Artificial light at night alters the activity and feeding behaviour of sandy beach amphipods and pose a threat to their ecological role in Atlantic Canada

Ecological alterations of promenade lighting on crustacean assemblage: A real-scale study

Coastal shallow habitats are greatly exposed to artificial light at night (ALAN). Although the ecological impacts of light pollution have been tested in some marine species, few studies have been conducted at assemblage level. Our study is a real-scale approach to the effects of ALAN from seaside promenade lighting to the crustacean assemblage of the water column. Beach lighting of a coastal town remained on and off and samples were collected both at night and day on each scenario. There was a significant biomass reduction in certain crustacean taxa in ALAN presence. Moreover, some species were particularly sensitive to light pollution, such as the copepod Acartia (Acartiura) clausi or the mysid Mesopodopsis slabberi. Changes in crustacean parameters were detected although nights with the lighting on and off were very close, highlighting the potential recovery capacity. These results are proposed for light pollution management in coastal shallow habitats dominated by crustaceans.

Artificial Light at Night (ALAN) alters the behavior and physiology of a sandy beach isopod. Are these effects reversible?

Artificial Light at Night (ALAN) is becoming a pervasive stressor in both terrestrial and marine habitats, posing a threat to species whose behavior and physiology rely on natural light/dark cycles. While numerous studies have examined the biological impacts of ALAN, far fewer have investigated the ability of organisms to recover from this stressor. This study used the sandy beach isopod Tylos spinulosus as a model species to assess the short-term effects of ALAN and its potential recovery following the removal of light sources. To achieve this, we conducted separate laboratory experiments to evaluate changes in locomotor activity, food consumption, food absorption efficiency, and growth rates under ALAN exposure and during recovery. We defined recovery as the state in which the measured responses statistically returned to control levels after deviating from those recorded for the same individuals under ALAN conditions. The results showed that ALAN had a detrimental effect on all four variables. While food consumption and growth returned to control levels after ALAN removal, activity and absorption efficiency did not, indicating a lack of recovery within the timeframe of the trials. These results suggest that the recovery of this species from short-term light pollution exposure is heavily dependent on the behavioral or physiological responses under examination. Hence, a broader range of responses over longer-term experiments are suggested to better understand the ability of this species to recover from light pollution at time scales relevant to management.

Redefining the photic zone: beyond the autotroph-centric view of light in the ocean

Traditional measures of the photic zone have remained focused on autotrophs, limiting understanding of how changing marine lightscapes impact heterotrophs that use light as a resource or an environmental cue. We propose a new photic zone definition that encompasses all biological processes influenced by celestial light, and a new measure of photic zone depth, the minimum light intensity that elicits biological responses. This approach allows photic zone measures to be inclusive of all marine photobiology driven by sunlight, moonlight, or starlight, and enables urgently needed exploration of the nature, extent and ecological implications of changing marine lightscapes.

Impacts of Artificial Light at Night (ALAN) on coastal ecosystems: A study on the herbivore Ampithoe valida with focus on sex-dependent responses

Artificial Light at Night is recognized for its impact on various ecosystems, with coastal areas being particularly vulnerable. While a growing number of studies have identified Artificial Light at Night's impacts on species inhabiting these ecosystems, a critical gap is the limited attention that has been given to intraspecific variability in response to this stressor. This study focused on the sex-dependent influence of Artificial Light at Night on food consumption rates and absorption efficiency in males and females of the non-indigenous amphipod Ampithoe valida. Males and females were exposed to two light treatments: a natural light/dark cycle and Artificial Light at Night. Our hypothesis was that Artificial Light at Night alters the amphipod's food consumption rates and absorption efficiency, but the magnitude of these impacts is sex-dependent. Results showed that females had higher nocturnal food consumption rates under control conditions, while males showed no significant diel food consumption rates. Under Artificial Light at Night conditions, females experienced a substantial reduction in nighttime food consumption rates and absorption efficiency, suggesting stress or disrupted circadian rhythms. In contrast, males increased their nighttime food consumption rates under Artificial Light at Night, possibly exploiting a new light-induced niche. These findings highlight the need for further research on the ecological consequences of intraspecific variation in the responses to Artificial Light at Night, particularly regarding the management and conservation of ecosystems impacted by non-indigenous species.

