Night Lights Reshape Ecosystems

Night lights affect two marine crustaceans differently, helping explain which species will be found in which portion of Tokyo Bay, Japan, according to a study. Artificial light at night can affect the behavior, physiology, and ecological distribution of marine species. Daiki Sato sought to explore the effects of city lights on the ecosystem of Tokyo Bay, one of the world's most intensely illuminated coastal regions. Sato specifically focused on two closely related nocturnal isopods, Ligia furcata and Ligia laticarpa. Sato used genetic analysis, remote sensing, and Bayesian modeling, as well as behavioral experiments on the isopods in the lab. L. laticarpa occurrence in the bay was correlated with higher nighttime light intensity, and L. furcata showed reduced activity when reared under artificial lights at night, while L. laticarpa was largely unaffected by night lights. Night lights can structure ecosystems by filtering out species that cannot tolerate the light, leaving the ecosystem to those species that can—and act as a barrier between lineages, potentially reducing gene flow between them. According to the author, the findings add to growing evidence that human activity is meaningfully shaping evolution and likely favoring lineages with high developmental plasticity in sensory and circadian systems in human-altered environments.