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Artificial light at night (ALAN) is a recognized source of anthropogenic disturbance, although its effects on biological systems have not been fully explored. Within marine ecosystems, coastal areas are the most impacted by ALAN. Here, we focused on the Mediterranean sea urchin Paracentrotus lividus, which has a crucial role in shaping benthic ecosystems. Our objective was to investigate if ALAN affects the nocturnal locomotor behavior of P. lividus. A semi-controlled field study was conducted along a rocky shore near a promenade lit at night. Results suggested a potential impact of ALAN on the locomotor behavior of sea urchins. Individuals of P. lividus tended to move away from the light sources while its directions in dark conditions were uniform. Their locomotor performance, in presence of ALAN, was characterized by shorter latency time, lower sinuosity and higher mean speed at increasing light intensity, with potential cascading effect at the ecosystem level.

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Excessive urbanization leads to considerable nature deficiency and abundant artificial infrastructure in urban areas, which triggered intensive discussions on people's exposure to green space and outdoor artificial light at night (ALAN). Recent academic progress highlights that people's exposure to green space and outdoor ALAN may be confounders of each other but lacks systematic investigations. This study investigates the associations between people's exposure to green space and outdoor ALAN by adopting the three most used research paradigms: population-level residence-based, individual-level residence-based, and individual-level mobility-oriented paradigms. We employed the green space and outdoor ALAN data of 291 Tertiary Planning Units in Hong Kong for population-level analysis. We also used data from 940 participants in six representative communities for individual-level analyses. Hong Kong green space and outdoor ALAN were derived from high-resolution remote sensing data. The total exposures were derived using the spatiotemporally weighted approaches. Our results confirm that the negative associations between people's exposure to green space and outdoor ALAN are universal across different research paradigms, spatially non-stationary, and consistent among different socio-demographic groups. We also observed that mobility-oriented measures may lead to stronger negative associations than residence-based measures by mitigating the contextual errors of residence-based measures. Our results highlight the potential confounding associations between people's exposure to green space and outdoor ALAN, and we strongly recommend relevant studies to consider both of them in modeling people's health outcomes, especially for those health outcomes impacted by the co-exposure to them.

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Rapid urbanization of habitats alters the physical, chemical, auditory, and photic environments of human and wild animal inhabitants. One of the most widespread transformations is caused by artificial light at night (ALAN), but it is not clear the extent to which individuals acclimate to such rapid environmental change. Here, we tested the hypothesis that urban birds show increased resistance to harmful behavioral, parasitological, and physiological effects of ALAN. We captured house finches (Haemorhous mexicanus), a bird that commonly inhabits cities and their natural surroundings, from two urban and two rural sites in Phoenix, Arizona, USA, which differ by both degree of urbanization and by multiple orders of magnitude in ALAN intensity, and placed them in a common garden laboratory setting. We exposed half of the birds from each habitat type to ecologically relevant levels of night lighting during the subjective night and found that, while ALAN exposure reduced sleep in both urban and rural birds, ALAN-exposed urban birds were able to sleep longer than ALAN-exposed rural birds. We also found that ALAN exposure increased the proliferation rate of an intestinal coccidian parasite (Isospora spp.) in both urban and rural birds, but that the rate of proliferation was lower in urban relative to rural birds. We found that night lighting suppressed titers of feather corticosterone in rural but not urban birds, suggesting that light impairs HPA function through chronic stress or suppression of its circadian rhythmicity, and that urban birds were again resistant to this effect. Mediation analyses show that the effect of ALAN exposure in rural birds was significantly sleep-mediated for feather corticosterone but not coccidiosis, suggesting a diversity of mechanisms by which ALAN alters physiology. We contribute further evidence that animals from night-lit habitats can develop resistance to ALAN and its detrimental effects.

