We studied the effects of expected end-of-the-century
pCO
2 (1000 ppm) on the photosynthetic performance of a coastal marine cyanobacterium
Synechococcus sp. PCC7002 during the lag, exponential, and stationary growth phases. Elevated
pCO
2 significantly stimulated growth, and enhanced the maximum cell density during the stationary phase. Under ambient
pCO
2 conditions, the lag phase lasted for 6 days, while elevated
pCO
2 shortened the lag phase to two days and extended the exponential phase by four days. The elevated
pCO
2 increased photosynthesis levels during the lag and exponential phases, but reduced them during the stationary phase. Moreover, the elevated
pCO
2 reduced 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
pCO
2 reduced 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
pCO
2 during 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
pCO
2 in ecology or aquaculture.
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