Artificial light at night (ALAN) causes variable dose-responses in a sandy beach isopod

Jan 21, 2022Environmental science and pollution research international

Artificial light at night causes different dose-related responses in a sandy beach isopod

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Abstract

Increasing artificial light intensity at night resulted in a ~threefold decline in RNA:DNA ratios and a ~threefold increase in absorption efficiency in the isopod Tylos spinulosus.

Different light intensities were tested: 0 (control), 20, 40, 60, 80, and 100 lx.
RNA:DNA ratios decreased significantly with higher light intensity, indicating reduced fitness condition.
Absorption efficiency increased with light intensity, suggesting a compensatory mechanism for nutrient intake.
Non-linear analysis indicated potential thresholds for RNA:DNA ratios at 80 lx and absorption efficiency at 40 lx.
Isopod growth rates remained unchanged despite varying light intensities.

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Artificial Light at Night (ALAN) is expanding worldwide, and the study of its influence remains limited mainly to documenting impacts, overlooking the variation in key characteristics of the artificial light such as its intensity. The potential dose-response of fitness-related traits to different light intensities has not been assessed in sandy beach organisms. Hence, this study explored dose-responses to ALAN by exposing the intertidal sandy beach isopod Tylos spinulosus to a range of light intensities at night: 0 (control), 20, 40, 60, 80 and 100 lx. We quantified the response of this species at the molecular (RNA:DNA ratios), physiological (absorption efficiency) and organismal (growth rate) levels. Linear and non-linear regressions were used to explore the relationship between light intensity and the isopod response. The regressions showed that increasing light intensity caused an overall ~ threefold decline in RNA:DNA ratios and a ~ threefold increase in absorption efficiency, with strong dose-dependent effects. For both response variables, non-linear regressions also identified likely thresholds at 80 lx (RNA:DNA) and 40 lx (absorption efficiency). By contrast, isopod growth rates were unrelated (unaltered) by the increase in light intensity at night. We suggest that ALAN is detrimental for the condition of the isopods, likely by reducing the activity and feeding of these nocturnal organisms, and that the isopods compensate this by absorbing nutrients more efficiently in order to maintain growth levels.

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Artificial light at night (ALAN) causes variable dose-responses in a sandy beach isopod

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