Career

My passion for marine biology dates back to my childhood when I spent most of my summer holidays looking at biodiversity in intertidal pools. From junior high school, I knew that my career would revolve around academic research in oceanology. I did my best to reach this goal and started my university studies at the University of Rennes 1 (Rennes, France) and then later at the University of Western Brittany (Brest, France) where I completed the French equivalent to Bachelor's Degree (DEUG + Licence) in Life Sciences & Biology of Organisms (1999). I later completed the French equivalent to Masters of Science (Maîtrise + DEA) in Marine Ecology (2001). My thesis dealt with assessing the potential of using shells of the Chilean scallop Argopecten purpuratus as eulerian archives of coastal environmental variability in the South Pacific Ocean (Rinconada Bay, Chile).

I subsequently registered for doctoral studies and moved for almost two years overseas (Nouméa, New Caledonia) to work at the Institut de Recherche pour le Développement (IRD) on biology, sclerochronology and sclerochemistry of another scallop species, Comptopallium radula. The primary goal was to check if these shells could be good archives of environmental pollution by heavy metals released in the south-west lagoon by ore mining industries and urban development. I defended my Ph.D. in 2005 at the University of Western Brittany. After my doctoral thesis, I have worked for a few months as a research assistant at the European Institute for Marine Studies (IUEM, Brest, France) on a project dealing with the understanding of some geochemical signals (barium and molybdenum concentrations) archived in bivalve mollusk shells (2006).

Then, I felt a desire to work on something different and in 2007, I had the good luck to be invited by Dr. James Cloern from Water Resources Division at U.S. Geological Survey (Menlo Park, CA, USA) to describe primary production and assess the ecological importance of South San Francisco Bay salt ponds for resident and migratory birds. Nothing to do with shells but a nice ecological study on wetland dynamics!

I moved back to Europe during summer 2007 to work as a sclero-scientist with Prof. Bernd Schöne at the University of Mainz, Germany (thanks to a research grant awarded by the Alexander von Humboldt Foundation), on geochemical composition of freshwater (Anodonta cygnea, Germany) and marine (Arctica islandica, Iceland) bivalve shells. I came back to Brest at the end of 2008 for a Teaching and Research Assistant position (A.T.E.R.) during which I worked on structure and functioning of a remote Mauritanian ecosystem (Banc d'Arguin National Park), and sclerochemistry of intertidal bivalve mollusk shells Anadara senilis.

I finally got a permanent Associate Professor position at University of Western Brittany in September 2009. Since then, I teach zoology, biology of populations and ecosystems, marine ecology, and sclerochronology to undergraduate and graduate students, whereas my research at the Laboratoire des Sciences de l'Environnement Marin (LEMAR) currently deals with assessment of anthropogenic and climatic influences on structure and functioning of coastal ecosystems, and especially on phytoplankton dynamics, through geochemical records in mollusk shells from polar, temperate and tropical settings.


Research

The core of my research activities deal with extracting, analyzing and understanding structural (variation of growth increment width) and geochemical (variation of stable isotope ratios and elemental concentrations) proxies archived in shells of freshwater and marine mollusks in order (i) to get information on their life-history traits (growth, longevity, metabolism, reproduction), and (ii) to assess past and present variability of environmental conditions (temperature, salinity, primary production, pollutions, etc.). This scientific field is called sclerochronology, the aquatic equivalent to dendrochronology (study of tree rings). By extension, sclerochemistry is the sub-discipline of sclerochronology dealing with microchemical analyses performed in these biogenic structures.

Mollusk shells are formed by periodic accretion of calcium carbonate crystals (laid down in an organic matrix representing a few percents of the shell weight) at the ventral margin of bivalves and at the peristomial margin of gastropods. In many species, this results in the formation of shell growth increments (corresponding to periods of calcification) separated by growth lines (periods of growth slowdown or cessation). These internal and/or external growth lines reflect annual, monthly, fortnightly, tidal, daily and subdaily rhythms entrained by endogenous oscillators synchronized by environmental cues acting as zeitgebers (time-giver).

