Research

My research focus

At the boundary between biogeochemistry and marine ecology, my research interests are in tracing organic matter (OM) origin, dynamics and fate in coastal systems, and more precisely how it is channeled through trophic networks. I am interested in how natural or human induced environmental changes, such as climate change or eutrophication, in basal OM quality would affects food webs, from individual to community level. Currently, my main research is focused on the blue mussel, Mytilus edulis, a key-species of coastal environments in the Baltic Sea.

Tool Box

Stable isotopes of carbon and nitrogen (δ13C, δ15N) and fatty acids biomarkers are used as organic matter tracers in a wide range of environments, especially to study trophic relationships but also to follow biogeochemical processes. I have been using both techniques since 2013 during my master thesis and stable isotopes became the core tool of my research during my Ph.D. For the past two years, I kept playing with isotopes by learning new approaches measuring δ15N on amino acids and δ13C on fatty acids (CSIA: compound specific isotope analysis) in collaboration with Center for Physical Sciences and Technology in Vilnius (Lithuania).

Together, these techniques helped me to reveal pelagic fish larvae diet [1] and to understand the relationship between particulate organic matter and bacteria [5]. I used these biomarkers, together with environmental data in numerical and statistical approaches (e.g. isotopic mixing models (MixSIAR), uni- and multivariate statistics), to reveal particulate organic matter origin and quantify its composition in coastal systems over the French littoral [2], [3], [4] or to study changes in Mytilus edulis diet and body condition over the past 25 years in the Baltic Sea [6].

IMG_9920
Fatty acid extraction, evaporation step.

Scientific projects

Environmental Changes in the Baltic Sea Ecosystem revealed by the Blue Mussel, Mytilus edulis (2018-2020) – Project leader: Agnes Karlson (Stockholm University, Baltic Sea Center).

We analyzed archive samples of Mytilus edulis from the last 25 years sampled by the Swedish National yearly monitoring program of phytobenthic community in the Baltic Sea for elemental, bulk and compound specific isotope composition. By combining blue mussel body condition, chemical compoition and isotopic niche metrics with existing biotic and abiotic datasets on phytoplankton communities and other environmental related variables, we tested specific hypotheses on Mytilus diet, condition and growth status in order to better understand blue mussels and ecosystem responses to environmental changes [6].

MOSLIT (2014-2016) – La matière Organique Particulaire dans les Systèmes LIToraux : composition, dynamique et forçages     (EC2CO – DRIL) – Project leader: Nicolas Savoye (UMR EPOC, Université de Bordeaux / CNRS).

Particulate organic matter (POM) is deeply involved in biogeochemical cycles and constitutes the base of food webs. In coastal systems, POM is a composite pool fueled by autochthonous and allochthonous sources from pelagic, benthic and continental origin, and whose relative contributions highly vary over time and space. We studied 12 systems (three littoral systems, eight embayments and semi-enclosed systems, and one estuary) distributed along the three maritime façades of France for one to eight years in order to quantify the relative contribution of organic matter sources to the surface-water POM and to assess the drivers of their spatial and temporal variability [3], [4]. We also studied the relationship between bacteria and POM focusing on 3 systems along the continent to ocean gradient [5].

 

SOMLIT (2014-2016) – Service d’Observation en Milieu LITtoral (INSU, since 1996). National leader: Nicolas Savoye (UMR EPOC, Université de Bordeaux / CNRS).

For two years I was involved in field sampling for the sites of Aquitaine (Arcachon lagoon and Gironde estuary) and in sample analysis (pH, chlorophyll a by fluorimetry, δ13CCOP, δ15NNOP). As a part of my PhD, I contributed to the database cleaning and the scientific valorisation of the work performed by the SOMLIT.

PERMALA-LIGA (2013-2015) – Perturbations et Milieux Aquatiques Littoraux Aquitains (Conseil Regional Aquitain). Project leader: Philippe Gaudin (MIRA – Université de Pau et des Pays de l’Adour).

The French Basque coast is characterized by the occurrence of a viscous TEP-like material that appears discontinuously from late winter/early spring to late summer/early fall. We used stables isotopes of cabon and nitrogen to assess POM origin and composition in this system [2].

Trophic Ecology of Leptocephali in the South-West Pacific (2013) – Collaboration between the UMR BOREA at the Museum National d’Histoire Naturelle (Tarik Meziane and Eric Feunteun) and the Japanese Teams of the AORI and Department of Aquatic Biosciences of the University of Tokyo and the Eel Science laboratory of Nihon University.

Leptocephali are pelagic larvae of Anguilliform fish that are dispersed by currents toward adult habitats. Despite an extensive literature on their morphology and distribution area, their feeding ecology is still partly unknown. One current hypothesis suggests those larvae are feeding on particulate organic matter (POM) and assimilating some specific compounds. We combined fatty acids and stables isotopes of carbon and nitrogen to investigate trophic habits of three families of leptocephali (Muraenidae, Nemichthyidae, Serrivomeridae) caught in the differents currents of the South Pacific [1].

 

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