Thermal tolerance and physiological adaptation of the oyster in a changing environment

Dr Fabrice Pernet

Dr Elodie Fleury, Dr Charlotte Corporeau

Climatological studies over the last few decades have shown a rise in the temperatures usually measured in water and air, and by a rise in sea level. In this context, it appears crucial to assess the acclimatization capacities of intertidal species to local climatic conditions, and in particular to the large amplitude thermal variations they encounter between periods of immersion and exoneration. Indeed, the nature of the habitat and the foreshore height of intertidal species will determine the amplitude of the temperatures they experience when they emerge. However, populations living at their maximum thermal tolerance limit may be more vulnerable to climate change. The main objective of this thesis project is to study the life traits and acclimatization capacities of an intertidal bivalve mollusc as a function of altitude and latitude. This study focuses on the cupped oyster Crassostrea gigas. More specifically, the objectives are i) to analyze in situ with endogenous electronic sensors how the body temperature of this species varies according to the habitat, the origin of the individuals (wild vs. farmed animals), the shoreline exposure and the hydro-climatic conditions, ii) to characterize the physiological mechanisms of acclimatization (synthesis of heat shock proteins, homeoviscous adaptation of cell membranes, metabolic depression for example) in this species in relation to temporal variations in body temperature, iii) to use mechanistic modelling, from the endogenous data collected, to investigate the allocation to the different physiological functions during emergence conditions, according to bathymetric gradients. This work will be usefull to analyze the mechanisms of thermal tolerance of this bivalve mollusc during the phases of shoreline  exposure, and the consequences of endogenous temperature change on its physiological and anatomical characteristics. The evaluation of the plasticity of individuals under these conditions will be a fundamental prerequisite for making predictions on the oyster's distribution ranges in the context of climate change, and on its ability to colonize the northern European coasts.

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