The palaeo-atmospheric CO_(2)concentration(pCOz)variation in the Yumen,Gansu Province during the middle Cretaceous has been reconstructed using the newly established plant photosynthetic gas exchange mechanistic model...The palaeo-atmospheric CO_(2)concentration(pCOz)variation in the Yumen,Gansu Province during the middle Cretaceous has been reconstructed using the newly established plant photosynthetic gas exchange mechanistic model,and the results show that the pCO_(2)values are in the range of about 550-808 ppmv.The present pCO_(2)values are higher than the pCO_(2)results(531-641 ppmv)of the previous study according to the Recent standardization of the stomatal ratio method,and much lower than the pCO_(2)results(882-1060 ppmv)according to the Carboniferous standardization of the stomatal ratio method.The present pCOz variation is not only within the error range of GEOCARB II and GEOCARB Ill but also is similar to the reconstructed results based on the biochemistry and carbon isotope models.Besides,the present Brachyphyllum specimens were collected from four consecutive horizons of the upper Zhonggou Formation of the Hanxia Section,and the reconstructed pCO_(2)exhibits the reconstructed pCO_(2)exhibits a decline trend during the late Aptian to early Albian.This decline variation is probably associated with the Oceanic Anoxic Events(OAElb)and the Cold snap event.With the combination of pCO_(2)during the Albian to Cenomanian recovered by the plant photosynthetic gas exchange mechanistic model,the pCO_(2)showed a prominent increase during the late Aptian to early Cenominian,which indicates a response to the greenhouse warming during the middle Cretaceous.Therefore,the mechanical model of the plant photosynthetic gas exchange shows a relatively strong accuracy in the reconstruction of thepCO_(2)and can reflect a strong relation between the atmospheric CO_(2)concentrations and climatic events.展开更多
Cyanobacterial blooms,exacerbated by climate change and eutrophication,increasingly compromise water quality by producing taste and odor(T&O)compounds including 2-methylisoborneol(MIB).Cyanobacteria synthesize MIB...Cyanobacterial blooms,exacerbated by climate change and eutrophication,increasingly compromise water quality by producing taste and odor(T&O)compounds including 2-methylisoborneol(MIB).Cyanobacteria synthesize MIB by redirecting carbon metabolism intermediates into the methylerythritol phosphate pathway.This process appears to be influenced by rising atmospheric CO_(2) partial pressure(pCO_(2)).This study examines how elevated pCO_(2) affects MIB production in Synechococcus sp.FACHB-1061 under varying nutrient conditions.The results indicate that elevated pCO_(2) boosts cyanobacterial biomass and total MIB yield,particularly in nutrient-rich environments,by reducing limitations in bioavailable inorganic carbon.In contrast,in nutrient-limited conditions,both total MIB concentration and per-cell production significantly increased with higher pCO_(2).Elevated pCO_(2) altered the activities of nitrate reductase and carbonic anhydrase,reducing impaired nitrogen assimilation and enhanced carbon fixation.The increase and compositional changes in extracellular polymeric substances suggested carbon overflow and a decline in cellular quality under insufficient nutrients.Additionally,markers of oxidative stress,such as increased superoxide dismutase activity and higher malondialdehyde levels,suggested that oxidative stress might stimulate secondary metabolite production.Metabolomic analysis revealed that critical intermediates of the Calvin cycle and glycolysis,such as glyceraldehyde-3-phosphate and acetyl-CoA,were upregulated with elevated pCO_(2) in nutrient-limited status,leading to increase of key precursors for MIB.These results highlight the complex interplay between nutrient and rising pCO_(2) in regulating cyanobacterial MIB biosynthesis.The findings suggest that conventional nutrient control strategies for mitigating cyanobacterial blooms and associated T&O issues may need reassessment under future climate scenarios.展开更多
基金the National Natural Science Foundation of China(No.41402007,41602023,40972025)the State Key Laboratory of Palaeobiology and Stratigraphy,Nanjing Institute of Geology and Palaeontology,CAS(No.153102)
文摘The palaeo-atmospheric CO_(2)concentration(pCOz)variation in the Yumen,Gansu Province during the middle Cretaceous has been reconstructed using the newly established plant photosynthetic gas exchange mechanistic model,and the results show that the pCO_(2)values are in the range of about 550-808 ppmv.The present pCO_(2)values are higher than the pCO_(2)results(531-641 ppmv)of the previous study according to the Recent standardization of the stomatal ratio method,and much lower than the pCO_(2)results(882-1060 ppmv)according to the Carboniferous standardization of the stomatal ratio method.The present pCOz variation is not only within the error range of GEOCARB II and GEOCARB Ill but also is similar to the reconstructed results based on the biochemistry and carbon isotope models.Besides,the present Brachyphyllum specimens were collected from four consecutive horizons of the upper Zhonggou Formation of the Hanxia Section,and the reconstructed pCO_(2)exhibits the reconstructed pCO_(2)exhibits a decline trend during the late Aptian to early Albian.This decline variation is probably associated with the Oceanic Anoxic Events(OAElb)and the Cold snap event.With the combination of pCO_(2)during the Albian to Cenomanian recovered by the plant photosynthetic gas exchange mechanistic model,the pCO_(2)showed a prominent increase during the late Aptian to early Cenominian,which indicates a response to the greenhouse warming during the middle Cretaceous.Therefore,the mechanical model of the plant photosynthetic gas exchange shows a relatively strong accuracy in the reconstruction of thepCO_(2)and can reflect a strong relation between the atmospheric CO_(2)concentrations and climatic events.
基金supported by the National Natural Science Foundation of China(No.41977387)the National Research Foundation,Prime Minister’s Office,Singapore under its Campus for Research Excellence and Technological Enterprise(CREATE)program.
文摘Cyanobacterial blooms,exacerbated by climate change and eutrophication,increasingly compromise water quality by producing taste and odor(T&O)compounds including 2-methylisoborneol(MIB).Cyanobacteria synthesize MIB by redirecting carbon metabolism intermediates into the methylerythritol phosphate pathway.This process appears to be influenced by rising atmospheric CO_(2) partial pressure(pCO_(2)).This study examines how elevated pCO_(2) affects MIB production in Synechococcus sp.FACHB-1061 under varying nutrient conditions.The results indicate that elevated pCO_(2) boosts cyanobacterial biomass and total MIB yield,particularly in nutrient-rich environments,by reducing limitations in bioavailable inorganic carbon.In contrast,in nutrient-limited conditions,both total MIB concentration and per-cell production significantly increased with higher pCO_(2).Elevated pCO_(2) altered the activities of nitrate reductase and carbonic anhydrase,reducing impaired nitrogen assimilation and enhanced carbon fixation.The increase and compositional changes in extracellular polymeric substances suggested carbon overflow and a decline in cellular quality under insufficient nutrients.Additionally,markers of oxidative stress,such as increased superoxide dismutase activity and higher malondialdehyde levels,suggested that oxidative stress might stimulate secondary metabolite production.Metabolomic analysis revealed that critical intermediates of the Calvin cycle and glycolysis,such as glyceraldehyde-3-phosphate and acetyl-CoA,were upregulated with elevated pCO_(2) in nutrient-limited status,leading to increase of key precursors for MIB.These results highlight the complex interplay between nutrient and rising pCO_(2) in regulating cyanobacterial MIB biosynthesis.The findings suggest that conventional nutrient control strategies for mitigating cyanobacterial blooms and associated T&O issues may need reassessment under future climate scenarios.