Crustacean photoreceptor damage and recovery: Applying a novel scanning electronic microscopy protocol in artificial light studies

Artificial light at night is a worldwide expanding form of pollution. Studies evaluating the effects of artificial light at night have often overlooked their impact on the photoreceptor, the basic functional structure of animals to absorb light. This is essential to understand the mechanisms by which this stressor may be impacting species. This study examined the photoreceptor (rhabdom) of two sandy beach crustaceans exhibiting different light tolerances at night: the amphipod Orchestoidea tuberculata and the isopod Tylos spinulosus. We developed a novel protocol to measure these species' photoreceptor areas and quantify the damage caused by artificial light at night using histological sections and scanning electron microscopy. In the isopod, a species naturally adapted to lower light intensities at night than the amphipod, the rhabdom surface was 20-times larger, and presented a tapetum, an adaptive feature found in species living in low light conditions. A brief exposure to artificial light caused 3-6 times more damage in the isopod's rhabdom. In fact, the light caused structural damage in the isopod's rhabdom but not in the amphipod's rhabdom, with no signs of recovery after 1 and 24 h. These findings suggest that the damage induced by artificial light at night on an organism's photoreceptors is more severe and persistent in species naturally adapted to lower light levels at night. Hence, this type of sensory ecological stressor may act as a novel selection pressure on these species, a concern with wide implications given the ubiquity among animals of the photoreceptor structure and its response to light.

The impacts of artificial light at night (ALAN) spectral composition on key behavioral traits of a sandy beach isopod

Artificial light at night (ALAN) is a widespread human-induced disturbance, whose effects have been documented in many ecosystems. However, limited attention has been given to the source of the lights behind ALAN, so this study examined three of them: High-Pressure Sodium (HPS) lamps and warm and cool white Light-Emitting Diodes (LEDs). Laboratory experiments compared the effects of each type of light to natural day/night conditions, upon the activity, feeding behavior and growth of the isopod Tylos spinulosus. Tanks equipped with actographs monitored locomotor activity, while separate tanks were utilized to assess food consumption and growth under natural and ALAN conditions. Our results show that all ALAN sources disrupt and reduce isopods' activity and feeding behavior, with cool and warm LEDs being the most severe and mildest, respectively. Instead, ALAN had only minor effects on isopod growth. Our findings suggest that warm LEDs may be preferable for ALAN mitigation purposes.

Artificial light and cloud cover interact to disrupt celestial migrations at night

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.

The impact of artificial light pollution at night on the life history parameters of rotifer Brachionus plicatilis with different food experiences

Artificial light at night (ALAN) may pose threat to rotifer Brachionus plicatilis. Additionally, the food of rotifer, i.e. algal community composition, often fluctuates. Thus, we selected five wavelengths of ALAN (purple, blue, green, red, white) and a three-colored light flashing mode (3-Flash) to test their impacts on life history traits of B. plicatilis with different food experiences, including those feeding Chlorella vulgaris (RC) or Phaeocystis globosa (RP). Results indicated purple ALAN promoted RC development, white ALAN inhibited RC development, while 3-Flash and white ALAN promoted RP development. Under red and white ALAN, RP increased fecundity but decreased lifespan. High-quality food enhanced rotifer's resistance to the impact of ALAN on lifespan. ALAN and food experience interacted on B. plicatilis. The effect of blue ALAN has less negative effects on B. plicatilis, based on hierarchical cluster analysis. Such findings are helpful to evaluate the potential impact of ALAN on marine zooplankton.

Splitting light pollution: Wavelength effects on the activity of two sandy beach species

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.

Artificial light at night alters the feeding activity and two molecular indicators in the plumose sea anemone Metridium senile (L.)

Artificial light at night (ALAN) is becoming a widespread stressor in coastal ecosystems, affecting species that rely on natural day/night cycles. Yet, studies examining ALAN effects remain limited, particularly in the case of sessile species. This study assessed the effects of ALAN upon the feeding activity and two molecular indicators in the widespread plumose sea anemone Metridium senile. Anemones were exposed to either natural day/night or ALAN conditions to monitor feeding activity, and tissue samples were collected to quantify proteins and superoxide dismutase (SOD) enzyme concentrations. In day/night conditions, sea anemones showed a circadian rhythm of activity in which feeding occurs primarily at night. This rhythm was altered by ALAN, which turned it into a reduced and more uniform pattern of feeding. Consistently, proteins and SOD concentrations were significantly lower in anemones exposed to ALAN, suggesting that ALAN can be harmful to sea anemones and potentially other marine sessile species.

