Alleviation of solar ultraviolet radiation (UVR)-induced photoinhibition in diatom Chaetoceros curvisetus by ocean acidification

The study aimed to unravel the interaction between ocean acidification and solar ultraviolet radiation (UVR) in Chaetoceros curvisetus. Chaetoceros curvisetus cells were acclimated to high CO2 (HC, 1000 ppmv) and low CO2 concentration (control, LC, 380 ppmv) for 14 days. Cell density, specific growth rate and chlorophyll were measured. The acclimated cells were then exposed to PAB (photosynthetically active radiation (PAR) + UV-A + UV-B), PA (PAR + UV-A) or P (PAR) for 60 min. Photochemical efficiency (phi PSII), relative electron transport rate (rETR) and the recovery of PHPSII were determined. HC induced higher cell density and specific growth rate compared with LC. However, no difference was found in chlorophyll between HC and LC. Moreover, phi PSII and rETRs were higher under HC than LC in response to solar UVR. P exposure led to faster recovery of phi PSII, both under HC and LC, than PA and PAB exposure. It appeared that harmful effects of UVR on C. curvisetus could be counteracted by ocean acidification simulated by high CO2 when the effect of climate change is not beyond the tolerance of cells.

本研究旨在揭示海洋酸化与太阳紫外线辐射（UVR）对弯角毛藻（Chaetoceros curvisetus）的相互作用。弯角毛藻细胞在高CO₂（HC，1000 ppmv）和低CO₂浓度（对照组，LC，380 ppmv）条件下驯化14天，期间测定细胞密度、比生长速率及叶绿素含量。驯化后的细胞随后暴露于PAB（光合有效辐射（PAR）+紫外线A+紫外线B）、PA（PAR+紫外线A）或P（PAR）条件下60分钟，测定光化学效率（phi PSII）、相对电子传递速率（rETR）及PHPSII的恢复情况。与LC组相比，HC组诱导了更高的细胞密度和比生长速率；然而，两组之间的叶绿素含量无显著差异。此外，在太阳UVR照射下，HC组的phi PSII和rETRs值高于LC组。无论是HC组还是LC组，暴露于P条件下的phi PSII恢复速度均快于暴露于PA和PAB条件下的恢复速度。研究表明，当气候变化的影响未超出细胞耐受范围时，高CO₂模拟的海洋酸化可抵消UVR对弯角毛藻（C. curvisetus）的有害影响。