Water warming, either resulting from global or local drivers, is of growing concern for aquatic environments. Changes in thermal regimes may alter the functioning and the trophic dynamics of river ecosystems as most aquatic biota like micro-algae, invertebrates, or fish are poikilotherms. Because biofilms integrate basal and intermediate components of aquatic food webs, examination of their responses to warming should contribute to a better understanding of the effects of ongoing climate change on river ecosystems. In this study, we considered sites that were or were not exposed directly to thermal effluents from a nuclear power plant as “in situ laboratories” of the effect of climate change and water warming. To compare the structure of algal and invertebrate communities dwelling in epilithic biofilms subjected to different thermal regimes in the Garonne River, sets of concrete tiles were placed in the river and the biofilm growing on these standard substrates was sampled after two months of colonisation. The site located within the thermal plume directly downstream of the thermal effluents showed warmer average water temperature (mean ΔT of about 1.5 °C over the study period) and greater daily temperature fluctuations in comparison to the control site. Algal and invertebrate biomass did not differ significantly, but the structure of communities differed markedly between sites. At the heated site, the proportion of cyanobacteria was higher, while there were fewer micro-crustaceans and larvae of insects and bivalves. However, the population of chironomids showed a greater proportion of relatively large individuals. Interestingly, nematodes were more abundant, and their communities comprised more species at the heated site. Their feeding-types were also more diverse showing a greater proportion of algivores, large-sized omnivorous and predatory species. Changes in the abundance and age structure further showed that some bacterivore species, such as Eumonhystera vulgaris, thrived especially well at the heated site, whereas another bacterivore, Monhystrella paramacrura, thrived well at the control site. In the context of climate change, our results highlight that warmer and more fluctuating water temperatures have the potential to alter the body-size spectrum, species composition, distribution of feeding specialisations and age structure within biofilm-dwelling communities.

无论是全球还是当地的驱动因素导致的水变暖，对水生环境越来越引起关注。由于大多数水生生物，如微藻，无脊椎动物或鱼类，都是高温热疗，因此热态的变化可能会改变河流生态系统的功能和营养动力学。由于生物膜整合了水生食物网的基础和中间组成部分，因此检查其对变暖的反应应有助于更好地了解持续的气候变化对河流生态系统的影响。在这项研究中，我们将直接暴露于或未暴露于核电站热废水的场所视为“原位” 。实验室”来研究气候变化和水变暖的影响。为了比较居住在加龙河中受不同热力作用的上石器时代生物膜中藻类和无脊椎动物群落的结构，在河中放置了几组混凝土砖，并在定居两个月后对生长在这些标准基质上的生物膜进行了采样。与控制站点相比，位于热流出物正下游的热羽流中的站点显示出较高的平均水温（研究期间的平均ΔT约为1.5°C），并且每日温度波动更大。藻类和无脊椎动物的生物量没有显着差异，但站点之间的群落结构显着不同。在加热的地方，蓝细菌的比例更高，而昆虫和双壳类的微甲壳类和幼虫较少。然而，手足动物的种群显示出较大比例的较大个体。有趣的是，线虫更加丰富，并且它们的群落在受热地点包括更多的物种。它们的摄食类型也更加多样化，显示出更大比例的食虫动物，大型杂食性和掠食性物种。丰度和年龄结构的变化进一步表明某些噬菌体物种，例如 大型杂食性和掠食性物种。丰度和年龄结构的变化进一步表明某些噬菌体物种，例如 大型杂食性和掠食性物种。丰度和年龄结构的变化进一步表明某些噬菌体物种，例如Eumonhystera vulgaris，在受热部位尤其旺盛，而另一种噬菌体Parahyprella Monhystrella paramacrura在对照处旺盛。在气候变化的背景下，我们的研究结果表明，水温升高和波动更大，有可能改变生物膜居住社区的体形谱，物种组成，喂养专长分布和年龄结构。