Zheng Ying, Giordano Mario, Gao Kunshan
State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen 361005, China.
Dipartimento di Scienze della Vita e dell'Ambiente, Università Politecnica delle Marche, Via Brecce Bianche, 60131 Ancona, Italy; Institute of Microbiology ASCR, Algatech, Trebon 37981, Czech Republic.
J Plant Physiol. 2015 May 15;180:18-26. doi: 10.1016/j.jplph.2015.01.020. Epub 2015 Mar 24.
Increasing atmospheric pCO2 and its dissolution into oceans leads to ocean acidification and warming, which reduces the thickness of upper mixing layer (UML) and upward nutrient supply from deeper layers. These events may alter the nutritional conditions and the light regime to which primary producers are exposed in the UML. In order to better understand the physiology behind the responses to the concomitant climate changes factors, we examined the impact of light fluctuation on the dinoflagellate Prorocentrum micans grown at low (1 μmol L(-1)) or high (800 μmol L(-1)) [NO3(-)] and at high (1000 μatm) or low (390 μatm, ambient) pCO2. The light regimes to which the algal cells were subjected were (1) constant light at a photon flux density (PFD) of either 100 (C100) or 500 (C500) μmol m(-2) s(-1) or (2) fluctuating light between 100 or 500 μmol photons m(-2) s(-1) with a frequency of either 15 (F15) or 60 (F60) min. Under continuous light, the initial portion of the light phase required the concomitant presence of high CO2 and NO3(-) concentrations for maximum growth. After exposure to light for 3h, high CO2 exerted a negative effect on growth and effective quantum yield of photosystem II (F'(v)/F'(m)). Fluctuating light ameliorated growth in the first period of illumination. In the second 3h of treatment, higher frequency (F15) of fluctuations afforded high growth rates, whereas the F60 treatment had detrimental consequences, especially when NO3(-) concentration was lower. F'(v)/F'(m) respondent differently from growth to fluctuating light: the fluorescence yield was always lower than at continuous light at 100 μmol m(-2) s(-1), and always higher at 500 μmol m(-2) s(-1). Our data show that the impact of atmospheric pCO2 increase on primary production of dinoflagellate depends on the availability of nitrate and the irradiance (intensity and the frequency of irradiance fluctuations) to which the cells are exposed. The impact of global change on oceanic primary producers would therefore be different in waters with different chemical and physical (mixing) properties.
大气中pCO₂的增加及其向海洋中的溶解导致海洋酸化和变暖，这会减小上层混合层（UML）的厚度以及深层向上的养分供应。这些变化可能会改变初级生产者在UML中所面临的营养条件和光照环境。为了更好地理解对伴随气候变化因素的响应背后的生理机制，我们研究了光照波动对在低（1 μmol L⁻¹）或高（800 μmol L⁻¹）[NO₃⁻]以及高（1000 μatm）或低（390 μatm，环境水平）pCO₂条件下生长的海洋甲藻微小原甲藻的影响。藻类细胞所经历的光照条件为：（1）光子通量密度（PFD）为100（C100）或500（C500）μmol m⁻² s⁻¹的恒定光照，或（2）在100或500 μmol光子 m⁻² s⁻¹之间以15（F15）或60（F60）分钟的频率波动的光照。在连续光照下，光阶段的初始部分需要同时存在高浓度的CO₂和NO₃⁻才能实现最大生长。在光照3小时后，高CO₂浓度对生长和光系统II的有效量子产率（F'(v)/F'(m)）产生负面影响。波动光照在光照的第一阶段改善了生长情况。在处理的第二个3小时内，较高频率（F15）的波动带来了较高的生长速率，而F60处理则产生了不利影响，尤其是在NO₃⁻浓度较低时。F'(v)/F'(m)对波动光照的响应与生长情况不同：荧光产率在100 μmol m⁻² s⁻¹的连续光照下始终较低，而在500 μmol m⁻² s⁻¹时始终较高。我们的数据表明，大气pCO₂增加对海洋甲藻初级生产的影响取决于硝酸盐的可利用性以及细胞所暴露的辐照度（强度和辐照度波动频率）。因此，全球变化对海洋初级生产者的影响在具有不同化学和物理（混合）特性的水域中会有所不同。
