State Key Laboratory of Marine Environmental Science & College of Ocean and Earth Sciences, Xiamen University, Xiamen, 361005, China; College of Life and Environmental Sciences, Huangshan University, Huangshan, 245041, China.
State Key Laboratory of Marine Environmental Science & College of Ocean and Earth Sciences, Xiamen University, Xiamen, 361005, China.
Mar Environ Res. 2020 Sep;160:104965. doi: 10.1016/j.marenvres.2020.104965. Epub 2020 Mar 28.
Phytoplankton in the upper oceans are exposed to changing light levels due to mixing, diurnal solar cycles and weather conditions. Consequently, effects of ocean acidification are superimposed upon responses to variable light levels. We therefore grew a model diatom Thalassiosira pseudonana under either constant or variable light but at the same daily photon dose, with current low (400 μatm, LC) and future high CO (1000 μatm, HC) treatments. Variable light, compared with the constant light regime, decreased the growth rate, Chl a, Chl c, and carotenoid contents under both LC and HC conditions. Cells grown under variable light appeared more tolerant of high light as indicated by higher maximum relative electron transport rate and saturation light. Light variation interacted with high CO/lowered pH to decrease the carbon fixation rate, but increased particulate organic carbon (POC) and particularly nitrogen (PON) per cell, which drove a decrease in C/N ratio, reflecting changes in the efficiency of energy transfer from photo-chemistry to net biomass production. Our results imply that elevated pCO under varying light conditions can lead to less primary productivity but more PON per biomass of the diatom, which might improve the food quality of diatoms and thereby influence biogeochemical nitrogen cycles.
上层海洋中的浮游植物由于混合、日太阳周期和天气条件的变化而暴露在不断变化的光照水平下。因此，海洋酸化的影响叠加在对可变光照水平的反应上。因此，我们在相同的每日光子剂量下，在恒光或变光但在相同的每日光子剂量下，分别在当前低（400 μatm，LC）和未来高 CO（1000 μatm，HC）条件下培养了一种模式硅藻假鱼腥藻。与恒光相比，在 LC 和 HC 条件下，变光都会降低生长速率、叶绿素 a、叶绿素 c 和类胡萝卜素含量。在变光下生长的细胞似乎对高光更具耐受性，表现为更高的最大相对电子传递率和饱和光。光照变化与高 CO/降低 pH 相互作用会降低碳固定率，但会增加每个细胞的颗粒有机碳 (POC) 和特别是氮 (PON)，这会降低 C/N 比，反映出从光化学到净生物量生产的能量转移效率的变化。我们的结果表明，在不断变化的光照条件下，升高的 pCO2 可能导致初级生产力降低，但每个硅藻生物量的 PON 增加，这可能提高硅藻的食物质量，从而影响生物地球化学氮循环。
