Phenotypic plasticity of oysters to ocean acidification in temperate and tropical environments

La plasticité phénotypique est la première ligne de défense des espèces face aux changements globaux, tamponnant leur impact sur la fitness individuelle. Toutefois, cet effet tampon est limité par un point de bascule au-delà duquel les espèces devront s’adapter ou disparaître. Ces points de bascule sont déterminés en modélisant les normes de réaction des traits phénotypiques sur une large gamme de variations environnementales. Cette approche reste anecdotique dans l’étude des effets de l’acidification des océans (AO) sur les organismes marins. En conséquence, les points de bascule restent méconnus chez l’huître creuse et l’huître perlière dont le déclin aurait un impact économique et écologique majeur. Ce travail de thèse établit les premières normes de réaction holistiques, à l’échelle macro-physiologique (taux physiologiques, paramètres de la coquille) et moléculaire (transcriptomique, lipidomique), d’organismes exposés à une vaste gamme de pH en milieux tempéré et tropical. De cette manière, nous avons identifié un seuil de tolérance à pH 7.3-6.9 en dessous duquel la fitness des juvéniles d’huître creuse et d’huître perlière est impactée. Une exposition à court-terme à des pH excédant les points de bascules aura un impact à long-terme sur la fitness de l’huître creuse qui ne peut notamment pas compenser le retard de croissance subi. Le seuil de tolérance à l’AO est déjà atteint aujourd’hui dans le milieu de vie de l’huître creuse lors d’évènements extrêmes d’acidification, qui devraient s’accentuer dans le futur menaçant les populations sauvages et aquacoles. Les conditions actuelles de pH rencontrées par l’huître perlière restent méconnues requérant la mise en place d’un suivi du pH à large échelle afin de pouvoir conclure sur le futur de l’espèce.Phenotypic plasticity is the first defense of organisms against global changes, buffering their impact on individual fitness. However, this buffering capacity is limited by the tipping point beyond which species will have to adapt or disappear. These tipping points are determined by modeling the reaction norms for phenotypic traits over a wide range of environmental conditions. This approach is used anecdotally to study the impacts of ocean acidification (OA) on marine organisms. Therefore, tipping points remain unknown for the Pacific oyster and the pearl oyster whose population decline would have a great economic an environmental impact. This thesis work establishes the first holistic reactions norms, at macrophysiological (physiological rates, shell parameters) and molecular scales (transcriptomic, lipidomic), in organisms exposed to a wide range of pH in temperate and tropical environments.Thus, we identified a tolerance threshold at pH 7.3-6.9 below which the fitness of Pacific oyster and that of pearl oyster are impacted. Short-term exposure to pH below the tipping points will have a long-term impact on the Pacific oyster which will not be able to compensate for growth stunting. The tolerance threshold to OA is already reached in habitats of the Pacific oyster during extreme acidification events which must increase in the future, threatening natural and farmed populations. The ambient pH conditions encountered by pearl oysters remain unknown, requiring the establishment of large-scale pH monitoring in order to conclude on the future of the species

Plasticité phénotypique des huîtres à l'acidification des océans en milieux tempéré et tropical

