Responses to emerging pollutants and multi-stress

LEMAR has a strong research potential in ecotoxicology, within the Brest area, in the framework of collaborations supported with CEDRE and ANSES, and at the national level, with its active participation in the Network in Aquatic Ecotoxicology, and its animation of the GDR PHYCOTOX. We will therefore clearly develop our approaches in ecotoxicology, considering the impact on marine organisms of emerging pollutants (micro and nano plastics), toxic micro-algae, but also the effects of diffuse pollution and multi-stress (chemical stress , thermal, hypoxic) on natural populations in coastal areas. Our approach aims to integrate the new “omics” approaches into ecotoxicology, with the bioenergetics and fitness of organisms. We thus fully subscribe to the exploration of the response of populations to multi-stress, within the conceptual framework of “energy-limited stress tolerance”. (Sokolova et al 2012, 2013). Other works at the interface between ecology, fishery resources and health are developing through the study of the accumulation of heavy metals in organisms.

Retrospective approach to marine ecosystems

The study of the structural and geochemical information archived in the carbonated structures of many marine organisms (bivalve shells, fish otoliths, rhodoliths, and hence the coccoliths) has undoubtedly been one of the points of interest for some fifteen years. strong and one of the specificities of LEMAR. This work highlights the considerable potential of these biogenic archives as witnesses to the current and past functioning of marine ecosystems. In recent years, LEMAR has focused on calibrating new proxies, including phytoplankton dynamics through bivalve shells (Li / Ca, Mo / Ca, Ba / Ca) or ocean acidification and climate change. with coccoliths (Li / Mg, B / Ca, δ11B), studies marked by the publication of pioneering articles in this field. It will be necessary to understand the biogeochemical mechanisms controlling the incorporation of certain tracers, and potentially new proxies, in these carbonated archives. This mechanistic approach will necessarily involve the implementation of experiments under controlled conditions (now made possible by the integration of Ifremer’s PFOM unit in 2012 and thanks to our methodological developments that make it possible to experimentally reproduce physicochemical forcings. under conditions that are representative of the natural environment), the establishment of a very high-frequency observatory of environmental conditions in Brest Bay, but also a modeling approach to the incorporation of trace elements and stable isotopes into these carbonated archives (eg DEB type models).

New methodologies for observing the coastal marine environment

New methodologies for observing coastal marine environments are being developed. Among them is underwater acoustics and accelerometry, both at the individual level (ethology) and the community (ecology, observation, monitoring). This work already largely initiated in temperate environments (in Brest and Rimouski) in connection with the LIA BeBest and the partner INP Grenoble. Already conducted by the LEMAR in Brest, in the Iroise Sea, in the Arctic and in New Caledonia, research in this area has allowed us to study very precisely the metamorphosis, movements and energy that are associated, on benthic invertebrates under stressful, hypoxic, toxic or thermal stress situations. We have strong arguments that this approach, aimed at developing the use of new sensors, brings significant advances in marine ecology of subtidal environments. Passive acoustics offer the enormous advantage of being insensitive to the state of the sea and not being intrusive.

The silicon cycle is a historical LEMAR theme.

The study of the trace metals cycle is one of LEMAR’s strong themes. Improving our knowledge of the metal cycle is crucial to better understand and quantify oceanic biogeochemical cycles of major elements (C, Si, N, S) and the biological carbon pump. The analysis of trace metals and their speciation is particularly difficult because their concentrations are extremely low and their cycle is complex. LEMAR is one of the internationally recognized laboratories for the study of the trace metals cycle, notably through the use and development of advanced techniques (SF-ICP-MS in the context of PSO, FIA, voltammetry). Our expertise in both the dissolved and particulate phase will allow us to study the interactions between these two reservoirs, notably at the oceanic interfaces. These interactions are very little studied at present and yet fundamental to better understand the bioavailability of metals. This theme will strengthen our international visibility, particularly in the context of new GEOTRACES oceanographic campaigns.

Silica and the silicon cycle

This ambitious objective requires identifying and quantifying silicon sources and sinks at the interfaces and describing the internal dynamics of the cycle in different ecosystems and on a global scale. At LEMAR we are particularly interested in the roles of different silicifiers not only for the silicon cycle, but also in other major biogeochemical cycles and in the functioning of ecosystems.

The silicon cycle is a historical theme of LEMAR. Our objective is to understand the oceanic cycle of silicon and the interactions with other biogeochemical cycles such as carbon, nitrogen, phosphorus and even iron and sulphur. This ambitious objective requires identifying and quantifying silicon sources and sinks at the interfaces and describing the internal dynamics of the cycle in different ecosystems and on a global scale. We have developed a transdisciplinary approach, including chemistry, biogeochemistry, biochemistry, physiology and biology, and use several experimental and modelling tools and multi-scale approaches from laboratory experiments to better understand the processes influencing the cycle to major natural environment observation campaigns. We have recently created an international “silicon school” bringing together a consortium of universities and organizations that offer higher-level teaching and research opportunities and an online learning course (under development) on the theme “Silica: from stellar dust to the living world”. The Silica School consortium currently includes 23 marine research institutes from 11 countries and continues to grow.

Silicifiers are living organisms that take advantage of the abundance of silicon (silicon is the second most abundant element in the earth’s crust) to build silicified architectures (in biogenic silica) from silica dissolved in water (orthosilicic acid or silicates). Their biogenic silica skeletons can help improve their physical strength, protect them from predators, improve their motility or help light and nutrients penetrate cells. In the marine domain, diatoms play a key role in the food webs of the most productive coastal or ocean ecosystems, as well as in the production of oxygen on which we depend and in the transfer of CO2 from the surface to the interior of the oceans (the biological carbon pump). The physiology and biochemistry of pelagic diatoms have been studied in depth, but there are still many gaps in the mechanisms by which they can biosynthesize biogenic silica under natural conditions far from those required for glass production in industry. Their role in the biological carbon pump and more generally the link between the Si and C cycles must also be reassessed.

In addition, recent meetings between international silicon specialists initiated by LEMAR (SILICAMICS and SILICAMICS 2) have shown that silicifiers other than pelagic diatoms can no longer be neglected. We have therefore expanded our research to include benthic diatoms, ice diatoms, sponges, picocyanobacteria, and some rhizaria that contribute to the dynamics of the silicon cycle and the functioning of many ecosystems more significantly than previously thought.