Artificial Light at Night (ALAN) causes size-dependent effects on intertidal fish decision-making

Artificial Light at Night (ALAN) alters cycles of day and night, potentially modifying species' behavior. We assessed whether exposure to ALAN influences decision-making (directional swimming) in an intertidal rockfish (Girella laevisifrons) from the Southeastern Pacific. Using a Y-maze, we examined if exposure to ALAN or natural day/night conditions for one week affected the number of visits and time spent in three Y-maze compartments: dark and lit arms ("safe" and "risky" conditions, respectively) and a neutral "non-decision" area. The results showed that fish maintained in natural day/night conditions visited and spent more time in the dark arm, regardless of size. Instead, fish exposed to ALAN visited and spent more time in the non-decision area and their response was size-dependent. Hence, prior ALAN exposure seemed to disorient or reduce the ability of rock fish to choose dark conditions, deemed the safest for small fish facing predators or other potential threats.

Field experimental evidence of sandy beach community changes in response to artificial light at night (ALAN)

Artificial light at night (ALAN) is a pervasive but still under-recognized driver of global change. In coastal settings, a large majority of the studies assessing ALAN impacts has focused on individual species, even though it is unclear whether results gathered from single species can be used to predict community-wide responses. Similarly, these studies often treat species as single life-stage entities, ignoring the variation associated with distinct life stages. This study addresses both limitations by focusing on the effects of ALAN on a sandy beach community consisting of species with distinct early- and late-life stages. Our hypothesis was that ALAN alters community structure and these changes are mediated by individual species and also by their ontogenetic stages. A field experiment was conducted in a sandy beach of north-central Chile using an artificial LED system. Samples were collected at different night hours (8-levels in total) across the intertidal (9-levels) over several days in November and January (austral spring and summer seasons). The abundance of adults of all species was significantly lower in ALAN treatments. Early stages of isopods showed the same pattern, but the opposite was observed for the early stages of the other two species. Clear differences were detected in the zonation of these species during natural darkness versus those exposed to ALAN, with some adult-juvenile differences in this response. These results support our hypothesis and document a series of changes affecting differentially both early and late life stages of these species, and ultimately, the structure of the entire community. Although the effects described correspond to short-term responses, more persistent effects are likely to occur if ALAN sources become established as permanent features in sandy beaches. The worldwide growth of ALAN suggests that the scope of its effect will continue to grow and represents a concern for sandy beach systems.

The role of light pollution in mammalian metabolic homeostasis and its potential interventions: A critical review

Irregular or unnatural artificial light causes severe environmental stress on the survival and health of organisms, which is rapidly becoming a widespread new type of environmental pollution. A series of disruptive behaviors to body homeostasis brought about by light pollution, including metabolic abnormalities, are likely to be the result of circadian rhythm disturbances. Recently, the proposed role of light pollution in metabolic dysregulation has accelerated it into an emerging field. Hence, the regulatory role of light pollution in mammalian metabolic homeostasis is reviewed in this contribution. Light at night is the most widely affected type of light pollution, which disrupts metabolic homeostasis largely due to its disruption of daily food intake patterns, alterations of hormone levels such as melatonin and glucocorticoids, and changes in the rhythm of inflammatory factor production. Besides, light pollution impairs mammalian metabolic processes in an intensity-, photoperiod-, and wavelength-dependent manner, and is also affected by species, gender, and diets. Nevertheless, metabolic disorders triggered by light pollution are not irreversible to some extent. Potential interventions such as melatonin supplementation, recovery to the LD cycle, time-restricted feeding, voluntary exercise, wearing blue light-shied goggles, and bright morning light therapy open a bright avenue to prevent light pollution. This work will help strengthen the relationship between light information and metabolic homeostasis and provide new insights for the better prevention of metabolic disorders and light pollution.

