Effect of dead phytoplankton cells on the apparent efficiency of photosystem II
Effect of dead phytoplankton cells on the apparent efficiency of photosystem II
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DOI：
10.3354/meps07967
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发表时间：
2009-01-01
影响因子：
2.5
通讯作者：
Berges, John A.
中科院分区：
文献类型：
--
作者：
Franklin, Daniel J.;Choi, Chang Jae;Berges, John A.
光系统（PS）II的效率的测量已成为生物海洋学中广泛使用的，各种形式被用来评估海洋浮游植物的“健康”，并帮助估计初级生产力。PS II效率的绝对值在一定程度上取决于测量系统，但PS II效率的变化最常见的解释是细胞适应不断变化的辐照度（包括光适应和光抑制）和营养物质的可用性（特别是N和Fe）。最近对海洋表层浮游植物生存能力的测量表明，在许多区域，浮游植物群落可能含有大比例的死细胞。这些死细胞对表观PS II效率的影响在很大程度上是未知的。通过混合活细胞和死细胞并测量PS II效率，我们发现光合作用无功能（死）细胞的存在对PS II的影响令人惊讶地小。在一些物种中，50%的细胞死亡的混合物的值为0.5，与通常在自然组合中发现的值相似。一个简单的模型表明，荧光比的非线性性质是造成这一意外结果的原因。我们得出结论，PS II效率相对较高的值不能作为低死亡率的证据。我们的研究结果强调了需要更多的真核和原核微藻在自然界中的生理状态的信息。
Measurements of the efficiency of photosystem (PS) II have become widespread in biological oceanography, and various forms are used to assess the 'health' of marine phytoplankton and to help estimate primary productivity. Absolute values of PS II efficiency depend to some extent on the measuring system, but changes in PS II efficiency are most commonly interpreted in terms of cellular acclimations to changing irradiance (including photoacclimation and photoinhibition) and nutrient availability (especially N and Fe). Recent measurements of phytoplankton viability in the surface ocean have revealed that in many regions phytoplankton assemblages may contain large proportions of dead cells. The effect of these dead cells on apparent PS II efficiency is largely unknown. By mixing live and dead cells and measuring PS II efficiency, we show that the presence of photosynthetically non-functional (dead) cells has surprisingly little effect.; in a number of species, mixtures ill which 50%, of the cells were dead had values of 0.5, similar to values often found in natural assemblages. A simple model indicates that the non-linear nature of the fluorescence ratio is responsible for this unexpected result. We conclude that relatively high values of PS II efficiency cannot be used as evidence of low mortality. Our findings highlight the need for more information on the physiological status of both eukaryotic and prokaryotic microalgae in nature.