Impact of urban pollution on freshwater biofilms: Oxidative stress, photosynthesis and lipid responses
Caroline Roux, Cassandre Madru, D. Navarro, Gwilherm Jan, Nicolás Mazzella, Aurélie Moreira, Jacky Vedrenne, Laure Carassou, Soizic Morin
Abstract
Urban ecosystems are subjected to multiple anthropogenic stresses, which impact aquatic communities. Artificial light at night (ALAN) for instance can significantly alter the composition of algal communities as well as the photosynthetic cycles of autotrophic organisms, possibly leading to cellular oxidative stress. The combined effects of ALAN and chemical contamination could increase oxidative impacts in aquatic primary producers, although such combined effects remain insufficiently explored. To address this knowledge gap, a one-month experimental approach was implemented under controlled conditions to elucidate effects of ALAN and dodecylbenzyldimethylammonium chloride (DDBAC) on aquatic biofilms. DDBAC is a biocide commonly used in virucidal products, and is found in urban aquatic ecosystems. The bioaccumulation of DDBAC in biofilms exposed or not to ALAN was analyzed. The responses of taxonomic composition, photosynthetic activity, and fatty acid composition of biofilms were examined. The results indicate that ALAN negatively affects photosynthetic yield and chlorophyll production of biofilms. Additionally, exposure to DDBAC at environmental concentrations induces lipid peroxidation, with an increase of oxylipins. This experimental study provides first insights on the consequences of ALAN and DDBAC for aquatic ecosystems. It also opens avenues for the identification of new biomarkers that could be used to monitor urban pollution impacts in natural environments. Our study addressed the effects of two anthropogenic threats to aquatic biodiversity in urban environments: biocide contamination (DDBAC) and artificial light at night (ALAN). ALAN is ubiquitous, affecting all aquatic environments worldwide, while DDBAC is increasingly present in urban environments. We demonstrated that ALAN affects the photosynthesis of microalgal communities and that DDBAC exposure increases oxylipin production by the biofilms, which represent basal resources of most aquatic food chains in urban environments and elsewhere. This work confirms that stressors typical of urban environments deserve more research, in particular under more realistic (natural) conditions and taking into account possible interactive effects.