Impacts of artificial light at night in marine ecosystems-A review

The globally widespread adoption of Artificial Light at Night (ALAN) began in the mid-20th century. Yet, it is only in the last decade that a renewed research focus has emerged into its impacts on ecological and biological processes in the marine environment that are guided by natural intensities, moon phase, natural light and dark cycles and daily light spectra alterations. The field has diversified rapidly from one restricted to impacts on a handful of vertebrates, to one in which impacts have been quantified across a broad array of marine and coastal habitats and species. Here, we review the current understanding of ALAN impacts in diverse marine ecosystems. The review presents the current state of knowledge across key marine and coastal ecosystems (sandy and rocky shores, coral reefs and pelagic) and taxa (birds and sea turtles), introducing how ALAN can mask seabird and sea turtle navigation, cause changes in animals predation patterns and failure of coral spawning synchronization, as well as inhibition of zooplankton Diel Vertical Migration. Mitigation measures are recommended, however, while strategies for mitigation were easily identified, barriers to implementation are poorly understood. Finally, we point out knowledge gaps that if addressed would aid in the prediction and mitigation of ALAN impacts in the marine realm.

Casting a light on the shoreline: The influence of light pollution on intertidal settings

Light pollution is becoming prevalent among other coastal stressors, particularly along intertidal habitats, arguably the most exposed to anthropogenic light sources. As the number of light pollution studies on sandy beaches, rocky shores and other intertidal habitats raises, commonalities, research gaps and venues can be identified. Hence, the influence of light pollution on the behavior and ecology of a variety of intertidal macro-invertebrates and vertebrates are outlined by examining 54 published studies. To date, a large majority of the reported effects of light pollution are negative, as expected from the analysis of many species with circadian rhythms or nocturnal habits, although the severity of those effects ranges widely. Experimental approaches are well represented throughout but methodological limitations in measurement units and standardization continue to limit the proposal of general conclusions across species and habitats. In addition, studies targeting community variables and the explicit influence of skyglow are heavily underrepresented. Likewise, studies addressing the interaction between light pollution and other natural and anthropogenic stressors are critically needed and represent a key venue of research. The nature of those interactions (synergistic, additive, antagonistic) will likely dictate the impact and management of light pollution in the decades ahead.

Artificial light at night and risk of mental disorders: A systematic review

BACKGROUND

Emerging evidence suggests a possible association between artificial light at night (LAN) exposure and physiological and behavioral changes, with implications on mood and mental health. Due to the increased amount of individuals' LAN exposure, concerns have been raised regarding harmful impact of light pollution on mental health at the population level.

AIM

To perform a systematic review of observational studies to investigate if light at night, assessed both indoor and outdoor, may be associated with an increased risk of mental diseases in humans.

METHODS

We reviewed the epidemiological evidence on the association between LAN exposure, assessed either via satellite photometry or via measurements of bedroom brightness, and mental disorders. We systematically searched the PubMed, Embase and Web of Science databases up to April 1, 2022. Studies were included if they assessed the link between indoor or outdoor artificial light at night and one or more mental disorders in human populations.

RESULTS

Nine eligible studies were included in this review: six studies had a cross-sectional design, two had a longitudinal design with a median follow-up of 24 months, and one was a case-cohort study. Overall, we found moderate evidence of a positive association between LAN exposure and depressive symptoms and to a lesser extent other mental disorders, though the number of studies was limited and potential residual confounding such as socioeconomic factors, noise, or air pollution may have influenced the results.

CONCLUSIONS

Although more robust evidence is needed, the epidemiological evidence produced so far seems to support an association between LAN and risk of depressive disorders.

A new apparatus to analyze meal-related ingestive behaviors in rats fed a complex multi-food diet

