Posts Tagged 'laboratory'

A comparative metabolomics approach detects stress-specific responses during coral bleaching in soft corals

Chronic exposure to ocean acidification and elevated sea-surface temperatures pose significant stress to marine ecosystems. This in turn necessitates costly acclimation responses in corals in both the symbiont and host, with a re-organization of cell metabolism and structure. A large-scale untargeted metabolomics approach comprising gas chromatography mass spectrometry (GC-MS) and ultra performance liquid chromatography coupled to high resolution mass spectrometry (UPLC–MS) was applied to profile the metabolite composition of the soft coral Sarcophyton ehrenbergi and its dinoflagellate symbiont. Metabolite profiling compared ambient conditions with response to simulated climate change stressors and with the sister species, S. glaucum. Among ca. 300 monitored metabolites, 13 metabolites were modulated. Incubation experiments providing four selected upregulated metabolites (alanine, GABA, nicotinic acid and proline) in the culturing water failed to subside the bleaching response at temperature-induced stress, despite their known ability to mitigate heat stress in plants or animals. Thus the results hint to metabolite accumulation (marker) during heat stress. This study provides the first detailed map of metabolic pathways transition in corals in response to different environmental stresses, accounting for the superior thermal tolerance of S ehrenbergi versus S. glaucum which can ultimately help maintain a viable symbiosis and mitigate against coral bleaching.

Continue reading ‘A comparative metabolomics approach detects stress-specific responses during coral bleaching in soft corals’

Étude en mésocosmes des impacts de l’acidification et du réchauffement sur la composition élémentaire de la biomasse planctonique et le cycle de l’azote dans l’estuaire maritime du Saint-Laurent (in French)

Les changements globaux ont le potentiel d’altérer les cycles biogéochimiques entraînant des répercussions pour tout le réseau alimentaire. Puisque l’azote est généralement l’élément limitant en milieu estuarien, une altération de son cycle pourrait influencer l’ampleur et le type de production primaire ainsi que la composition de la communauté phytoplanctonique qui l’effectue. Il en va de même pour la composition de la matière organique qui peut affecter la valeur nutritive des algues pour les consommateurs de même que l’efficacité de la pompe biologique. Actuellement, aucune étude portant sur les impacts combinés de l’acidification et du réchauffement des eaux de l’estuaire maritime du Saint-Laurent n’a été réalisée. L’objectif de ce projet de maîtrise fut d’évaluer expérimentalement, à l’aide de mésocosme, les impacts cumulés que ces changements pourraient avoir sur la dynamique des nutriments et de l’azote en particulier ainsi que sur la composition élémentaire de la matière organique. Une combinaison factorielle de six pH (7,2; 7,4; 7,6; 7,8; 8,0 et un pH sans contrôle) et de deux températures (10 et 15°C) fut employée. Les résultats de l’expérience suggèrent que les organismes responsables des processus à l’étude sont tolérants à une diminution considérable du pH. Ceux-ci furent toutefois affectés par la hausse de température, qui entraîna une diminution du ratio N:P de consommation des nutriments, accéléra le développement de la floraison phytoplanctonique et l’épuisement des nutriments, puis mena à un changement taxonomique en fin d’expérience. Ce changement est possiblement responsable des différences observées dans la composition de la matière organique particulaire (POM) lors du déclin de la floraison planctonique (diminution des ratios POC:PON, POC:POP,POC:BSi et hausse du ratio BSi:PON). Ces résultats suggèrent que pour l’estuaire maritime du Saint-Laurent, le réchauffement pourrait entraîner des changements stœchiométriques au sein de la POM avec des conséquences probables pour les niveaux trophiques supérieurs et la pompe biologique.

