Natural Light Cycles Research Articles

Effects of rearing temperature on yolksac volume and growth rate in Lake Sturgeon, A. fulvescens, from hatch to age-1

In fishes, differences in egg incubation and water temperature in early rearing environments can have a significant impact on phenotypic development. This is particularly relevant during the first year of life when growth rate peaks and influences an individual's life history trajectory. In the present study, we examined the effect of differences in egg incubation, water temperature and overwintering on growth in Lake Sturgeon, A. fulvescens, throughout the first year of life. Developing embryos were incubated at 12–14 °C supplied with flow-through water and ambient light conditions in MacDonald hatching jars or allowed to adhere to substrate. Upon hatch (~9 days post-fertilization, dpf) larvae from each incubation treatment were then transferred to 16, 18 or 20 °C water increasing at a rate of 0.5 °C.day−1 and held at those temperatures until approximately 24 days post-hatch (dph). Experimental treatments were then transferred to a common garden set-up where duplicate treatment tanks were fed flow through river water at ambient temperature with natural light cycles. These were compared to fish transferred from a standard hatchery rearing treatment to the common garden tanks at the same time. Experimental fish were fed ad libitum twice daily throughout the growing season, but food was withheld when water temperature reached 1.5 °C (~6 months post-hatch, mph). Food was re-introduced at the start of spring the following year when water temperature exceeded 2 °C for three days in a row, (~ 10.5 mph). In experimental treatments, growth rate was highest in the 20 °C group during the first 3 months but converged with all other experimental treatments during winter before once again exceeding the other treatments following recovery from overwintering. Our data suggest that a temperature dependent growth phenotype was fixed during the first month of life in Lake Sturgeon that could have significant implications on hatchery rearing of this endangered species for conservation purposes.

Measuring Social Jetlag in Twitter Data

Social constraints have replaced the natural cycle of light and darkness as the main determinant of wake-up and activity times for many people. In this paper we show how Twitter activity can be used as a source of large-scale, naturally occurring data for the study of circadian rhythm in humans. Our year-long initial study is based on almost 1.5 million observations by over 200,000 users. The progression of the onset of Twitter activity times on free days in the course of the year is consistent with previous survey-based research on wake times. We show that the difference in wake-up time (implicating lack of sleep) on weekdays compared to Sundays is between 1 hour and over 2 hours depending on the time of year. The data also supports the assertion that Daylight Saving Time greatly disrupts the easing of social jetlag in the Spring transition.

Characterizing the modern light environment and its influence on circadian rhythms.

Humans have largely supplanted natural light cycles with a variety of electric light sources and schedules misaligned with day-night cycles. Circadian disruption has been linked to a number of disease processes, but the extent of circadian disruption among the population is unknown. In this study, we measured light exposure and wrist temperature among residents of an urban area during each of the four seasons, as well as light illuminance in nearby outdoor locations. Daily light exposure was significantly lower for individuals, compared to outdoor light sensors, across all four seasons. There was also little seasonal variation in the realized photoperiod experienced by individuals, with the only significant difference occurring between winter and summer. We tested the hypothesis that differential light exposure impacts circadian phase timing, detected via the wrist temperature rhythm. To determine the influence of light exposure on circadian rhythms, we modelled the impact of morning and night-time light exposure on the timing of the maximum wrist temperature. We found that morning and night-time light exposure had significant but opposing impacts on maximum wrist temperature timing. Our results demonstrate that, within the range of exposure seen in everyday life, night-time light can delay the onset of the maximum wrist temperature, while morning light can lead to earlier onset. Our results demonstrate that humans are minimizing natural seasonal differences in light exposure, and that circadian shifts and disruptions may be a more regular occurrence in the general population than is currently recognized.

The Endosymbiotic Coral Algae Symbiodiniaceae Are Sensitive to a Sensory Pollutant: Artificial Light at Night, ALAN.

