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Spectral composition of light pollution affects melatonin suppression and West Nile virus infection resistance and mortality in the House Sparrow (Passer domesticus).

Citation

Kernbach, Meredith; Cassone, Vincent; Unnasch, Thomas; Martin, Lynn (2021), Spectral composition of light pollution affects melatonin suppression and West Nile virus infection resistance and mortality in the House Sparrow (Passer domesticus)., Dryad, Dataset, https://doi.org/10.5061/dryad.r7sqv9s89

Abstract

Artificial light at night (ALAN) has become a pervasive anthropogenic stressor for both humans and wildlife. Although many negative impacts of ALAN on human health have been identified, the consequences for infectious disease dynamics are largely unexplored. With the increase in popularity of energy efficient light-emitting diodes (LEDs), the effects of spectral composition of ALAN have also come into question. Previous studies showed that exposure to low levels of incandescent ALAN extended the infectious period of House Sparrows infected with West Nile virus (WNV) without affecting mortality rates, thus increasing the pathogen initial reproductive rate (R0) by about 41%. Here, we asked whether exposure to broad-spectrum (3000K [Kelvin; unit of color temperature]) ALAN suppressed melatonin, a hormone implicated in ALAN-induced physiological consequences, in House Sparrows (Passer domesticus). We then asked whether amber-hue bulbs (1800K) could ameliorate the effects of WNV on individual sparrows, and whether broad-spectrum or blue-rich bulbs (3000K and 5000K, respectively) could exacerbate them. We found that exposure to low intensity (~5 lux) broad-spectrum (3000K) ALAN significantly suppressed melatonin levels throughout the night. Second, we found that exposure to broad-spectrum and blue-rich (3000+5000K) lights did not affect WNV viremia but did increase WNV-induced mortality. Conversely, birds exposed to amber-hue (1800K) ALAN had lower viremia and mortality rates similar to controls (i.e., natural light conditions). This study demonstrates that ALAN affects melatonin regulation in birds, but this effect, as well as ALAN influences on infectious disease responses, can be ameliorated by particular lighting technologies.

Funding

National Science Foundation, Award: 1257773