Institute of Aquatic Ecology, Facultat de Ciències, Universitat de Girona, Girona, Spain.
Ecotoxicology. 2012 May;21(4):1208-24. doi: 10.1007/s10646-012-0876-5. Epub 2012 Mar 11.
In multiple stress situations, the co-occurrence of environmental and chemical factors can influence organisms' ability to cope with toxicity. In this context, the influence of light adaptation on the response of freshwater biofilms to sudden light changes or to herbicides exposure was investigated by determining various parameters: diatom community composition, photosynthetic parameters, chlorophyll a content, antioxidant enzyme activities. Biofilms were grown in microcosms under sub-optimal, saturating, and high light intensities and showed already described characteristics of shade/light adaptation (community structure, photosynthetic adaptation, etc.). Light history modulated antioxidant and photosynthetic responses of biofilms to the stress caused by short-term exposure to sudden light changes or to herbicides. First biofilms adapted to sub-optimal light intensity (shade-adapted) were found to be more sensitive to an increase in light intensity than high-light adapted ones to a reduction in light intensity. Second, while light history influenced biofilms' response to glyphosate, it had little influence on biofilms' response to copper and none on its response to oxyfluorfen. Indeed glyphosate exposure led to a stronger decrease in photosynthetic efficiency of shade-adapted biofilms (EC(50) = 11.7 mg L(-1)) than of high-light adapted communities (EC(50) = 35.6 mg L(-1)). Copper exposure led to an activation of ascorbate peroxidase (APX) in biofilms adapted to sub-optimal and saturating light intensity while the protein content decreased in all biofilms exposed to copper. Oxyfluorfen toxicity was independent of light history provoking an increase in APX activity. In conclusion this study showed that both previous exposure to contaminants and physical habitat characteristics might influence community tolerance to disturbances strongly.
在多种胁迫条件下，环境和化学因素的共同作用会影响生物应对毒性的能力。在这种情况下，通过测定各种参数来研究光适应对淡水生物膜对突然光照变化或除草剂暴露的反应的影响：硅藻群落组成、光合作用参数、叶绿素 a 含量、抗氧化酶活性。生物膜在微宇宙中于弱光、饱和光和高光强下生长，并表现出已描述的遮荫/光适应特征（群落结构、光合作用适应等）。光历史调制了生物膜对短期暴露于突然光照变化或除草剂引起的胁迫的抗氧化和光合作用反应。首先，发现适应弱光强度（遮荫适应）的生物膜对光照强度增加的敏感性比适应高光强度的生物膜对光照强度降低的敏感性更高。其次，虽然光历史会影响生物膜对草甘膦的反应，但对生物膜对铜的反应影响很小，对其对氧氟草的反应则没有影响。事实上，草甘膦暴露导致遮荫适应生物膜的光合作用效率下降更强（EC50=11.7mg/L），而不是高光适应群落（EC50=35.6mg/L）。铜暴露导致适应弱光和饱和光强度的生物膜中抗坏血酸过氧化物酶（APX）的激活，而所有暴露于铜的生物膜中的蛋白质含量都下降。氧氟草的毒性与光历史无关，会引起 APX 活性增加。总之，这项研究表明，先前暴露于污染物和物理栖息地特征都可能强烈影响群落对干扰的耐受性。