Artificial Light at Night, ALAN, is a major emerging issue in biodiversity conservation, which can negatively impact both terrestrial and marine environments. Therefore, it should be taken into serious consideration in strategic planning for urban development. While the lion’s share of research has dealt with terrestrial organisms, only a handful of studies have focused on the marine milieu. To determine if ALAN impacts the coral reef symbiotic algae, that are fundamental for sustainable coral reefs, we conducted a short experiment over a period of one-month by illuminating isolated Symbiodiniaceae cell cultures from the genera Cladocopium (formerly Clade C) and Durusdinium (formerly Clade D) with LED light. Cell cultures were exposed nightly to ALAN levels of 0.15 μmol quanta m–2 s–1 (∼4–5 lux) with three light spectra: blue, yellow and white. Our findings showed that even in very low levels of light at night, the photo-physiology of the algae’s Electron Transport Rate (ETR), Non-Photochemical Quenching, (NPQ), total chlorophyll, and meiotic index presented significantly lower values under ALAN, primarily, but not exclusively, in Cladocopium cell cultures. The findings also showed that diverse Symbiodiniaceae types have different photo-physiology and photosynthesis performances under ALAN. We believe that our results sound an alarm for the probable detrimental effects of an increasing sensory pollutant, ALAN, on the eco-physiology of symbiotic corals. The results of this study point to the potential effects of ALAN on other organisms in marine ecosystem such as fish, zooplankton, and phytoplankton in which their biorhythms is entrained by natural light and dark cycles.

Estimating the loss and fragmentation of dark environments in mammal ranges from light pollution

A hallmark of the Anthropocene is the global expansion of pollution stemming from electric lighting. This evolutionarily novel phenomenon has left few spaces on Earth where natural light cycles remain unaltered. Assessing the exposure of species to light pollution is critical for developing conservation plans that address this expanding sensory pollutant. Here we used data from NASA's Visible Infrared Imaging Radiometer Suite to determine the contribution of full moonlight radiance to establish an ecologically-informed threshold of natural radiance. Using the geographic ranges of 351 mammals across the contiguous United States, we estimated the percentage of each species' range in which light pollution exceeded thresholds associated with direct emissions and skyglow, where it did not (“dark environment”), and the associated fragmentation of dark environments. Average mammal range contained 2.6% (95% CI: 2.3–3.2%) of area that consistently exceeded full moon radiance at point-source emissions, but with a large range among species (0–47.4%). Skyglow affected far greater percentages of ranges (X¯=24.3%; 95% CI: 22.1–26.8%). Nocturnal species had slightly greater exposure than diurnal species. Several families with the most impacted ranges included species of conservation concern (e.g., Molossidae; free-tailed bats). When assessing connectivity of dark environments, we found light pollution fragmented most mammal ranges and resulted in isolated dark refugia (e.g., 154% average increase in patches of dark environments). Identifying species with the greatest exposure to and dark environment fragmentation from light pollution is an important step for targeted conservation efforts of remaining dark refugia for light-sensitive species.

Artificial Light at Night Alters the Physiology and Behavior of Western Mosquitofish (Gambusia affinis)

Human population growth and its associated effects on the environment contribute to the rapid decrease of biodiversity worldwide. Artificial light at night (ALAN) is an anthropogenic pollutant that is increasing with the spread of urbanization and may contribute to biodiversity declines. ALAN alters the migration patterns of birds, communication in frogs, and impacts reproduction, behavior, and physiology of multiple other taxa. However, most of the studies on ALAN are based on terrestrial systems, and overall, the effects of ALAN on freshwater organisms are poorly understood. We investigated how ALAN affects the physiology, behavior, and reproduction of a widespread, tolerant species of freshwater fish.Gambusia affinisare small livebearing fish often found in urban streams. We exposed groups of femaleG. affinisto either a natural light cycle or a constant 24-h light cycle (ALAN) in the laboratory for 60 days. In another experiment, we exposed femaleG. affinisto the same treatments in outdoor mesocosms for 32 days. We found that exposure to ALAN lowered glucose levels in the brain and decreased swimming activity, but had no effect on cortisol release rates, reproduction, survival, or growth. This research is strengthened by measuring multiple metrics in response to ALAN and by incorporating both a field and laboratory component which confirm similar results. These results suggest that this tolerant species of fish may behaviorally adjust to ALAN rather than modulate their endocrine stress response.

