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Hölker, F., Wurzbacher, C., Weißenborn, C., Monaghan, M. T., Holzhauer, S. I. J., & Premke, K. (2015). Microbial diversity and community respiration in freshwater sediments influenced by artificial light at night. Philos Trans R Soc Lond B Biol Sci, 370, 20140130.
Abstract: An increasing proportion of the Earth's surface is illuminated at night. In aquatic ecosystems, artificial light at night (ALAN) may influence microbial communities living in the sediments. These communities are highly diverse and play an important role in the global carbon cycle. We combined field and laboratory experiments using sediments from an agricultural drainage system to examine how ALAN affects communities and alters carbon mineralization. Two identical light infrastructures were installed parallel to a drainage ditch before the start of the experiment. DNA metabarcoding indicated that both sediment communities were similar. After one was lit for five months (July–December 2012) we observed an increase in abundance (diatoms, Cyanobacteria) in ALAN-exposed sediments. In laboratory incubations mimicking summer and winter (six weeks each), communities in sediments that were exposed to ALAN for 1 year (July 2012–June 2013) showed less overall seasonal change compared with ALAN-naive sediments. Nocturnal community respiration was reduced in ALAN-exposed sediments. In long-term exposed summer-sediments, we observed a shift from negative to positive net ecosystem production. Our results indicate ALAN may alter sediment microbial communities over time, with implications for ecosystem-level functions. It may thus have the potential to transform inland waters to nocturnal carbon sinks.
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Maggi, E., Bongiorni, L., Fontanini, D., Capocchi, A., Dal Bello, M., Giacomelli, A., et al. (2020). Artificial light at night erases positive interactions across trophic levels. Funct Ecol, 34(3), 694–706.
Abstract: 1. Artificial light at night (ALAN) is one of the most recently recognized sources of anthropogenic disturbance, with potentially severe effects on biological systems that are still to be fully explored. Among marine ecosystems, high‐shore habitats are those more likely to be impacted by ALAN, due to a more intense exposition to outdoor nocturnal lightings (mostly from lamps along coastal streets and promenades, or within harbours, ports and marinas).
2. By performing in situ nocturnal manipulations of a direct source of white LED light and presence of herbivores in a Mediterranean high‐shore habitat, we assessed the interactive effects of light pollution and grazing on two key functional components of the epilithic microbial community (the cyanobacteria, as the main photoautotrophic component, and the other bacteria, mainly dominated by heterotrophs) developing on rocky shores.
3. Results showed an unexpected increase in the diversity of epilithic bacterial biofilm at unlit sites in the presence of grazers, that was more evident on the other (mainly heterotrophic) bacterial component, when giving weight to more abundant families. This effect was likely related to the mechanical removal of dead cells through the grazing activity of consumers. ALAN significantly modified this scenario, by reducing the density of grazers and thus erasing their effects on bacteria, and by increasing the diversity of more abundant cyanobacterial families.
4. Overall, direct and indirect effects on ALAN resulted in a significant increase in the diversity of the photoautotrophic component and a decrease in the heterotrophic one, likely affecting key ecosystem functions acting on rocky shore habitats.
5. ALAN may represent a threat for natural systems through the annihilation of positive interactions across trophic levels, potentially impairing the relationship between biodiversity and functioning of ecosystems and interacting with other global and local stressors currently impinging on coastal areas.
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Poulin, C., Bruyant, F., Laprise, M. - H., Cockshutt, A. M., Marie-Rose Vandenhecke, J., & Huot, Y. (2014). The impact of light pollution on diel changes in the photophysiology of Microcystis aeruginosa. Journal of Plankton Research, 36(1), 286–291.
Abstract: Assessing the effect of light pollution, Microcystis aeruginosa was grown with and without low levels of night lighting. Significant differences were observed between the treatments in the maximum quantum yield of charge separation, the intracellular chlorophyll a concentration, the functional absorption cross-section of photosystem II, the number of Rubisco per cell and per chlorophyll a, the number of photosystem I per chlorophyll a, and the chlorophyll a fraction not bound to the photosystems and IsiA.
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