Pecten maximus
(A) Upper surface of the left valve of Pecten maximus (Bay of Brest, France). W1-W4 correspond to winter marks deposited during spring growth restart. (B) External daily growth increments can be observed without any treatment aside from surface cleaning.

These growth lines can then be used as chronological landmarks that provide the basis for assigning precise calendar dates to each successive increment of accreted shell material. Because most mollusks form distinct daily growth lines and grow very fast (tens to hundreds of µm d-1), they give information on high-frequency variations of (palaeo-)environmental conditions. On another hand, corals and sclerosponges are other widely used biogenic archives that provide useful data on past ecological variability at a seasonal time scale, at most, but that are not suited to reconstruction of processes occurring on short ecological time scales, ranging from days to weeks, such as phytoplankton dynamics. Another advantage of mollusks, and especially bivalves, is that some species are extremely long-lived. For instance, the ocean quahog Arctica islandica can live more than 400 years, a record of longevity for non-colonial animals! Dog cockles Glycymeris glycymeris live up to 200 years, as do freshwater mussels Margaritifera margaritifera. Therefore, in addition to high-resolution palaeoenvironmental reconstruction, bivalve shells can provide very long records of past climatic and environmental variability.

Glycymeris glycymeris
(A) 240-µm thick cross section of a dog cockle shell (Glycymeris glycymeris, Brittany, France) used for sclerochronological analyses, observed under transmitted light. (B) 900-µm thick cross section of the same specimen, used for isotopic analyses and observed under reflected light. Each hole represents one aragonite sample micromilled for stable isotope analysis.

In the past ten years, I have worked on analyzing the rhythm of formation of growth lines of some species with an in situ marking technique, using the calcein fluorochrome. To minimize stress caused by excessive handling, in situ benthic chambers were used for marking experiments. This has been made possible thanks to my qualification as a certified scientific diver (30 m water depth). I have also worked on stable isotope ratios (oxygen and carbon) and trace element concentrations (Mg/Ca, Sr/Ca, Ba/Ca, Mo/Ca, Li/Ca, heavy metals) in many species (scallops, cockles, quahogs, clams, gastropods) from different biogeographic settings (tropical: New Caledonia, Mauritania, Mexico, Florida; temperate: Brittany, Germany, Chile; sub-polar and polar: Canadian Arctic Archipelago, Iceland, and Spitzberg). Most of my work focuses on empirical and experimental calibration of these geochemical proxies (ie. to determine which environmental variable controls incorporation of such and such element or isotope in the shell). Another part of these underwater experiments is devoted to improvement of our knowledge on metabolism of these mollusks (ie. respiration and calcification rates). This is done underwater by enclosing live animals under benthic chambers connected (i) to a pump allowing water circulation, and (ii) to a multi-parameter probe continuously measuring temperature, salinity, and oxygen concentration. Repeated incubations over 24-h cycles allow identification of periods of high calcification and respiration rates, which in turn help us to interpret our proxies in the carbonated matrix. I've been involved in a similar experiment (focusing on macroalgae metabolism instead of mollusks) in April 2014, in the framework of a program aiming at understanding the origin, transformation and fate of mercury in the Lake Titicaca ecosystem (Bolivia). I'm also moving back in the past through the use of these calibrated proxies for palaeoenvironmental reconstructions using long-lived species (dog cockles and freshwater pearl mussels), especially in the framework of a EU-funded program (ARAMACC: http://aramacc.com).

Calcein marking under benthic chamber
Calcein marking of scallops (Comptopallium radula) in the south-west lagoon of New Caledonia.

Metabolism measurements of Strombus gigas in benthic chambers
Measurement of Strombus gigas metabolism using benthic chambers (Xel-Ha lagoon, Yucatan Peninsula, Mexico).