Artificial Light at Night Advances Spring Phenology in the United States

Plant phenology is closely related to light availability as diurnal and seasonal cycles are essential environmental cues for organizing bio-ecological processes. The natural cycles of light, however, have been dramatically disrupted by artificial light at night (ALAN) due to recent urbanization. The influence on plant phenology of ALAN and its spatial variation remain largely unknown. By analyzing satellite data on ALAN intensity across the United States, here, we showed that ALAN tended to advance the start date of the growing season (SOS), although the overall response of SOS to ALAN was relatively weak compared with other potential factors (e.g., preseason temperature). The phenological impact of ALAN showed a spatially divergent pattern, whereby ALAN mainly advanced SOS at climatically moderate regions within the United States (e.g., Virginia), while its effect was insignificant or even reversed at very cold (e.g., Minnesota) and hot regions (e.g., Florida). Such a divergent pattern was mainly attributable to its high sensitivity to chilling insufficiency, where the advancing effect on SOS was only triggered on the premise that chilling days exceeded a certain threshold. Other mechanisms may also play a part, such as the interplay among chilling, forcing and photoperiod and the difference in species life strategies. Besides, urban areas and natural ecosystems were found to suffer from similar magnitudes of influence from ALAN, albeit with a much higher baseline ALAN intensity in urban areas. Our findings shed new light on the phenological impact of ALAN and its relation to space and other environmental cues, which is beneficial to a better understanding and projection of phenology changes under a warming and urbanizing future.

Applications of Raman spectroscopy in art and archaeology

Applications of Raman spectroscopy in art and archaeology

Application of chemometric methods for the determination of fading and age determination of blue ballpoint inks

AbstractThis study presents preliminary results for applicability of micro‐Raman and VIS–NIR reflectance spectroscopy in age determination of blue ballpoints inks containing phthalocyanine and crystal violet. Based on chemometric methods, 74 different random blue pens were classified to various types of inks. Then handwritten samples stored in different light conditions were subjected to the analysis. The first set of samples was stored for 7 years at room temperature in an envelope without direct exposure to the light, whereas the second set of samples was aged by exposing them to natural light cycle for 85 days. The L, a, b values were determined on the basis of recorded Raman and VIS–NIR spectra and then used for chemometric calculation. Based on those values, partial least squares models were built, allowing to obtain correlations between ∆E and Raman and reflectance spectra. Relative standard errors of prediction RSEP(%) for obtained models were calculated in the range 1.97–5.13 and 1.20–2.27 for Raman and VIS–NIR spectra, respectively. The proposed nondestructive method allows to estimate the age of daylight exposed samples.

Divergent expression of hypoxia response systems under deoxygenation in reef-forming corals aligns with bleaching susceptibility.

Exposure of marine life to low oxygen is accelerating worldwide via climate change and localized pollution. Mass coral bleaching and mortality have recently occurred where reefs have experienced chronic low oxygen events. However, the mechanistic basis of tolerance to oxygen levels inadequate to sustain normal functioning (i.e. hypoxia) and whether it contributes to bleaching susceptibility, remain unknown. We therefore experimentally exposed colonies of the environmentally resilient Acropora tenuis, a common reef-building coral from the Great Barrier Reef, to deoxygenation-reoxygenation stress that was aligned to their natural night-day light cycle. Specifically, the treatment involved removing the 'night-time O2 buffer' to challenge the inherent hypoxia thresholds. RNA-Seq analysis revealed that coral possess a complete and active hypoxia-inducible factor (HIF)-mediated hypoxia response system (HRS) homologous to other metazoans. As expected, A. tenuis exhibited bleaching resistance and showed a strong inducibility of HIF target genes in response to deoxygenation stress. We applied this same approach in parallel to a colony of Acropora selago, known to be environmnetally susceptible, which conversely exhibited a bleaching phenotype response. This phenotypic divergence of A. selago was accompanied by contrasting gene expression profiles indicative of varied effectiveness of their HIF-HRS. Based on our RNA-Seq analysis, we propose (a) that the HIF-HRS is central for corals to manage deoxygenation stress and (b) that key genes of this system (and the wider gene network) may contribute to variation in coral bleaching susceptibility. Our analysis suggests that heat shock protein (hsp) 70 and 90 are important for low oxygen stress tolerance and further highlights how hsp90 expression might also affect the inducibility of coral HIF-HRS in overcoming a metabolic crisis under deoxygenation stress. We propose that differences in coral HIF-HRS could be central in regulating sensitivity to other climate change stressors-notably thermal stress-that commonly drive bleaching.

