Trimborn Scarlett, Thoms Silke, Brenneis Tina, Heiden Jasmin P, Beszteri Sara, Bischof Kai
Department of Biogeosciences, Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, 27515, Germany.
Marine Botany, University of Bremen, Bremen, Germany.
Physiol Plant. 2017 Jun;160(2):155-170. doi: 10.1111/ppl.12539. Epub 2017 Mar 3.
To better understand the impact of ocean acidification (OA) and changes in light availability on Southern Ocean phytoplankton physiology, we investigated the effects of pCO (380 and 800 µatm) in combination with low and high irradiance (20 or 50 and 200 µmol photons m s ) on growth, particulate organic carbon (POC) fixation and photophysiology in the three ecologically relevant species Chaetoceros debilis, Fragilariopsis kerguelensis and Phaeocystis antarctica. Irrespective of the light scenario, neither growth nor POC per cell was stimulated by OA in any of the tested species and the two diatoms even displayed negative responses in growth (e.g. C. debilis) or POC content (e.g. F. kerguelensis) under OA in conjunction with high light. For both diatoms, also maximum quantum yields of photosystem II (F /F ) were decreased under these conditions, indicating lowered photochemical efficiencies. To counteract the negative effects by OA and high light, the two diatoms showed diverging photoacclimation strategies. While cellular chlorophyll a (Chl a) and fucoxanthin contents were enhanced in C. debilis to potentially maximize light absorption, F. kerguelensis exhibited reduced Chl a per cell, increased disconnection of antennae from photosystem II reaction centers and strongly lowered absolute electron transport rates (ETR). The decline in ETRs in F. kerguelensis might be explained in terms of different species-specific strategies for tuning the available flux of adenosine triphosphate and nicotinamide adenine dinucleotide phosphate. Overall, our results revealed that P. antarctica was more tolerant to OA and changes in irradiance than the two diatoms, which may have important implications for biogeochemical cycling.
为了更好地理解海洋酸化（OA）和光照可利用性变化对南大洋浮游植物生理的影响，我们研究了在低光和高光强（20或50以及200 μmol光子·m⁻²·s⁻¹）条件下，pCO₂（380和800 μatm）对三种具有生态相关性的物种柔弱角毛藻、克尔格伦氏海冰藻和南极褐胞藻的生长、颗粒有机碳（POC）固定及光生理的影响。无论光照情况如何，在任何测试物种中，OA均未刺激生长或细胞的POC含量，并且在OA与高光共同作用下，两种硅藻甚至在生长（如柔弱角毛藻）或POC含量（如克尔格伦氏海冰藻）方面表现出负面反应。在这些条件下，对于两种硅藻，光系统II的最大量子产率（Fv/Fm）也降低了，表明光化学效率降低。为了抵消OA和高光的负面影响，两种硅藻表现出不同的光适应策略。柔弱角毛藻中细胞叶绿素a（Chl a）和岩藻黄素含量增加，可能是为了最大化光吸收，而克尔格伦氏海冰藻则表现为细胞Chl a减少、天线与光系统II反应中心的连接断开增加以及绝对电子传递速率（ETR）大幅降低。克尔格伦氏海冰藻ETR的下降可能是由于不同的物种特异性策略来调节三磷酸腺苷和烟酰胺腺嘌呤二核苷酸磷酸的可用通量。总体而言，我们的结果表明，南极褐胞藻比两种硅藻对OA和光照变化更具耐受性，这可能对生物地球化学循环具有重要意义。
