline Dalaut, a doctoral student in marine sciences at the University of Montpellier since 2023, will attempt to model marine ecosystems subjected to certain climatic phenomena in order to analyse their influence on marine biomass and the oceanic food chain as a whole.
by Laurie Henry and Carole Saout-Grit
Taking action to protect marine ecosystems
The ecological emergency is here: marine ecosystems are subject to strong anthropogenic and climatic pressures that threaten them. Climate variability, such as climate change but also natural variability phenomena like ENSO*, have a direct impact on marine biodiversity, with major consequences for the fishing industry, which is essential to the livelihood of many populations.
The findings are alarming, and projections point to a significant decline in marine biomass, particularly in so-called pelagic species (animals or plants that swim and float in the open sea). But questions remain: what are the impacts of interannual climate variability on marine ecosystems? How will the biomass and spatial distribution of fish evolve with climate change? What are the underlying mechanisms of the effect of climate change on communities? What are the indirect effects of climate change, in particular on the food chain as a whole?
It is now crucial to develop new numerical models capable of projecting the long-term effects of climate change on the evolution of marine ecosystems..
Understanding how marine ecosystems respond to climate change
Some existing numerical models, such as those used in the Fish-MIP** project, have led to major advances, but also raise new questions about the ecological mechanisms involved. During her thesis, Laureline Dalaut will work on one of these models, the APECOSM*** model, and will attempt to enrich it and improve its configuration in order to fill these gaps.
Using simulations covering the period from 1958 to 2100, his work will focus on two major phenomena: interannual climate variability (ENSO in particular) and global warming. The modelling of six communities of pelagic organisms, ranging from small coastal pelagics to mesopelagic organisms (located in the water column between 200 m and 1000 m depth), should make it possible to explore several extreme climate scenarios to gain a better understanding of how temperature, access to food and ocean dynamics influence the biomass of pelagic communities.
These numerical analyses, obtained using the APECOSM model, will be able to analyse the interactions between each community and see how they evolve over the medium and long term.
They will make it possible to predict fluctuations in marine populations by 2100, and to identify the main mechanisms responsible for these changes, which are constrained by long-term changes in the environment.
Funded for 3 years by the french Priority Research Programme (PPR) Ocean & Climate, as part of Challenge 1 aimed at ‘ understanding, preventing and mitigating the impacts of climate change on the oceans ’, Laureline Dalaut’s thesis will be cosupervised by Olivier Maury and Matthieu Lengaigne (UMR MARBEC, IRD).
The expected results of this work include improved projections of changes in fish stocks. The aim is to understand how climate variability impacts and will impact the structure of ecosystems, but also how this structure is likely to evolve in order to guide fisheries management and marine ecosystem conservation policies in a context of climate change.
* ENSO – El Niño Southern Oscillation is a climatic phenomenon comprising three phases: two opposing phases, ‘El Niño’ corresponding to abnormal warming of the ocean surface and ‘La Niña’ corresponding to abnormal cooling of the ocean surface; a ‘neutral’ phase in the middle of the continuum.
** Fish-MIP (Fisheries and Marine Ecosystem Model Intercomparison Project) is an international programme aimed at comparing and evaluating marine ecosystem models to better understand the impacts of climate change on fisheries and marine biodiversity. It uses climate scenarios to project changes in marine resources on a global and regional scale, integrating various ecosystem and food models. The results of Fish-MIP contribute to IPCC reports and to the development of sustainable ocean management policies.
*** APECOSM (APex Predator ECOSystem Model) was developed by Olivier Maury, a researcher at the french Institut de Recherche pour le Développement (IRD), as part of the Marine Biodiversity, Exploitation, and Conservation (MARBEC) joint research unit. The model is supported by the MARBEC research team, which works with international institutions to study the impact of climate change on marine ecosystems.
3 Questions to Laureline Dalaut
Why did you decide to do a PhD in marine sciences?
The ocean is so vast, yet we know so little about it. I’m the first. As a very committed environmentalist, I quickly realised that the ocean plays a key role in mitigating the effects of climate change, even though it is being abused by overfishing, pollution and heavy traffic. Not to mention what it is already suffering from the consequences of climate change. Doing a thesis in marine sciences is therefore an opportunity for me to learn about the ocean and its inhabitants and to contribute to its protection.
What made you want to do this thesis? What were your motivations?
The feeling that I’m taking part in something useful, something great that will benefit everyone, both humans and the rest of the living world. This thesis is also a way for me to acquire new skills, to understand the challenges posed by global warming to marine ecosystems and those that depend on them. But it’s also a way for me to get involved professionally in what was, before, mainly a personal involvement.
How do you see your future after this thesis?
There are lots of possibilities and I don’t want to close any doors for the time being. I love research and the subject of my thesis. But I also really like mediation, the idea of creating a bridge between the world of research and civil society to train a generation that will master the concepts of climate change and be able to grasp concepts that may seem complex at first glance. There are also other professions that aim to protect ecosystems, not necessarily marine ones either. For my future projects, I need to feel useful and enjoy what I’m doing.