Phenotypic plasticity is the first defense of organisms against global changes, buffering their impact on individual fitness. However, this buffering capacity is limited by the tipping point beyond which species will have to adapt or disappear. These tipping points are determined by modeling the reaction norms for phenotypic traits over a wide range of environmental conditions. This approach is used anecdotally to study the impacts of ocean acidification (OA) on marine organisms. Therefore, tipping points remain unknown for the Pacific oyster and the pearl oyster whose population decline would have a great economic an environmental impact. This thesis work establishes the first holistic reactions norms, at macrophysiological (physiological rates, shell parameters) and molecular scales (transcriptomic, lipidomic), in organisms exposed to a wide range of pH in temperate and tropical environments.Thus, we identified a tolerance threshold at pH 7.3-6.9 below which the fitness of Pacific oyster and that of pearl oyster are impacted. Short-term exposure to pH below the tipping points will have a long-term impact on the Pacific oyster which will not be able to compensate for growth stunting. The tolerance threshold to OA is already reached in habitats of the Pacific oyster during extreme acidification events which must increase in the future, threatening natural and farmed populations. The ambient pH conditions encountered by pearl oysters remain unknown, requiring the establishment of large-scale pH monitoring in order to conclude on the future of the species.La plasticité phénotypique est la première ligne de défense des espèces face aux changements globaux, tamponnant leur impact sur la fitness individuelle. Toutefois, cet effet tampon est limité par un point de bascule au-delà duquel les espèces devront s’adapter ou disparaître. Ces points de bascule sont déterminés en modélisant les normes de réaction des traits phénotypiques sur une large gamme de variations environnementales. Cette approche reste anecdotique dans l’étude des effets de l’acidification des océans (AO) sur les organismes marins. En conséquence, les points de bascule restent méconnus chez l’huître creuse et l’huître perlière dont le déclin aurait un impact économique et écologique majeur. Ce travail de thèse établit les premières normes de réaction holistiques, à l’échelle macro-physiologique (taux physiologiques, paramètres de la coquille) et moléculaire (transcriptomique, lipidomique), d’organismes exposés à une vaste gamme de pH en milieux tempéré et tropical. De cette manière, nous avons identifié un seuil de tolérance à pH 7.3-6.9 en dessous duquel la fitness des juvéniles d’huître creuse et d’huître perlière est impactée. Une exposition à court-terme à des pH excédant les points de bascules aura un impact à long-terme sur la fitness de l’huître creuse qui ne peut notamment pas compenser le retard de croissance subi. Le seuil de tolérance à l’AO est déjà atteint aujourd’hui dans le milieu de vie de l’huître creuse lors d’évènements extrêmes d’acidification, qui devraient s’accentuer dans le futur menaçant les populations sauvages et aquacoles. Les conditions actuelles de pH rencontrées par l’huître perlière restent méconnues requérant la mise en place d’un suivi du pH à large échelle afin de pouvoir conclure sur le futur de l’espèce

Plasticité phénotypique des huîtres à l'acidification des océans en milieux tempéré et tropical

Phenotypic plasticity is the first defense of organisms against global changes, buffering their impact on individual fitness. However, this buffering capacity is limited by the tipping point beyond which species will have to adapt or disappear. These tipping points are determined by modeling the reaction norms for phenotypic traits over a wide range of environmental conditions. This approach is used anecdotally to study the impacts of ocean acidification (OA) on marine organisms. Therefore, tipping points remain unknown for the Pacific oyster and the pearl oyster whose population decline would have a great economic an environmental impact. This thesis work establishes the first holistic reactions norms, at macrophysiological (physiological rates, shell parameters) and molecular scales (transcriptomic, lipidomic), in organisms exposed to a wide range of pH in temperate and tropical environments.Thus, we identified a tolerance threshold at pH 7.3-6.9 below which the fitness of Pacific oyster and that of pearl oyster are impacted. Short-term exposure to pH below the tipping points will have a long-term impact on the Pacific oyster which will not be able to compensate for growth stunting. The tolerance threshold to OA is already reached in habitats of the Pacific oyster during extreme acidification events which must increase in the future, threatening natural and farmed populations. The ambient pH conditions encountered by pearl oysters remain unknown, requiring the establishment of large-scale pH monitoring in order to conclude on the future of the species.La plasticité phénotypique est la première ligne de défense des espèces face aux changements globaux, tamponnant leur impact sur la fitness individuelle. Toutefois, cet effet tampon est limité par un point de bascule au-delà duquel les espèces devront s’adapter ou disparaître. Ces points de bascule sont déterminés en modélisant les normes de réaction des traits phénotypiques sur une large gamme de variations environnementales. Cette approche reste anecdotique dans l’étude des effets de l’acidification des océans (AO) sur les organismes marins. En conséquence, les points de bascule restent méconnus chez l’huître creuse et l’huître perlière dont le déclin aurait un impact économique et écologique majeur. Ce travail de thèse établit les premières normes de réaction holistiques, à l’échelle macro-physiologique (taux physiologiques, paramètres de la coquille) et moléculaire (transcriptomique, lipidomique), d’organismes exposés à une vaste gamme de pH en milieux tempéré et tropical. De cette manière, nous avons identifié un seuil de tolérance à pH 7.3-6.9 en dessous duquel la fitness des juvéniles d’huître creuse et d’huître perlière est impactée. Une exposition à court-terme à des pH excédant les points de bascules aura un impact à long-terme sur la fitness de l’huître creuse qui ne peut notamment pas compenser le retard de croissance subi. Le seuil de tolérance à l’AO est déjà atteint aujourd’hui dans le milieu de vie de l’huître creuse lors d’évènements extrêmes d’acidification, qui devraient s’accentuer dans le futur menaçant les populations sauvages et aquacoles. Les conditions actuelles de pH rencontrées par l’huître perlière restent méconnues requérant la mise en place d’un suivi du pH à large échelle afin de pouvoir conclure sur le futur de l’espèce