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Identifying key molecular pathways and genes involved in the response to urban pollutants is an important step in furthering our understanding of the impact of urbanisation on wildlife. The expansion of urban habitats and the associated human-introduced environmental changes are considered a global threat to the health and persistence of humans and wildlife. The present study experimentally investigates how short-term exposure to three urban-related pollutants -soot, artificial light at night (ALAN) and traffic noise-affects transcriptome-wide gene expression in livers from captive female zebra finches (Taeniopygia guttata). Compared to unexposed controls, 17, 52, and 28 genes were differentially expressed in soot, ALAN and noise-exposed birds, respectively. In soot-exposed birds, the enriched gene ontology (GO) terms were associated with a suppressed immune system such as interferon regulating genes (IRGs) and responses to external stimuli. For ALAN-exposed birds, enriched GO terms were instead based on downregulated genes associated with detoxification, redox, hormonal-, and metabolic processes. Noise exposure resulted in downregulation of genes associated with the GO terms: cellular responses to substances, catabolic and cytokine responses. Among the individually differentially expressed genes (DEGs), soot led to an increased expression of genes related to tumour progression. Likewise, ALAN revealed an upregulation of multiple genes linked to different cancer types. Both sensory pollutants (ALAN and noise) led to increased expression of genes linked to neuronal function. Interestingly, noise caused upregulation of genes associated with serotonin regulation and function (SLC6A4 and HTR7), which previous studies have shown to be under selection in urban birds. These outcomes indicate that short-term exposure to the three urban pollutants perturbate the liver transcriptome, but most often in different ways, which highlights future studies of multiple-stress exposure and their interactive effects, along with their long-term impacts for urban-dwelling wildlife.

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Artificial Light at Night (ALAN) threatens to disrupt most natural habitats and species, including those in coastal settings, where a growing number of studies have identified ALAN impacts. A careful examination of the light properties behind those impacts is important to better understand and manage the effects of this stressor. This study focused on ALAN monochromatic wavelengths and examined which types of light spectra altered the natural activity of two prominent coastal species from the Pacific southeast: the talitroid amphipod Orchestoidea tuberculata and the oniscoid isopod Tylos spinulosus. We compared the natural daylight/night activity of these organisms with the one they exhibit when exposed to five different ALAN wavelengths: lights in the violet, blue, green, amber, and red spectra. Our working hypothesis was that ALAN alters these species' activity at night, but the magnitude of such impact differs depending on light wavelengths. Measurements of activity over 24 h cycles for five consecutive days and in three separate experiments confirmed a natural circadian activity pattern in both species, with strong activity at night (∼90% of probability) and barely any activity during daylight. However, when exposed to ALAN, activity declined significantly in both species under all light wavelengths. Interestingly, amphipods exhibited moderate activity (∼40% of probability) when exposed to red lights at night, whereas isopods shifted some of their activity to daylight hours in two of the experiments when exposed to blue or amber lights, suggesting a possible alteration in this species circadian rhythm. Altogether, our results were consistent with our working hypothesis, and suggest that ALAN reduces night activity, and some wavelengths have differential effects on each species. Differences between amphipods and isopods are likely related to their distinct adaptations to natural low-light habitat conditions, and therefore distinct sensitivity to ALAN.

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The growth of human activity and infrastructure has led to an unprecedented rise in the use of Artificial Light at Night (ALAN) with demonstrable impacts on ecological communities and ecosystem services. However, there remains very little information on how ALAN interacts with or obscures light from celestial bodies, which provide vital orientating cues in a number of species. Furthermore, no studies to date have examined how climatic conditions such as cloud cover, known to influence the intensity of skyglow, interact with lunar irradiance and ALAN over the course of a lunar cycle to alter migratory abilities of species. Our night-time field study aimed to establish how lunar phase and climatic conditions (cloud cover) modulate the impact of ALAN on the abundance and migratory behaviour of Talitrus saltator, a key sandy beach detritivore which uses multiple light associated cues during nightly migrations. Our results showed that the number and size of individuals caught decreased significantly as ALAN intensity increased. Additionally, when exposed to ALAN more T. saltator were caught travelling parallel to the shoreline, indicating that the presence of ALAN is inhibiting their ability to navigate along their natural migration route, potentially impacting the distribution of the population. We found that lunar phase and cloud cover play a significant role in modifying the impact of ALAN, highlighting the importance of incorporating natural light cycles and climatic conditions when investigating ALAN impacts. Critically we demonstrate that light levels as low as 3 lx can have substantial effects on coastal invertebrate distributions. Our results provide the first evidence that ALAN impacted celestial migration can lead to changes to the distribution of a species.