Coral Gametogenesis Collapse under Artificial Light Pollution

Artificial light at night (ALAN) can have negative impacts on the health of humans and ecosystems.1-4 Marine organisms, including coral reefs in particular, rely on the natural light cycles of sunlight and moonlight to regulate various physiological, biological, and behavioral processes.5-8 Here, we demonstrate that light pollution caused delayed gametogenesis and unsynchronized gamete release in two coral species, Acropora millepora and Acropora digitifera, from the Indo-Pacific Ocean. Given the urbanization along major coasts, light pollution could thus further threaten coral communities' populations, which are already under severe degradation. A worldwide-modeled light pollution impact assessment is provided, which can help incorporate an important variable in coral reef conservation planning.

A meta-analysis of biological impacts of artificial light at night.

Natural light cycles are being eroded over large areas of the globe by the direct emissions and sky brightening that result from sources of artificial night-time light. This is predicted to affect wild organisms, particularly because of the central role that light regimes play in determining the timing of biological activity. Although many empirical studies have reported such effects, these have focused on particular species or local communities and have thus been unable to provide a general evaluation of the overall frequency and strength of these impacts. Using a new database of published studies, we show that exposure to artificial light at night induces strong responses for physiological measures, daily activity patterns and life history traits. We found particularly strong responses with regards to hormone levels, the onset of daily activity in diurnal species and life history traits, such as the number of offspring, predation, cognition and seafinding (in turtles). So far, few studies have focused on the impact of artificial light at night on ecosystem functions. The breadth and often strength of biological impacts we reveal highlight the need for outdoor artificial night-time lighting to be limited to the places and forms-such as timing, intensity and spectrum-where it is genuinely required by the people using it to minimize ecological impacts.

Zingiber officinale Ethanolic Extract Attenuated Reserpine-Induced Depression-Like Condition and Associated Hippocampal Aberrations in Experimental Wistar Rats.

BackgroundRepeated and regimented treatment with reserpine causes depression-like condition characterized by persistent mood disorder, feelings of severe despondency and dejection, thus altering the hippocampal morphology. Our study compared a well-known antidepressant (fluoxetine), with the potential of Zingiber officinale to ameliorate reserpine-induced depression and the associated hippocampal cornu ammonis 1 (CA1) neuronal cell damage.MethodsForty-eight male Wistar rats, weighing 130–160 g, were randomly assigned to 6 groups (n=8), housed in plastic cages under natural light and dark cycles at room temperature with access to feed and water ad libitum. Group-A (control) received distilled water. Group-B and Group-C orally received 400 mg/kg of Zingiber officinale and 10 mg/kg of fluoxetine, respectively, for 7 days, while Group-D intraperitoneally received 0.2 mg/kg of reserpine for 14 days. Group-E and Group-F intraperitoneally received 0.2 mg/kg of reserpine for 14 days followed by 400 mg/kg of Zingiber officinale and 10 mg/kg of fluoxetine respectively for 7 days. All animals were sacrificed by cervical dislocation at the end of experiment, and the brains hippocampi were dissected, excised and processed for various analyses including histology [H&E], histochemistry of GFAP expression by astrocytes and specific gene expressions including p53 gene, glutathione reductase (GSR), glutathione peroxidase and catalase (CAT).ResultsReserpine significantly depleted the expression of P53 and glutathione reductase (GSR) genes while significantly increasing the expression of glutathione peroxidase 1 (GPx-1) gene (P≤0.05). Also, a marked increase in the expression of catalase (CAT) gene was observed. Furthermore, histoarchitecture (photomicrographs) of hippocampus CA1 region showed disruption in the arrangement of pyramidal neurons and alterations in their morphologies when animals were treated with reserpine (Group D). There was also accompanying increased astrocyte densities within the CA1 region following reserpine treatment. These features indicated deleterious effects of reserpine. Both Zingiber officinale and fluoxetine treatments ameliorated these effects.ConclusionThese findings showed structural and molecular alterations associated with reserpine-induced depression. Also, Zingiber officinale was effective to provide ameliorative and protective effects against the neurotoxic effects of reserpine in the hippocampus, making it a potential candidate for treating depression and its associated neurodegenerative diseases.