Plasticité phénotypique des huîtres à l'acidification des océans en milieux tempéré et tropical

Phenotypic plasticity is the first defense of organisms against global changes, buffering their impact on individual fitness. However, this buffering capacity is limited by the tipping point beyond which species will have to adapt or disappear. These tipping points are determined by modeling the reaction norms for phenotypic traits over a wide range of environmental conditions. This approach is used anecdotally to study the impacts of ocean acidification (OA) on marine organisms. Therefore, tipping points remain unknown for the Pacific oyster and the pearl oyster whose population decline would have a great economic an environmental impact. This thesis work establishes the first holistic reactions norms, at macrophysiological (physiological rates, shell parameters) and molecular scales (transcriptomic, lipidomic), in organisms exposed to a wide range of pH in temperate and tropical environments.Thus, we identified a tolerance threshold at pH 7.3-6.9 below which the fitness of Pacific oyster and that of pearl oyster are impacted. Short-term exposure to pH below the tipping points will have a long-term impact on the Pacific oyster which will not be able to compensate for growth stunting. The tolerance threshold to OA is already reached in habitats of the Pacific oyster during extreme acidification events which must increase in the future, threatening natural and farmed populations. The ambient pH conditions encountered by pearl oysters remain unknown, requiring the establishment of large-scale pH monitoring in order to conclude on the future of the species.La plasticité phénotypique est la première ligne de défense des espèces face aux changements globaux, tamponnant leur impact sur la fitness individuelle. Toutefois, cet effet tampon est limité par un point de bascule au-delà duquel les espèces devront s’adapter ou disparaître. Ces points de bascule sont déterminés en modélisant les normes de réaction des traits phénotypiques sur une large gamme de variations environnementales. Cette approche reste anecdotique dans l’étude des effets de l’acidification des océans (AO) sur les organismes marins. En conséquence, les points de bascule restent méconnus chez l’huître creuse et l’huître perlière dont le déclin aurait un impact économique et écologique majeur. Ce travail de thèse établit les premières normes de réaction holistiques, à l’échelle macro-physiologique (taux physiologiques, paramètres de la coquille) et moléculaire (transcriptomique, lipidomique), d’organismes exposés à une vaste gamme de pH en milieux tempéré et tropical. De cette manière, nous avons identifié un seuil de tolérance à pH 7.3-6.9 en dessous duquel la fitness des juvéniles d’huître creuse et d’huître perlière est impactée. Une exposition à court-terme à des pH excédant les points de bascules aura un impact à long-terme sur la fitness de l’huître creuse qui ne peut notamment pas compenser le retard de croissance subi. Le seuil de tolérance à l’AO est déjà atteint aujourd’hui dans le milieu de vie de l’huître creuse lors d’évènements extrêmes d’acidification, qui devraient s’accentuer dans le futur menaçant les populations sauvages et aquacoles. Les conditions actuelles de pH rencontrées par l’huître perlière restent méconnues requérant la mise en place d’un suivi du pH à large échelle afin de pouvoir conclure sur le futur de l’espèce

Plasticité phénotypique des huîtres à l'acidification des océans en milieux tempéré et tropical