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Artificial light at night (ALAN) negatively impacts organisms in many ways, from their feeding behaviors to their response and ability to deal with disease. Our knowledge of ALAN is focused on hosts, but we must also consider their parasites, which constitute half of all described animal species. Here, we assessed the impact of light exposure on a model host-parasite system (Poecilia reticulata and the ectoparasitic monogenean Gyrodactylus turnbulli). First, parasite-free fish were exposed to 12:12 h light:dark (control) or 24:0 h light:dark (ALAN) for 21 days followed by experimental infection. Second, naturally acquired G. turnbulli infections were monitored for 28 days during exposure of their hosts to a specified light regime (6:18 h, 12:12 h, or 24:0 h light:dark). Experimentally infected fish exposed to constant light had, on average, a greater maximum parasite burden than controls, but no other measured parasite metrics were impacted. Host feeding behavior was also significantly affected: fish under ALAN fed faster and took more bites than controls, whilst fish exposed to reduced light fed slower. Thus, ALAN can impact parasite burdens, even in the short term, and altering light conditions will impact fish feeding behavior. Such responses could initiate disease outbreaks or perturb food-webs with wider ecological impacts.

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Artificial light at night (ALAN) is a global change driver but how it interacts with plant invasions is unclear. Determining this requires understanding direct effects of ALAN on physiology, phenology, growth, and fitness of both invasive and native plant species and its indirect effects mediated through mutualistic and/or antagonistic interactions.

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Artificial Light at Night (ALAN) has been identified as a primary driver of environmental change in the 21st century with key impacts on ecosystems. At the same time, developments of LED lighting systems with adjustable parameters-such as color temperature and light intensity-may provide an opportunity to mitigate the negative effects of ALAN. To test the potential effects of LED properties, we conducted a comprehensive field study over two summers at three forest sites in Switzerland. We investigated the impact of three key attributes of LED lights (color temperature, brightness, and luminaire shape) on the abundance and community structure of ground-dwelling invertebrate functional groups (predators, omnivores, and detritivores). We found a significantly increased nocturnal attraction of omnivores (+275%) and predators (+70%), but not detritivores, to ALAN, altering arthropod community composition and trophic interactions in forests. LED color temperature and luminaire shape showed minimal effects on all three functional groups, while reducing light level from 100% to 50% attracted fewer individuals in all groups with a significant effect in omnivores (-57%). In addition, we observed significant interactions of color temperatures and luminaire shapes with light intensity, with a decrease in numbers when dimming the light to 50% intensity combined with a color temperature of 3700 K for predators (-53%), with diffusing luminaire shapes for omnivores (-77%) and with standard luminaire shape for detritivores (-27%). The predator-detritivore ratio showed a significant color temperature - light level interaction, with increased numbers of predators around streetlights with 3700 K and 100% intensity, resulting in an elevated top-down pressure on detritivores. These results suggest the importance of considering combined light characteristics in future outdoor lighting designs.