Continue reading ‘Étude en mésocosmes des impacts de l’acidification et du réchauffement sur la composition élémentaire de la biomasse planctonique et le cycle de l’azote dans l’estuaire maritime du Saint-Laurent (in French)’

Trans‐life cycle acclimation to experimental ocean acidification affects gastric pH homeostasis and larval recruitment in the sea star Asterias rubens

Aim
Experimental simulation of near‐future ocean acidification (OA) has been demonstrated to affect growth and development of echinoderm larval stages through energy allocation towards ion and pH compensatory processes. To date, it remains largely unknown how major pH regulatory systems and their energetics are affected by trans‐generational exposure to near‐future acidification levels.

Methods
Here we used the common sea star Asterias rubens in a reciprocal transplant experiment comprising different combinations of OA scenarios, in order to study trans‐generational plasticity using morphological and physiological endpoints.

Results
Acclimation of adults to pHT 7.2 (pCO2 3500μatm) led to reductions in feeding rates, gonad weight, and fecundity. No effects were evident at moderate acidification levels (pHT 7.4; pCO2 2000μatm). Parental pre‐acclimation to pHT 7.2 for 85 days reduced developmental rates even when larvae were raised under moderate and high pH conditions, whereas pre‐acclimation to pHT 7.4 did not alter offspring performance. Microelectrode measurements and pharmacological inhibitor studies carried out on larval stages demonstrated that maintenance of alkaline gastric pH represents a substantial energy sink under acidified conditions that may contribute up to 30% to the total energy budget.

Conclusion
Parental pre‐acclimation to acidification levels that are beyond the pH that is encountered by this population in its natural habitat (e.g. pHT 7.2) negatively affected larval size and development, potentially through reduced energy transfer. Maintenance of alkaline gastric pH and reductions in maternal energy reserves probably constitute the main factors for a reduced juvenile recruitment of this marine keystone species under simulated OA.

Continue reading ‘Trans‐life cycle acclimation to experimental ocean acidification affects gastric pH homeostasis and larval recruitment in the sea star Asterias rubens’

Ocean acidification changes the structure of an Antarctic coastal protistan community (update)

Antarctic near-shore waters are amongst the most sensitive in the world to ocean acidification. Microbes occupying these waters are critical drivers of ecosystem productivity, elemental cycling and ocean biogeochemistry, yet little is known about their sensitivity to ocean acidification. A six-level, dose–response experiment was conducted using 650 L incubation tanks (minicosms) adjusted to a gradient in fugacity of carbon dioxide (fCO2) from 343 to 1641 µatm. The six minicosms were filled with near-shore water from Prydz Bay, East Antarctica, and the protistan composition and abundance was determined by microscopy during 18 days of incubation. No CO2-related change in the protistan community composition was observed during the initial 8 day acclimation period under low light. Thereafter, the response of both autotrophic and heterotrophic protists to fCO2 was species-specific. The response of diatoms was mainly cell size related; microplanktonic diatoms ( >  20 µm) increased in abundance with low to moderate fCO2 (343–634 µatm) but decreased at fCO2  ≥  953 µatm. Similarly, the abundance of Phaeocystis antarctica increased with increasing fCO2 peaking at 634 µatm. Above this threshold the abundance of micro-sized diatoms and P. antarctica fell dramatically, and nanoplanktonic diatoms ( ≤  20 µm) dominated, therefore culminating in a significant change in the protistan community composition. Comparisons of these results with previous experiments conducted at this site show that the fCO2 thresholds are similar, despite seasonal and interannual differences in the physical and biotic environment. This suggests that near-shore microbial communities are likely to change significantly near the end of this century if anthropogenic CO2 release continues unabated, with profound ramifications for near-shore Antarctic ecosystem food webs and biogeochemical cycling.

Continue reading ‘Ocean acidification changes the structure of an Antarctic coastal protistan community (update)’

Transgenerational deleterious effects of ocean acidification on the reproductive success of a keystone crustacean (Gammarus locusta)

Highlights

• High CO2 reduced survival and mate-guarding duration.
• Initial stimulation of egg production in F0 was followed by a decline in F1.
• Drop in fecundity revealed in the second generation under high CO2.
• Overall negative carry-over effects of transgenerational exposure to high CO2.