The measurement of the size and timing of meals provides critical insight into the processes underlying food intake. While most work has been conducted with a single food or fluid, the availability of food choices can also influence eating and interact with these processes. The 5-Item Food Choice Monitor (FCM), a device that continuously measures eating and drinking behaviors of rats provided up to 5 foods and 2 fluids simultaneously, was designed to allow study of food choices simultaneously with meal patterns. To validate this device, adult male and female (n = 8 each) Sprague-Dawley rats were housed in the FCM. Food and fluid intake were measured continuously (22-h/day) while rats were presented water and powdered chow. Then a cafeteria diet of 5 foods varying in macronutrient content, texture, and flavors were offered along with water. Lastly, the 5 foods were offered along with 0.3 M sucrose and water. Analyses were conducted to find optimal criteria for parceling ingestive behavior into meals, and then meal patterns were quantified. Total intake, as assessed by FCM software, was in good concordance with that measured by an independent scale. A minimum meal size of 1 kcal and a meal termination criterion of 15-min accounted for >90% of total intake and produced meal dynamics that were in register with the literature. Use of the cafeteria diet allowed comparisons between meal patterns with a single food versus a multi-food diet, as well as analyses of macronutrient-related food choices across subsets of meals. The FCM proved to accurately measure food intake over a 22-h period and was able to detect differences and similarities in the meal patterns of rats as a function of sex and food choice availability. Combined with any number of experimental manipulations, the FCM holds great promise in the investigation of the physiological and neural controls of ingestive behavior in a dietary environment that allows food choices, more closely emulating human eating conditions.

Even low light pollution levels affect the spatial distribution and timing of activity of a "light tolerant" bat species

By disrupting nocturnal landscapes worldwide, light pollution caused by Artificial Light At Night (ALAN) is recognized as a major threat to biodiversity. As even low light intensities might affect some taxa, concerns are arising about biological responses to widespread low light levels. We used data from a French citizen science bat monitoring program (1894 full-nights monitored on 1055 sites) to explore the landscape-scale effects of light on an open-space-foraging bat species, the Serotine bat (Eptesicus serotinus). We assessed this species' abundance and timing of night-time activity (median time of activity) at foraging sites. ALAN, and to a lesser extent moonlight, reduced E. serotinus abundance. ALAN delayed activity, and this delay was amplified during overcast nights. On the contrary, where there was no ALAN, the higher the cloud cover, the earlier the activity occurred. Cloud cover likely darkened the night sky in rural locations, whereas it amplified skyglow in light-polluted places, increasing ALAN effects on bats. Interestingly, moonlight also delayed activity but this effect was weakened where there was ALAN. Our study shows that even fine variations of light levels could affect the spatiotemporal distribution of a common species usually considered to be "light tolerant", with potential cascading effects on individual fitness and population dynamics. It stresses how urgent it is to preserve and restore dark areas to protect biodiversity from light pollution while working on light intensity and directivity where ALAN is needed.

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

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.

Minimizing Ecological Impacts of Marine Energy Lighting

Marine energy is poised to become an important renewable energy contributor for the U.S., but widespread deployment of the technology hinges on its benefits outweighing the potential ecological impacts. One stressor marine energy installations introduce is light, which is known to cause varying responses among wildlife and has not yet been addressed as an environmental concern. This review discusses requirements and regulations for similar structures and how lighting design choices can be made to meet these requirements while minimizing environmental consequences. More practical guidance on implementing lighting for marine energy is needed, as well as updated guidelines to reflect technological and research advances. Known responses of wildlife to light are introduced in addition to how the responses of individuals may lead to ecosystem-level changes. The impact of light associated with marine energy installations can be reduced by following basic guidance provided herein, such as removing excess lighting, using lights with high directionality, and employing controls to reduce light levels. Continued research on animal responses to light, such as findings on minimum light levels for animal responses, alongside the development of highly-sensitivity spectral characterization capabilities can further inform lighting guidelines for deploying future open ocean marine energy devices.

Artificial Light at Night (ALAN) negatively affects the settlement success of two prominent intertidal barnacles in the southeast Pacific

Many coastal processes are regulated by day/night cycles and are expected to be altered by Artificial Light at Night (ALAN). The goal of this study was to assess the influence of ALAN on the settlement rates of intertidal barnacles. A newly designed settlement plate equipped with a small central LED light source was used to quantify settlement rates in presence/absence of ALAN conditions. "ALAN plates" as well as regular settlement plates were deployed in the mid rocky intertidal zone. Both ALAN and control plates collected early and late settlers of the barnacles Notochthamalus scabrosus and Jehlius cirratus. Early settlers (pre-metamorphosis cyprids) were not affected by ALAN. By contrast, the density of late settlers (post-metamorphosis spats) was significantly lower in ALAN than in control plates for both species, suggesting detrimental ALAN impacts on the settlement process. The new ALAN plates represent an attractive and alternative methodology to study ALAN effects.