River biofilms are a suitable indicator of toxic stress in aquatic ecosystems commonly exposed to various anthropogenic pollutants from industrial, domestic, and agricultural sources. Among these pollutants, heavy metals are of particular concern as they are known to interfere with various physiological processes of river biofilm, directly or indirectly related to photosynthetic performance. Nevertheless, only limited toxicological data are available on the mechanisms and toxicodynamics of heavy metals in biofilms. Pulse Amplitude Modulated (PAM) fluorometry is a rapid, non-disruptive, well-established technique to monitor toxic responses on photosynthetic performance, fluorescence-kinetics, and changes in yield in other non-photochemical processes. In this study, a new micro-PAM-sensor was tested to assess potential acute and chronic effects of heavy metals in river biofilm. Toxicity values across the three parameters considered in this study (photosynthetic yield YII, non-photochemical quenching NPQ, and basal fluorescence F₀) were comparable, as determined EC50 were within one order of magnitude (EC50 ∼1−10 mg L⁻¹). However, the stimulation of NPQ was more clearly associated with early acute effects, especially in illuminated samples, while depression of YII and F₀ were more prevalent in chronic tests. These results have implications for the development of functional indicators for the biomonitoring of aquatic health, in particular for the use of river biofilm as a bioindicator of water quality. In conclusion, the approach proposed seems promising to characterize and monitor the exposure and impact of heavy metals on river periphyton communities. Furthermore, this study provides a fast, highly sensitive, inexpensive, and accurate laboratory method to test effects of pollutants on complex periphyton communities that can also give insights regarding the probable toxicological mechanisms of heavy metals on photosynthetic performance in the river biofilm.

河流生物膜是通常暴露于工业，家庭和农业来源的各种人为污染物的水生生态系统中毒性胁迫的合适指示。在这些污染物中，重金属尤其受到关注，因为已知重金属会干扰河流生物膜的各种生理过程，这些过程直接或间接与光合作用有关。然而，关于生物膜中重金属的机理和毒理动力学的毒理学数据有限。脉冲幅度调制（PAM）荧光测定法是一种快速，无中断的，完善的技术，用于监视对光合作用，荧光动力学和其他非光化学过程中产率变化的毒性反应。在这个研究中，测试了一种新型微型PAM传感器，以评估河流生物膜中重金属的潜在急性和慢性影响。这项研究中考虑的三个参数（光合产率YII，非光化学猝灭NPQ和基础荧光F₀）是可比较的，因为确定的EC50在一个数量级内（EC50〜1-10 mg L ^-1）。但是，NPQ的刺激与早期急性效应更明显相关，尤其是在光照样品中，而YII和F _0降低在慢性检查中更为普遍。这些结果对开发用于水生健康生物监测的功能指标具有重要意义，特别是对于利用河流生物膜作为水质生物指标的情况。总之，所提出的方法似乎有望表征和监测重金属对河边植物群落的暴露和影响。此外，这项研究提供了一种快速，高度灵敏，廉价且准确的实验室方法来测试污染物对复杂的附生生物群落的影响，还可以提供有关重金属可能对河流生物膜光合作用性能的毒理学机制的见识。