Centre d'Estudis Avançats de Blanes. CEAB-CSIC, C/Acceso a la Cala St. Francesc 14, 17300 Blanes, Girona, Spain.
Environ Monit Assess. 2012 Jun;184(6):3675-86. doi: 10.1007/s10661-011-2215-3. Epub 2011 Jul 22.
The European Water Framework Directive commits partner countries to evolve uniform protocols for monitoring the environmental condition of natural water bodies, crucially integrating biological and ecological criteria from the associated ecosystems. This has encouraged considerable research on the development of bioindicator-based systems of water quality monitoring. A critical step towards this end is providing evidence that the proposed bioindicator system adequately reflects the human pressures to which a specific water body is submitted. Here we investigate the utility of pulse-amplitude-modulated (PAM) fluorometry, a fast, non-destructive and increasingly popular bioindicator-based method, in assessing water quality based on the widespread Mediterranean seagrass Posidonia oceanica, an important constituent of submersed benthic vegetation. Specifically, we evaluated the ability of PAM to discriminate between sites along a pre-established gradient of anthropogenic pressures and the consistency and reliability of PAM parameters across spatial scales. Our results show that the maximum quantum yield (Fv/Fm), representing the structural photosynthetic efficiency of the plant, responds significantly to the degree of site-level anthropogenic pressure. However, Fv/Fm values in our study increased with increasing pressure, in striking contrast with other studies that report declines in Fv/Fm values with increasing stress. A potential explanation for this discrepancy is that our study sites were influenced by multiple diffuse stressors (characteristic of most coastal waters) that could potentially interact with each other to influence Fv/Fm values in often unpredictable ways. The photosynthetic variables calculated from rapid light curves (ETR(max), maximum electron transport rate; α, initial slope of the curve; I (k), saturating irradiance), which represent an instant picture of the photosynthetic activity of the plant, were unable to clearly discriminate between sites subject to different anthropogenic pressures due to considerable small-scale variability. Taken together, these results suggest that even though PAM fluorometry may be a good candidate tool for monitoring water bodies in terms of costs and applicability, considerably more needs to be understood about how its parameters respond to real-world stressors, particularly when they act in concert with each other. With our present understanding of seagrass photosynthetic responses to anthropogenic stress, it would be ill advised to employ PAM as anything but a complementary tool to validate environmental stress derived with other, more robust methodologies.
《欧洲水框架指令》促使合作国家制定统一的监测自然水体环境状况的协议，关键是要将相关生态系统的生物和生态标准纳入其中。这鼓励了大量关于开发基于生物指标的水质监测系统的研究。为此，至关重要的一步是提供证据，证明所提议的生物指标系统充分反映了特定水体所承受的人为压力。在这里，我们研究了脉冲幅度调制（PAM）荧光计的实用性，这是一种快速、非破坏性且越来越受欢迎的基于生物指标的方法，用于评估广泛分布的地中海海草波西多尼亚海洋床的水质，这是底栖植物的重要组成部分。具体而言，我们评估了 PAM 在评估沿预先确定的人为压力梯度的地点方面的能力，以及 PAM 参数在空间尺度上的一致性和可靠性。我们的结果表明，最大量子产量（Fv/Fm）代表植物的结构光合作用效率，对地点级别的人为压力程度有显著响应。然而，我们研究中的 Fv/Fm 值随着压力的增加而增加，这与其他报告随着压力增加 Fv/Fm 值下降的研究形成鲜明对比。对于这种差异的一个潜在解释是，我们的研究地点受到多种扩散压力源的影响（这是大多数沿海水域的特征），这些压力源可能相互作用，以难以预测的方式影响 Fv/Fm 值。从快速光曲线计算的光合作用变量（最大电子传递速率 ETR(max)；α，曲线的初始斜率；I(k)，饱和辐照度），代表植物光合作用的即时图片，由于小尺度变异性很大，无法清楚地区分受到不同人为压力的地点。总的来说，这些结果表明，尽管 PAM 荧光计可能是一种具有成本效益和适用性的监测水体的良好候选工具，但需要更多地了解其参数如何响应实际压力源，特别是当它们相互协同作用时。考虑到海草对人为压力的光合反应的现有理解，除了作为验证其他更强大方法得出的环境压力的补充工具外，不建议将 PAM 用作其他用途。
