11th Symposium for European Freshwater Sciences

Author(s) Alphabetically:

Susanne STEPHAN¹; Maria SEGOVIA²; Andreas JECHOW³; Jens C. NEJSTGAARD¹; Christopher KYBA⁴; Gabriel SINGER³; Víctor VAZQUEZ²; Tim WALLES¹; Franziska KUPPRAT³; Franz HÖLKER³; Mark O. GESSNER¹; Stella A. BERGER¹; ILES CONSORTIUM

Abstract:

Light plays a key role in structuring biological communities. Since the 19^th century, anthropogenic light emission from Earth has increased massively, disrupting the natural cycle of light and darkness. In addition to direct illumination such as from street lighting, ecosystems can experience light pollution even in remote areas when light that is backscattered to Earth by the atmosphere, generates so-called skyglow. Little is known about the effects of skyglow on aquatic ecosystems and phytoplankton in particular. We therefore conducted a large-scale enclosure experiment in summer 2016 to investigate effects of skyglow on a natural plankton community of a lake located in one of the darkest areas of Central Europe. White light emitting diodes (LEDs) installed above the enclosures emitted diffuse light at three different intensities (0, 0.06 and 6 lux) onto the water surface. Responses of phytoplankton in the epilimnion were recorded for 7 weeks at weekly intervals. Results indicate that skyglow affects primary production and biomass as well as phytoplankton physiology in terms of thylakoidal electron transport rate (ETR) and cell viability. Epilimnetic production rates of phytoplankton and biomass measured as chlorophyll a were reduced under high skyglow, whereas ETR and cell viability responded to both high and low levels of skyglow. These results show that exposure to even low light levels at night can affect aquatic primary producers, suggesting an urgent need to understand direct and indirect responses of plankton communities to light pollution by skyglow.

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