The Mediterranean is prey to new invasive species in its coastal waters, due to changes in environmental conditions. Operational monitoring of aquatic species has become an imperative for sustainable environmental management throughout the basin. Margot Dentan is working on this at the Université Paris 1 Panthéon-Sorbonne. In her thesis, funded by the french Priority Research Programme (PPR) Ocean & Climate, she is analysing a wide variety of existing management tools to meet the requirements of the various stakeholders in the region.
by Laurie Henry and Carole Saout-Grit
In the Mediterranean, the environmental conditions of certain coastal areas are undergoing significant change as a result of ever-increasing human pressures. The impacts are particularly significant for aquatic ecosystems, and new invasive species have been observed in recent years. However, the monitoring of aquatic species is often made difficult by the lack of correspondence between the ‘good status’ indicators defined at European level and their application at local and regional levels.
Aligning levels of governance and monitoring scales
In the Mediterranean lagoons of Occitanie, Corsica and the PACA region (Provence-Alpes-Côte d’Azur), two species have been particularly closely monitored in recent years: the European eel (Anguilla anguilla), a native species in decline, and the American blue crab (Callinectes sapidus), a non-native species that is proliferating. The proliferation of the latter has been threatening fishing activities in Occitania and Corsica since 2016. However, although fishermen are directly affected, they have little involvement in the institutional management of these species, even though they could play a crucial role as local sentinels.
blue crabs caught in the Etang de Canet-Saint-Nazaire (Pyrénées-Orientales – France, april 2023)
Since the 1990s, the European Union has gradually introduced a series of environmental directives to deal with the many ecological disturbances caused by human pressures on aquatic species and habitats. The European directives on habitats, fauna and flora (DHFF*), on water (DCE**) and on the marine environment (DCSMM***) have established the concept of ‘good ecological status’ for freshwater and marine waters as an objective to be achieved, although this notion is subject to varying interpretations depending on the local players involved.
At the Université Paris 1 Panthéon-Sorbonne, Margot Dentan is examining these disparities through a geographical and socio-political approach. She seeks to understand how scientific knowledge, the local knowledge of fishermen and the demands of public policy can converge to produce data that is relevant to both the management of species and the resilience of natural environments.
Political geography of aquatic species monitoring
Margot holds a Master’s degree in Social Sciences, Territories and Development from EHESS (École des Hautes Études en Sciences Sociales) and a Master’s degree in Coastal and Marine Management from the University of Montpellier.
Since 2022, she has been a doctoral student in geography at the University of Paris 1 Panthéon-Sorbonne, attached to both the PRODIG (Pôle de Recherche pour l’Organisation et la Diffusion de l’Information Géographique) geography laboratory and the MARBEC (MARine Biodiversity Exploitation and Conservation) marine ecology laboratory at the University of Montpellier.
Her thesis focuses on the construction and spatialisation of aquatic species monitoring at the land-sea interface. Using the cases of the European eel and the American blue crab in French Mediterranean lagoons, Margot is attempting to understand how and to what extent the ‘good status’ indicators defined at European level can be used to respond to local issues of socio-ecological resilience in aquatic environments.
Margot Dentan during a participant observation as part of blue crab monitoring: characterisation of specific abundance (benthos) in the Etang de Canet-Saint-Nazaire. (Pyrénées-Orientales – France april 2023)
Her thesis is based on a critical analysis of various monitoring methods, including innovative ones such as environmental DNA****, used for early detection of species such as blue crab, while incorporating traditional monitoring methods involving local stakeholders. The research uses traditional methods of qualitative investigation in the social sciences: semi-directive interviews and observation (including participant observation). The people surveyed fall into three categories: scientists, public policy players, fishermen and their representatives. A first field survey (4 months) was carried out between April and July 2023 in Occitanie, then a second (3 months) between March and June 2024 in PACA and Corsica.
Cappéchade fishing in the Étang du Vaccarès (Bouches-du-Rhône – France, march 2024) –
Margot Dentan’s thesis is under the joint supervision of Pierre Gautreau (Université Paris 1 Panthéon Sorbonne) and Rutger De Wit (Université de Montpellier). It is funded by the PPR Ocean & Climate Priority Research Programme, co-sponsored by CNRS and Ifremer. It responds to the challenge of improving the protection and resilience of marine environments and developing new integrative management approaches, but also echoes the cross-disciplinary challenges of developing innovative observation and modelling programmes, and sharing with the public the discovery of the Ocean and the associated societal issues.
By working at the interface between several disciplines – political geography, marine ecology, environmental sociology – Margot hopes to shed light on the workings of multi-actor collaborations and the strategies they develop to meet contemporary environmental challenges. The initial conclusions of her work highlight the challenge of striking a balance between participatory local governance and the European imperatives of conservation and ecological restoration.
* European Habitats, Fauna and Flora Directive (DHFF)
Adopted on 21 May 1992, the DHFF establishes a framework for the conservation of natural habitats and wild fauna and flora. It aims to ensure the maintenance or recovery of species and habitat types that are significant for European biodiversity. Important protection sites for species and habitats are listed in this directive, and management measures must then be implemented in these areas to maintain or restore the species and habitats to a good conservation status.
** The Water Framework Directive (DCE)
Adopted in 2000, the WFD aims to protect water resources in the European Union. It requires Member States to achieve ‘good ecological status’ for fresh, coastal and groundwater by 2027. It encourages integrated management at catchment basin level, taking account of anthropogenic pressures.
*** Marine Strategy Framework Directive (DCSMM)
Adopted in 2008, the DCSMM aims to achieve ‘good environmental status’ of European marine waters by 2020. It requires Member States to monitor and manage human impacts on marine environments, including pollution, non-native species and biodiversity, in order to preserve marine ecosystems.
**** Environmental DNA (DNAe)
is an innovative method for identifying species present in a natural environment from DNA traces (scales, hairs, faeces) collected in water or soil. This non-invasive technique facilitates biodiversity inventories and the monitoring of species, particularly invasive or endangered species.
3 Questions to Margot Dentan
Why did you decide to do a PhD in marine sciences?
I wanted to do this thesis as a continuation of my dual career in the social sciences (EHESS) and in coastal and marine management (University of Montpellier). Combining fieldwork and theoretical reflection to undertake a critical analysis of environmental policies was a very stimulating prospect.
What made you want to do this thesis? ? What were your motivations?
I co-wrote my thesis topic with Rutger De Wit and Pierre Gautreau when I was doing an internship in a marine ecology laboratory (Marbec), and I was immediately motivated by the possibility of carrying out an interdisciplinary research project. I found it particularly interesting to study lagoons, which are areas at the interface between land and sea that are affected by a wide range of ecological and socio-economic issues.
How do you see your future after this thesis?
I’d like to teach social sciences at secondary school, while working as a research associate in a laboratory. While I will of course continue to pursue some of the ideas that came out of my thesis, I would especially like to help pass on critical thinking tools to future generations.
Reference : Dentan, Margot, « Monitoring aquatic species at the land-sea interface: scales and issues involved in producing multi-level information on the European eel and the American blue crab in French Mediterranean lagoons », phD thesis 2023-2026
Contact : margot.dentan@cnrs.fr