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Urban ecosystems are subjected to multiple anthropogenic stresses, which impact aquatic communities. Artificial light at night (ALAN) for instance can significantly alter the composition of algal communities as well as the photosynthetic cycles of autotrophic organisms, possibly leading to cellular oxidative stress. The combined effects of ALAN and chemical contamination could increase oxidative impacts in aquatic primary producers, although such combined effects remain insufficiently explored. To address this knowledge gap, a one-month experimental approach was implemented under controlled conditions to elucidate effects of ALAN and dodecylbenzyldimethylammonium chloride (DDBAC) on aquatic biofilms. DDBAC is a biocide commonly used in virucidal products, and is found in urban aquatic ecosystems. The bioaccumulation of DDBAC in biofilms exposed or not to ALAN was analyzed. The responses of taxonomic composition, photosynthetic activity, and fatty acid composition of biofilms were examined. The results indicate that ALAN negatively affects photosynthetic yield and chlorophyll production of biofilms. Additionally, exposure to DDBAC at environmental concentrations induces lipid peroxidation, with an increase of oxylipins. This experimental study provides first insights on the consequences of ALAN and DDBAC for aquatic ecosystems. It also opens avenues for the identification of new biomarkers that could be used to monitor urban pollution impacts in natural environments.

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Artificial Light At Night (ALAN) is a major urban perturbation, which can have detrimental effects on wildlife. Recent urban planning has led to an increased use of white light emission diodes (LEDs) in cities. However, little is known about the effects of this type of ALAN on wild vertebrates, especially during reproduction. We designed an experiment to test the impact of ALAN on the activity rhythms (daily time of first activity (TFA) and time of last activity (TLA)) of captive House sparrows (Passer domesticus) during several reproductive stages (from pre-breeding to post-breeding). We also tested the impact of ALAN on reproductive performance (laying date, clutch size, hatching and fledging success). Experimental birds were active earlier in the morning (earlier TFA) relative to controls although experimental and control birds did not differ in their TLA. The effect of ALAN on TFA was apparent during specific stages only (pre-breeding and chick-rearing stages), suggesting that sparrows actively adjust their activity in response to ALAN only during specific periods. This impact of ALAN on activity did not persist through the whole breeding season, suggesting that sparrows may habituate to ALAN. Alternatively, they may not be able to sustain a long-term increased activity in response to ALAN because of sleep deprivation and related physiological costs. Finally, we did not find any impact of ALAN on the reproductive performance of captive house sparrows held under optimal conditions. This suggests that ALAN may not be dramatically detrimental to the reproduction of this urban exploiter, at least when food availability is not constraining.

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Aquatic ecosystems and their communities are exposed to numerous stressors of various natures (chemical and physical), whose impacts are often poorly documented. In urban areas, the use of biocides such as dodecyldimethylbenzylammonium chloride (DDBAC) and their subsequent release in wastewater result in their transfer to urban aquatic ecosystems. DDBAC is known to be toxic to most aquatic organisms. Artificial light at night (ALAN) is another stressor that is increasing globally, especially in urban areas. ALAN may have a negative impact on photosynthetic cycles of periphytic biofilms, which in turn may result in changes in their metabolic functioning. Moreover, studies suggest that exposure to artificial light could increase the biocidal effect of DDBAC on biofilms. The present study investigates the individual and combined effects of DDBAC and/or ALAN on the functioning and structure of photosynthetic biofilms. We exposed biofilms in artificial channels to a nominal concentration of 30 mg.L-1 of DDBAC and/or ALAN for 10 days. ALAN modified DDBAC exposure, decreasing concentrations in the water but not accumulation in biofilms. DDBAC had negative impacts on biofilm functioning and structure. Photosynthetic activity was inhibited by > 90% after 2 days of exposure, compared to the controls, and did not recover over the duration of the experiment. Biofilm composition was also impacted, with a marked decrease in green algae and the disappearance of microfauna under DDBAC exposure. The integrity of algal cells was compromised where DDBAC exposure altered the chloroplasts and chlorophyll content. Impacts on autotrophs were also observed through a shift in lipid profiles, in particular a strong decrease in glycolipid content was noted. We found no significant interactive effect of ALAN and DDBAC on the studied endpoints.

