海水升温与氮限制对三角褐指藻生长及光合作用的影响

Effects of ocean warming and nitrogen limitation on growth and photosynthesis of Phaeodactylum tricornutum

以硅藻三角褐指藻为实验材料,研究升温(24℃)与氮限制(40μmol/L)对藻细胞生长及光合特性的影响。结果显示,氮限制使得电子从Q_A^-到Q_B的传递受阻,降低了其对光能的吸收利用效率,导致其对高光强的耐受能力下降,从而降低生长速率。而升温并未影响三角褐指藻细胞电子传递速率、单位反应中心耗散的能量(DI_o/RC)、捕获的用于还原Q_A的能量(TR_o/RC)以及吸收的能量(ABS/RC)等,表明升温对其PSⅡ光化学反应影响不显著。但应对高光强时,升温使得藻细胞修复速率降低,导致藻细胞受光抑制明显。本研究表明,相对于温度,氮限制对三角褐指藻细胞光合作用和生长的影响更为显著,而海水升温与氮限制耦合作用会进一步影响三角褐指藻的初级生产贡献。

The marine diatom Phaeodactylum tricornutum was selected as experimental material to investigate the impact of ocean warming (24 ℃) and nitrogen limitation (40 μmol/L) on its growth and photosynthetic characteristics. Results showed that nitrogen limitation inhibited the electron transfer from QA- to QB, reduced the absorption and utilization of light energy, lowered the resistant capacity of P. tricornutum to high light intensity, thus resulting in the reduction of growth rate. In contrast, temperature rise did not bring about significant changes on the electron transfer rate, the energy fluxes for dissipation (DIo /RC), trapping (TRo/RC), and absorption (ABS/RC) per reaction center. It appeared that the PSII photochemistry was not significantly affected by ocean warming. However, when cells were exposed to high light challenge, the repair rate was decreased by the rise of temperature, leading to marked photoinhibition. Our study indicated that the photosynthesis and growth of P. tricornutum were affected to a greater extent by nitrogen limitation than the rise of temperature, whereas the combination of temperature rise and nitrogen limitation further affected the primary production contribution of P. tricornutum.