Abstract

Ocean acidification (OA) poses a global threat to marine biodiversity. Notwithstanding, marine organisms may maintain their performance under future OA conditions, either through acclimation or evolutionary adaptation. Surprisingly, the transgenerational effects of high CO2 exposure in crustaceans are still poorly understood. For the first time, the present study investigated the transgenerational effect of OA, from hatching to maturity, of a key amphipod species (Gammarus locusta). Negative transgenerational effects were observed on survival of the acidified lineage, resulting in significant declines (10–15%) compared to the control groups in each generation. Mate-guarding duration was also significantly reduced under high CO2 and this effect was not alleviated by transgenerational acclimation, indicating that precopulatory behaviours can be disturbed under a future high CO2 scenario. Although OA may initially stimulate female investment, transgenerational exposure led to a general decline in egg number and fecundity. Overall, the present findings suggest a potential fitness reduction of natural populations of G. locusta in a future high CO2 ocean, emphasizing the need of management tools towards species’ sustainability.

Continue reading ‘Transgenerational deleterious effects of ocean acidification on the reproductive success of a keystone crustacean (Gammarus locusta)’

Sex differences in oxidative stress responses of tropical topshells (Trochus histrio) to increased temperature and high pCO2

Highlights

• Sex differences in oxidative stress of topshells were investigated under climate change.
• Males undergo cellular damage under high pCO2, counter-balanced by increased temperature.
• Heat shock response was thermo- and sex-regulated, most predominant in males.
• Catalase and GSTs activities were maximum under high temperature and hypercapnia.
• Sexes have distinct physiological strategies to cope oxidative stress, more efficient in females.

Abstract

Given scarcity of knowledge on gender ecophysiological responses of tropical marine organisms to global climate change, the major aim of this research was to investigate potential sex differences in oxidative status of topshell Trochus histrio, after a combined exposure to increased temperature and pCO2. Lipid peroxidation, heat-shock response and antioxidant enzymatic activities were evaluated. Lipid peroxidation varied differently between sexes, with males undergoing cellular damage under high pCO2, which was elevated temperature-counteracted. Heat shock response was thermo- and sex-regulated, with males exhibiting significantly higher heat shock proteins production than females. Catalase activity increased with temperature and was exacerbated in combination with hypercapnia, being highest in females, while glutathione S-transferases activity peaked in males. These results clearly support the existence of distinct physiological strategies to cope oxidative stress between sexes, apparently more efficient in females, and also reinforce for the need of encompassing sex as meaningful variable in future biomarker studies.

Continue reading ‘Sex differences in oxidative stress responses of tropical topshells (Trochus histrio) to increased temperature and high pCO2’

Behavioural responses of Antarctic krill (Euphausia superba) to CO2-induced ocean acidification: would krill really notice?

The Southern Ocean is expected to be significantly affected by future ocean acidification. Antarctic krill (Euphausia superba) is the key species of the Southern Ocean ecosystem. Understanding their behavioural responses to acidification is critical for assessing the impacts of ocean acidification on the ecosystem. Adult Antarctic krill reared in different holding tanks with various CO2 levels for 6 months prior to the experiments were tested for their behavioural responses to different carbon dioxide partial pressures (pCO2) (400, 1000, 1500, 2000, and 4000 μatm pCO2) in a two-channel flume. The time krill occupied either of the flume channels (with high or ambient CO2 levels) was highly variable in all tests. In most cases no significant preference to either side of the flume was found. The krill did not display any systematic discrimination to the sea water with different CO2 levels regardless of the CO2 levels that krill were acclimated for in the 6 months prior to the experiment. Poor ability to discriminate high CO2 waters may have an important implication to their life history in the future as ocean acidification rapidly progresses in parts of Southern Ocean.

Continue reading ‘Behavioural responses of Antarctic krill (Euphausia superba) to CO2-induced ocean acidification: would krill really notice?’


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OA-ICC HIGHLIGHTS

Ocean acidification in the IPCC AR5 WG II

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