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Natural experiments provide remarkable opportunities to test the large-scale effects of human activities. Widespread energy blackouts offer such an 'experiment' to test the impacts of artificial light at night (ALAN) on wildlife. We use the situation in South Africa, where regular scheduled blackouts are being implemented, to highlight this opportunity.

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This appreciation of the work of Alan Roland reviews his pioneering contributions to the field of cross-cultural psychoanalysis based on the clinical experience with patients from non-Western cultures, most notably India and Japan.

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BACKGROUND: Recently, the effect of artificial light at night (ALAN) on the physiology and behavior of insects has gradually attracted the attention of researchers and has become a new research topic. Aedes albopictus is an important vector that poses a great public health risk. Further studies on the diapause of Ae. albopictus can provide a basis for new vector control, and it is also worth exploring whether the effect of ALAN on the diapause of Ae. albopictus will provide a reference for the prevention and control of infectious diseases mediated by Ae. albopictus. METHODS: In this study, we experimentally studied the diapause characteristics of different geographical strains of Ae. albopictus under the interference of ALAN, explored the effect of ALAN on the diapause of Ae. albopictus and explored the molecular mechanism of ALAN on the diapause process through RNA-seq. RESULTS: As seen from the diapause incidence, Ae. albopictus of the same geographic strain showed a lower diapause incidence when exposed to ALAN. The differentially expressed genes (DEGs) were mainly enriched in signaling and metabolism-related pathways in the parental females and diapause eggs of the ALAN group. CONCLUSIONS: ALAN inhibits Ae. albopictus diapause. In the short photoperiod induced diapause of Ae. albopictus in temperate strain Beijing and subtropical strain Guangzhou, the disturbance of ALAN reduced the egg diapause rate and increased the egg hatching rate of Ae. albopictus, and the disturbance of ALAN also shortened the life cycle of Ae. albopictus eggs after hatching.

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Light is the most important Zeitgeber for temporal synchronization in nature. Artificial light at night (ALAN) disrupts the natural light-dark rhythmicity and thus negatively affects animal behavior. However, to date, ALAN research has been mostly conducted under laboratory conditions in this context. Here, we used the field cricket, Gryllus bimaculatus, to investigate the effect of ALAN on insect behavior under semi-natural conditions, i.e., under shaded natural lighting conditions, natural temperature and soundscape. Male crickets were placed individually in outdoor enclosures and exposed to ALAN conditions ranging from <0.01 to 1500 lx intensity. The crickets' stridulation behavior was recorded for 14 consecutive days and nights and their daily activity patterns were analysed. ALAN impaired the crickets' stridulation rhythm, evoking a change in the crickets' naturally synchronized daily activity period. This was manifested by a light-intensity-dependent increase in the proportion of insects demonstrating an intrinsic circadian rhythm (free-run behavior). This also resulted in a change in the population's median activity cycle period. These ALAN-induced effects occurred despite the crickets' exposure to almost natural conditions. Our findings provide further validity to our previous studies on ALAN conducted under lab conditions and establish the deleterious impacts of ALAN on animal behavioral patterns. TEASER: Artificial light at night alters cricket behavior and desynchronizes their stridulation even under near-natural conditions.

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Moths and other insects are attracted by artificial light sources. This flight-to-light behaviour disrupts their general activity focused on finding resources, such as mating partners, and increases predation risk. It thus has substantial fitness costs. In illuminated urban areas, spindle ermine moths Yponomeuta cagnagella were reported to have evolved a reduced flight-to-light response. Yet, the specific mechanism remained unknown, and was hypothesized to involve either changes in visual perception or general flight ability or overall mobility traits. Here, we test whether spindle ermine moths from urban and rural populations-with known differences in flight-to-light responses-differ in flight-related morphological traits. Urban individuals were found to have on average smaller wings than rural moths, which in turn correlated with a lower probability of being attracted to an artificial light source. Our finding supports the reduced mobility hypothesis, which states that reduced mobility in urban areas is associated with specific morphological changes in the flight apparatus.

