Impacts of urban stressors on freshwater biofilms

Vrba, R.; Lavoie, I.; Creusot, N.; Eon, M.; Millan-Navarro, D.; Feurtet-Mazel, A.; Mazzella, N.; Moreira, A.; Planas, D.; Morin, S.

doi:10.1101/2023.06.11.544504

bioRxiv · 10.1101/2023.06.11.544504

Impacts of urban stressors on freshwater biofilms

Vrba, R.·Lavoie, I.·Creusot, N.·Eon, M.·Millan-Navarro, D.·Feurtet-Mazel, A.·Mazzella, N.·Moreira, A.·Planas, D.·Morin, S.

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Abstract

Aquatic ecosystems and their communities are exposed to numerous stressors of various natures (chemical and physical), which impacts are often poorly documented. In urban areas, the use of biocides such as dodecyldimethylbenzylammonium chloride (DDBAC) and their subsequent release in wastewater result in their transfer to urban aquatic ecosystems. DDBAC is known to be toxic to most aquatic organisms. Artificial light at night (ALAN) is another stressor that is increasing globally, especially in urban areas. ALAN may have a negative impact on photosynthetic cycles of periphytic biofilms, which in turn may result in changes in their metabolic functioning. Moreover, studies suggest that exposure to artificial light could increase the biocidal effect of DDBAC on biofilms. The present study investigates the individual and combined effects of DDBAC and/or ALAN on the functioning and structure of photosynthetic biofilms. We exposed biofilms in artificial channels to a nominal concentration of 30 mg.L-1 of DDBAC and/or ALAN for 10 days. ALAN modified DDBAC exposure, decreasing concentrations in the water but not accumulation in biofilms. DDBAC had negative impacts on biofilm functioning and structure. Photosynthetic activity was inhibited by > 90% after 2 days of exposure, compared to the controls, and did not recover over the duration of the experiment. Biofilm composition was also impacted, with a marked decrease in green algae and the disappearance of microfauna under DDBAC exposure. The integrity of algal cells was compromised where DDBAC exposure altered the chloroplasts and chlorophyll content. Impacts on autotrophs were also observed through a shift in lipid profiles, in particular a strong decrease in glycolipid content was noted. We found no significant interactive effect of ALAN and DDBAC on the studied endpoints. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=47 SRC="FIGDIR/small/544504v2_ufig1.gif" ALT="Figure 1"> View larger version (13K): org.highwire.dtl.DTLVardef@15e217borg.highwire.dtl.DTLVardef@e81f3forg.highwire.dtl.DTLVardef@15b9c08org.highwire.dtl.DTLVardef@1610534_HPS_FORMAT_FIGEXP M_FIG C_FIG

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Vrba, R., Lavoie, I., Creusot, N., Eon, M., Millan-Navarro, D., Feurtet-Mazel, A., Mazzella, N., Moreira, A., Planas, D., Morin, S.. 2023-06-11. Impacts of urban stressors on freshwater biofilms. https://doi.org/10.1101/2023.06.11.544504

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