摘要
We studied the effects of expected end-of-the-century p CO_2(1000 ppm)on the photosynthetic performance of a coastal marine cyanobacterium Synechococcus sp.PCC7002 during the lag,exponential,and stationary growth phases.Elevated p CO_2significantly stimulated growth,and enhanced the maximum cell density during the stationary phase.Under ambient p CO_2conditions,the lag phase lasted for 6 days,while elevated p CO_2shortened the lag phase to two days and extended the exponential phase by four days.The elevated p CO_2increased photosynthesis levels during the lag and exponential phases,but reduced them during the stationary phase.Moreover,the elevated p CO_2reduced the saturated growth light(Ik)and increased the light utilization efficiency(α)during the exponential and stationary phases,and elevated the phycobilisome:chlorophyll a(Chl a)ratio.Furthermore,the elevated p CO_2reduced the particulate organic carbon(POC):Chl a and particulate organic nitrogen(PON):Chl a ratios during the lag and stationary phases,but enhanced them during the exponential phase.Overall,Synechococcus showed differential physiological responses to elevated p CO_2during different growth phases,thus providing insight into previous studies that focused on only the exponential phase,which may have biased the results relative to the effects of elevated p CO_2in ecology or aquaculture.
We studied the effects of expected end-of-the-century p CO2（1000 ppm）on the photosynthetic performance of a coastal marine cyanobacterium Synechococcus sp.PCC7002 during the lag,exponential,and stationary growth phases.Elevated p CO2significantly stimulated growth,and enhanced the maximum cell density during the stationary phase.Under ambient p CO2conditions,the lag phase lasted for 6 days,while elevated p CO2shortened the lag phase to two days and extended the exponential phase by four days.The elevated p CO2increased photosynthesis levels during the lag and exponential phases,but reduced them during the stationary phase.Moreover,the elevated p CO2reduced the saturated growth light（Ik）and increased the light utilization efficiency（α）during the exponential and stationary phases,and elevated the phycobilisome：chlorophyll a（Chl a）ratio.Furthermore,the elevated p CO2reduced the particulate organic carbon（POC）：Chl a and particulate organic nitrogen（PON）：Chl a ratios during the lag and stationary phases,but enhanced them during the exponential phase.Overall,Synechococcus showed differential physiological responses to elevated p CO2during different growth phases,thus providing insight into previous studies that focused on only the exponential phase,which may have biased the results relative to the effects of elevated p CO2in ecology or aquaculture.
基金
supported by the National Key Research and Development Program of China (Grant No. 2016YFA0601402)
the China SOA Grant Associated with Task (Grant No. GASI-03-01-02-05)
the CNOOC Zhanjiang Branch (Grant No. CNOOC-KJ 125 FZDXM 00 ZJ 001-2014)
the National Natural Science Foundation of China (Grant Nos. 41606092 & 41676156)