Phenotypic plasticity is the first defense of organisms against global changes, buffering their impact on individual fitness. However, this buffering capacity is limited by the tipping point beyond which species will have to adapt or disappear. These tipping points are determined by modeling the reaction norms for phenotypic traits over a wide range of environmental conditions. This approach is used anecdotally to study the impacts of ocean acidification (OA) on marine organisms. Therefore, tipping points remain unknown for the Pacific oyster and the pearl oyster whose population decline would have a great economic an environmental impact. This thesis work establishes the first holistic reactions norms, at macrophysiological (physiological rates, shell parameters) and molecular scales (transcriptomic, lipidomic), in organisms exposed to a wide range of pH in temperate and tropical environments.Thus, we identified a tolerance threshold at pH 7.3-6.9 below which the fitness of Pacific oyster and that of pearl oyster are impacted. Short-term exposure to pH below the tipping points will have a long-term impact on the Pacific oyster which will not be able to compensate for growth stunting. The tolerance threshold to OA is already reached in habitats of the Pacific oyster during extreme acidification events which must increase in the future, threatening natural and farmed populations. The ambient pH conditions encountered by pearl oysters remain unknown, requiring the establishment of large-scale pH monitoring in order to conclude on the future of the species.La plasticité phénotypique est la première ligne de défense des espèces face aux changements globaux, tamponnant leur impact sur la fitness individuelle. Toutefois, cet effet tampon est limité par un point de bascule au-delà duquel les espèces devront s’adapter ou disparaître. Ces points de bascule sont déterminés en modélisant les normes de réaction des traits phénotypiques sur une large gamme de variations environnementales. Cette approche reste anecdotique dans l’étude des effets de l’acidification des océans (AO) sur les organismes marins. En conséquence, les points de bascule restent méconnus chez l’huître creuse et l’huître perlière dont le déclin aurait un impact économique et écologique majeur. Ce travail de thèse établit les premières normes de réaction holistiques, à l’échelle macro-physiologique (taux physiologiques, paramètres de la coquille) et moléculaire (transcriptomique, lipidomique), d’organismes exposés à une vaste gamme de pH en milieux tempéré et tropical. De cette manière, nous avons identifié un seuil de tolérance à pH 7.3-6.9 en dessous duquel la fitness des juvéniles d’huître creuse et d’huître perlière est impactée. Une exposition à court-terme à des pH excédant les points de bascules aura un impact à long-terme sur la fitness de l’huître creuse qui ne peut notamment pas compenser le retard de croissance subi. Le seuil de tolérance à l’AO est déjà atteint aujourd’hui dans le milieu de vie de l’huître creuse lors d’évènements extrêmes d’acidification, qui devraient s’accentuer dans le futur menaçant les populations sauvages et aquacoles. Les conditions actuelles de pH rencontrées par l’huître perlière restent méconnues requérant la mise en place d’un suivi du pH à large échelle afin de pouvoir conclure sur le futur de l’espèce

Pacific oysters do not compensate growth retardation following extreme acidification events

International audienceOcean acidification caused by anthropogenic carbon dioxide emissions alters the growth of marine calcifiers. Although the immediate effects of acidification from global ocean models have been well studied on calcifiers, their recovery capacity over a wide range of pH has never been evaluated. This aspect is crucial because acidification events that arise in coastal areas can far exceed global ocean predictions. However, such acidification events could occur transiently, allowing for recovery periods during which the effects on growth would be compensated, maintained or amplified. Here we evaluated the recovery capacity of a model calcifier, the Pacific oyster Crassostrea gigas . We exposed juveniles to 15 pH conditions between 6.4 and 7.8 for 14 days. Oyster growth was retarded below pH 7.1 while shells were corroded at pH 6.5. We then placed the oysters under ambient pH > 7.8 for 42 days. Growth retardation persisted at pH levels below pH 7.1 even after the stress was removed. However, despite persistent retardation, growth has resumed rapidly suggesting that the oysters can recover from extreme acidification. Yet we found that the differences in individual weight between pH conditions below 7.1 increased over time, and thus the growth retardation cannot be compensated and may affect the fitness of the bivalves

Seawater carbonate chemistry and growth retardation of Pacific oyster Crassostrea gigas

We evaluated the recovery capacity of a model calcifier, the Pacific oyster Crassostrea gigas. We exposed juveniles to 15 pH conditions between 6.4 and 7.8 for 14 days. Oyster growth was retarded below pH 7.1 while shells were corroded at pH 6.5. We then placed the oysters under ambient pH > 7.8 for 42 days. The oysters from each pH condition were briefly dried with absorbent paper and the total wet body weight was measured with a Mettler precision balance (Mettler-Toledo) during the exposure period on days 6, 10 and 14, and then during the ambient pH period on days 4, 7, 9, 11, 14, 18, 22, 28, 36 and 42