Diving in Mexico

Diving in Mexico
Diving in Mexico... Field trip in Yucatan to improve our knowldege of the biology (diet, respiration) and behaviour (migration patterns) of Strombus gigas, and to use their shells as high-resolution archives of temperature, salinity, primary production, pollution, and groundwater sources.

Diving at 79°N
The northernmost dive I've ever done... 79°N (Kongsfjord, Svalbard) - Sclerochronology and metabolism of Arctic scallops (Chlamys islandica).

More recently, I had the chance to work in Antarctica for 2 months (Adélie Land, French station Dumont d'Urville). The main goals of this expedition were to investigate recruitment of benthic invertebrates, to identify trophic relationships between major invertebrate species and primary food sources, to get insights about the behaviour of the Antarctic scallop Adamussium colbecki using accelerometry and last but not least, to use shells of the bivalve Laternula elliptica as biogenic archive of past environmental conditions. This scientific expedition was coupled to several educational projects with 4-16 yr old pupils. A website/blog was specifically created to follow this mission.

Diving in Antarctica

Diving in Antarctica

Diving in Antarctica

Diving in Antarctica
The southernmost dives I've ever done... 66°S, under sea ice (Adelie Land, Antarctica).


Scientific production

Peer-reviewed publications



Reviews

I served as a reviewer for the following journals:


Ph.D. thesis


Contributions to international conferences


Teaching

My first teaching opportunity was offered by Prof. Schöne in 2007. He proposed me to give lectures in his course Einführung in die Paläontologie (standing for Introduction to Paleontology). Most of these undergraduate students had a geosciences background. To open their minds to new ideas, I created a course related to paleontology, but with chips of marine ecology: Carbon cycle and paleoproductivity: Influence of phytoplankton on climate. The very positive feedbacks from these students, who didn't know before what was phytoplankton, convinced me of the validity of a multidisciplinary approach in teaching.

The pleasure I took in preparing and giving this lecture incited me to follow up on this track and I applied for assistant (2008-2009) and then permanent associate professor positions (since 2009) at the University of Western Brittany. Since then, I teach zoology to undergraduate students, focusing my lectures on developmental biology and entomology. I also give lectures to students in their 2nd year of B.Sc. in order to introduce them to marine ecology (general overview of the marine realm, interactions between marine organisms, main marine ecosystems, impact of oil spills). My lectures in biology of populations are focused on evolutionary biology (selection and evolution of life history traits) and conservation biology.

Although an important part of my teaching activity takes place in lecture halls, I also feel field excursions are essential to be closer to students and to show them a less boring side of university studies! So I spend some time with students in the field, especially for assessment of river biological quality through the use of macroinvertebrate communities (mostly insect larvae). In the future, I would like to organize longer field trips (a week or so) devoted to different aspects of zoology and ecology (marine diversity, botany, ornithology, etc.).

One of my favorite course is the one I give to graduate students (2nd year of M.Sc.) on Biological Records of Environment. With good colleagues, we introduce them to sclerochronology and sclerochemistry, on fish otoliths, mollusk shells, and other biogenic archives. We expose them to peer-reviewed articles on these topics, that they must read, criticize, and summarize through oral presentations with slide shows. They really like this and I feel it is the perfect way to introduce them to a future career in academic research.

The rest of my teaching activity consists in training master students (1st and 2nd year of M.Sc.) and Ph.D. students to scientific research, mostly in sclerochronology and chemistry of mollusk shells.

Finally, I supervise the 1st year of the Marine and Coastal Sciences Master program (speciality Marine Biological Sciences - SBM).


Courses taught:

B.S. in Biology:

M.S. in Marine and Coastal Sciences (Master SML), speciality Marine Biological Sciences (SBM):


Student research projects:


Miscellaneous


Logbook of my scientific/educational mission in Adelie Land, Antarctica (Nov. 2015 - January 2016) : https://sites.google.com/site/terreadelie2015/home (warm thanks to Nolwenn Coïc for the creation and maintenance of this website !)