Impacts of environmental changes

, , ,

Coastal ecosystems are characterized by high natural variability at high frequency of the main abiotic factors.

Determining the possible reactions of living communities to anthropogenic pressures (chemical and plastic contamination, global warming, eutrophication, overexploitation of living resources) that generate proven global change is a real challenge for environmental scientists. In coastal marine environments where most of the ecological productivity is concentrated, the impact of chronic pollution raises additional questions for managers of these environments and producers of fish and aquaculture resources. Some alterations (genotoxicity, immunotoxicity, reprotoxicity) lead to population effects that may compromise the maintenance of certain species in the affected environments.

The number of coastal sites in the world ocean subjected to hypoxia and even anoxia events, more or less regularly and more or less pronounced, has increased dramatically since the 1950s. Most often, these phenomena are one of the consequences of the eutrophication of coastal areas, linked to the increasingly massive supply of nutrients to these waters. The latter stimulate phytoplankton production which, by sedimentation, induces a massive consumption of dissolved Oxygen at the water-sediment interface (bacterial degradation of this influx of organic matter). When the waters are stratified (e.g. during the summer), the bottom layer is isolated and is subjected to more or less prolonged hypoxic episodes, with serious consequences on benthic biocenoses.

Faced with various environmental pressures, marine organisms present adaptive responses of a behavioural, physiological (phenotypic plasticity), ontogenic and evolutionary nature that are individually reflected in their life traits and, at the individual and population level, in spatial-temporal dynamics.

Through a combination of experimental approaches (laboratory or in situ) and field observation studies, LEMAR will conduct several types of approaches including:

  • Mechanistic approach: characterize the adaptive responses of individuals from populations from contrasting sites in terms of exposure to chronic contamination.
  • Diagnostic approach: apply phenotypic descriptors corresponding to disturbances in essential physiological systems such as energy metabolism and the immune system, which are particularly important for the survival and development of populations.

The study of the land-sea continuum

, ,

The coastal zone, at the interface between the earth system and the sea system, concentrates a set of interfaces and natural environmental gradients, generating a very strong heterogeneity at different spatio-temporal scales. Scientific questions are therefore numerous to try to better understand the nature and dynamics of physical, biological and geochemical flows and forcings, and their interactions and feedbacks (prospective SIC-INSU). Extremely dynamic and complex, this coastal zone is also the seat of many facets of global change with climate change of course, but also strong and growing anthropogenic pressures related to urban planning, land use, exploitation mineral and living resources on land and at sea. In this context, our objectives are threefold:

● develop an integrated approach to land-to-sea transfers of dissolved and particulate matter, combining observation, process studies and modeling in estuaries and coastal areas to better understand the coastal ecosystem’s response to physical, biogeochemical forcings and biological, terrestrial and oceanic (Axis 1 of Team 3);

● Anticipate the possible evolution of the coastal ecosystem in response to global change, by developing scenarios describing the response of organisms and the coastal ecosystem to the interaction of different facets of global change: climate change, change in farming practices evolution (natural or not) of invasive species (Axis 1 of team 3, strong links to develop with the AR5 of team 2), and

● to develop a transdisciplinary approach allowing the co-construction of these scenarios and their analysis with the concerned actors, with a view to decision support in the sustainable management of the coastal socio-ecosystem (links with the “Rade de Brest” axis And with the “unruly” axis, links with the other components of the IUEM).

Ocean Physics Coupling and Biology

,

The ocean dynamics is structured on scales ranging from a thousand kilometers (basin), a few meters, through the tens / hundreds of kilometers (eddies, fronts). This last scale (meso and sub mesoscale) concentrates 90% of the energy of water bodies. These intermediate and small scales are associated with ancestrophic vertical movements that play a major role in the transport of tracers (nutrient substrates), the distribution of areas of divergence / convergence of ocean currents and the heterogeneity of marine habitats (eddies, filaments). Satellite and acoustic data highlight the important impact of these scales on marine biological activity and the spatial variability of ecosystems, an impact that can be analyzed and understood through numerical modeling. Advances in computational power and observation methods make it possible to address these processes at medium and small scale, which are essential for quantifying the flow of matter and the structuring of marine food webs. The LEMAR expertise in modeling and observation (in particular active acoustics) enables the unit’s researchers to make significant progress in this cutting-edge field, in close relationship with the LabexMer (Axis 1: The ocean machine at very high resolution; Axis 2: The complexity and effectiveness of the biological carbon pump; Axis 6: Evolution of marine habitats and adaptation of populations). The three main areas of research concern:

● Plankton biodiversity at mesoscale

● Carbon export to the deep ocean

● The distribution and behavior of intermediate (zooplankton, myctophid) and higher (elephant seals) levels.