Pacific oysters do not compensate growth retardation following extreme acidification events

Ocean acidification caused by anthropogenic carbon dioxide emissions alters the growth of marine calcifiers. Although the immediate effects of acidification from global ocean models have been well studied on calcifiers, their recovery capacity over a wide range of pH has never been evaluated. This aspect is crucial because acidification events that arise in coastal areas can far exceed global ocean predictions. However, such acidification events could occur transiently, allowing for recovery periods during which the effects on growth would be compensated, maintained or amplified. Here we evaluated the recovery capacity of a model calcifier, the Pacific oyster Crassostrea gigas. We exposed juveniles to 15 pH conditions between 6.4 and 7.8 for 14 days. Oyster growth was retarded below pH 7.1 while shells were corroded at pH 6.5. We then placed the oysters under ambient pH > 7.8 for 42 days. Growth retardation persisted at pH levels below pH 7.1 even after the stress was removed. However, despite persistent retardation, growth has resumed rapidly suggesting that the oysters can recover from extreme acidification. Yet we found that the differences in individual weight between pH conditions below 7.1 increased over time, and thus the growth retardation cannot be compensated and may affect the fitness of the bivalves

Differential reaction norms to ocean acidification in two oyster species from contrasting habitats

International audienceOcean acidification (OA), a consequence of the increase in anthropogenic emissions of carbon dioxide, causes major changes in the chemistry of carbonates in the ocean with deleterious effects on calcifying organisms. The pH/PCO2 range to which species are exposed in nature is important to consider when interpreting the response of coastal organisms to OA. In this context, emerging approaches, which assess the reaction norms of organisms to a wide pH gradient, are improving our understanding of tolerance thresholds and acclimation potential to OA. In this study, we deciphered the reaction norms of two oyster species living in contrasting habitats: the intertidal oyster Crassostrea gigas and the subtidal flat oyster Ostrea edulis, which are two economically and ecologically valuable species in temperate ecosystems. Six-month-old oysters of each species were exposed in common garden tanks for 48 days to a pH gradient ranging from 7.7 to 6.4 (total scale). Both species were tolerant down to a pH of 6.6 with high plasticity in fitness-related traits such as survival and growth. However, oysters underwent remodelling of membrane fatty acids to cope with decreasing pH along with shell bleaching impairing shell integrity and consequently animal fitness. Finally, our work revealed species-specific physiological responses and highlights that intertidal C. gigas seem to have a better acclimation potential to rapid and extreme OA changes than O. edulis. Overall, our study provides important data about the phenotypic plasticity and its limits in two oyster species, which is essential for assessing the challenges posed to marine organisms by OA

Grazers increase the sensitivity of coralline algae to ocean acidification and warming

International audienceCoralline algae are expected to be adversely impacted by ocean acidification and warming. Most research on these algae has involved experiments on isolated species, without considering species interactions, such as grazing. This myopic view is challenging because the impact of climate change on coralline algae will depend on the direct impacts on individual coralline species and the indirect effects of altered interactions with other species. Here, we tested the influence of grazing on the response of the coralline alga Lithothamnion corallioides to near-future ocean acidification and warming. Two three-month experiments were performed in the winter and summer seasons in mesocosms under crossed conditions of pCO(2) (ambient and high pCO(2)) and temperature (ambient and +3 degrees C) in the presence and absence of grazers. In the winter, L. corallioides photosynthesis decreased with rising temperature in the presence of grazers, while calcification increased. It is likely that increased calcification may act as a structural protection to prevent damage from grazing. However, increasing calcification rates in the presence of grazers may be detrimental to other physiological processes, such as photosynthesis. In the summer, L. corallioides primary production, respiration, and calcification were higher in the presence of grazers than in their absence. Light calcification rates were reduced under high pCO(2) in the presence of grazers only. Moreover, dark calcification rates were more adversely affected by pCO(2) increase in the presence of grazers. Through their feeding activity, grazers may alter the structural integrity of thalli and increase the sensitivity of coralline algae to ocean acidification. Our results indicate that both season and grazing play a key role in the response of L. corallioides to acidification and warming. Seasonal variations and species interactions are thus critical to consider to make ecologically relevant predictions of the effects of future environmental changes