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Biological clocks are evolved time-keeping systems by which organisms rhythmically coordinate physiology within the body, and align it with rhythms in their environment. Clocks are highly sensitive to light and are at the interface of several major endocrine pathways. Worryingly, exposure to artificial-light-at-night (ALAN) is rapidly increasing in ever more extensive parts of the world, with likely impact on wild organisms mediated by endocrine-circadian pathways. In this overview, we first give a broad-brush introduction to biological rhythms. Then, we outline interactions between the avian clock, endocrine pathways, and environmental and internal modifiers. The main focus of this review is on the circadian hormone, melatonin. We summarize information from avian field and laboratory studies on melatonin and its relationships with behaviour and physiology, including often neglected developmental aspects. When exposed to ALAN, birds are highly vulnerable to disruption of behavioural rhythms and of physiological systems under rhythmic control. Several studies suggest that melatonin is likely a key mediator for a broad range of effects. We encourage further observational and experimental studies of ALAN impact on melatonin, across the full functional range of this versatile signalling molecule, as well as on other candidate compounds at the endocrine-circadian interface. This article is part of the theme issue 'Endocrine responses to environmental variation: conceptual approaches and recent developments'.

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Environmental variation in the Anthropocene involves several factors that interfere with endocrine systems of wildlife and humans, presenting a planetary boundary of still unknown dimensions. Here, we focus on chemical compounds and other impacts of anthropogenic and natural origins that are adversely affecting reproduction and development. The main sink of these endocrine disruptors (EDs) is surface waters, where they mostly endanger aquatic vertebrates, like teleost fish and amphibians. For regulatory purposes, EDs are categorized into EATS modalities (oestrogenic, androgenic, thyroidal, steroidogenesis), only addressing endocrine systems being assessable by validated tests. However, there is evidence that non-EATS modalities-and even natural sources, such as decomposition products of plants or parasitic infections-can affect vertebrate endocrine systems. Recently, the disturbance of natural circadian light rhythms by artificial light at night (ALAN) has been identified as another ED. Reviewing the knowledge about EDs affecting teleosts and amphibians leads to implications for risk assessment. The generally accepted WHO-definition for EDs, which focuses exclusively on 'exogenous substances' and neglects parasitic infections or ALAN, seems to require some adaptation. Natural EDs have been involved in coevolutionary processes for ages without resulting in a general loss of biodiversity. Therefore, to address the 'One Health'-principle, future research and regulatory efforts should focus on minimizing anthropogenic factors for endocrine disruption. This article is part of the theme issue 'Endocrine responses to environmental variation: conceptual approaches and recent developments'.

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This study examines the impact of Artificial Light at Night (ALAN) on two coral species, Acropora eurystoma and Pocillopora damicornis, in the Gulf of Aqaba/Eilat Red Sea, assessing their natural isotopic responses to highlight changes in energy and nutrient sourcing due to sensory light pollution. Our findings indicate significant disturbances in photosynthetic processes in Acropora eurystoma, as evidenced by shifts in δ13C values under ALAN, pointing to alterations in carbon distribution or utilization. In Pocillopora damicornis, similar trends were observed, with changes in δ13C and δ15N values suggesting a disruption in its nitrogen cycle and feeding strategies. The study also uncovers species-specific variations in heterotrophic feeding, a crucial factor in coral resilience under environmental stress, contributing to the corals' fixed carbon budget. Light measurements across the Gulf demonstrated a gradient of light pollution which possess the potential of affecting marine biology in the region. ALAN was found to disrupt natural diurnal tentacle behaviors in both coral species, crucial for prey capture and nutrient acquisition, thereby impacting their isotopic composition and health. Echoing previous research, our study underscores the need to consider each species' ecological and physiological contexts when assessing the impacts of anthropogenic changes. The findings offer important insights into the complexities of marine ecosystems under environmental stress and highlight the urgency of developing effective mitigation strategies.

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