Evaluation of the Impact of Behavioral Opportunities on Four Zoo-Housed Aardvarks (Orycteropus afer).

Simple SummaryEvaluations of enrichment are critical to determine whether or not the goals of an enrichment program are being achieved. However, evaluations can be challenging if a species’ active period occurs outside of their caretakers’ normal schedule. Aardvarks are an understudied, nocturnal species, and our aim was to assess how they used their enrichment (nightly and throughout the study), if enrichment achieved the stated behavioral goals, and the subsequent effects of goal-achieving enrichment on the aardvarks’ welfare. Four aardvarks were given seven different enrichment items based on two behavioral goals, foraging and exploring, and were observed three times during the night. The aardvarks’ enrichment use was impacted based on the goal of the enrichment, with aardvarks using the enrichment aimed at promoting foraging behavior more when enrichment was first given compared to enrichment that promoted exploring. However, exploring enrichment was used more later in the night. The enrichment did appear to achieve the stated behavioral goals, and the aardvarks continued using the enrichment throughout the entire eight-week study. In addition, there were increased affiliative and decreased agonistic interactions with more enrichment use, linking the achievement of these goals to positive indicators of welfare. The data presented contribute to the current knowledge on goal-based enrichment and its impact on animal welfare.Evaluations of enrichment are critical to determine if an enrichment program is meeting stated goals. However, nocturnal species can present a challenge if their active periods do not align with caretakers’ schedules. To evaluate enrichment for four aardvarks housed with a natural light cycle, we provided seven different enrichment items aimed at fulfilling two behavioral goals: exploring and foraging. We wanted to understand how the aardvarks used enrichment, if enrichment promoted the defined goals, and how enrichment that achieves its goals affects welfare indicators, including rates of pacing and social behaviors, behavioral diversity, and fecal glucocorticoid metabolites. Twenty-minute observations from video were performed three times a night for a total of 224 observed hours. We found significant differences in how the aardvarks used items from the two enrichment goals throughout the night, with foraging enrichment used more than exploring at first and exploring enrichment used more later. We found that items promoted their defined goals, and aardvarks showed no evidence of habituation throughout the eight-week study. The impact on selected welfare indicators provided evidence of potentially positive changes, including increased affiliative and decreased agonistic interactions accompanying increases in goal behaviors. These results contribute to the current knowledge available on the impact of goal-directed behavioral opportunities on zoo animal welfare.

Intensity of giraffe locomotor activity is shaped by solar and lunar zeitgebers

Natural cycles of light and darkness shift the balance of risks and gains for animals across space and time. Entrainment to photic cycles allows animals to spatiotemporally adapt their behavioural and physiological processes in line with interplaying ecological factors, such as temperature, foraging efficiency and predation risk. Until recently, our understanding of these chronobiological processes was limited by the difficulties of 24 h observations. Technological advances in GPS biotelemetry however are now allowing us unprecedented access to long-term, fine-scale activity data. Here we use data derived from frontline technology to present the first large-scale investigation into the effects of natural fluctuations of light and darkness on the locomotor activity patterns of a threatened African mega-herbivore, the giraffe (Giraffa spp.). Using data from a remote population of Angolan giraffe (G. g. angolensis) in the northern Namib Desert, Namibia, we reveal the first full picture of giraffe chronobiology in a landscape of fear. Furthermore, we present clear evidence of the effect of moonlight on the nocturnal activity patterns of large ungulates. Our results are in line with recent research demonstrating that, rather than a fixed internal representation of time (circadian clock), many surface-dwelling ungulates have plastic activity patterns that are vulnerable to modification by external factors including light and temperature. Relatedly, we highlight important conservation management implications of rising temperatures and increasing light pollution on the chronobiology of surface-dwelling mammals.

The role of natural light rhythm in the development of desynchronosis in the conditions of rotational shiftwork in the Arctic

Purpose. To study the effects of a natural light cycle on circadian rhythms of blood pressure (BP) and heart rate conditions of rotational shiftwork in the Far North. Material and Methods . Data of 24-h BP monitoring were analyzed in 373 male patients with hypertension stage II monthly round-trip sojourns to the Arctic compared with a similar group of 144 patients living in moderate climate (Tyumen, 57 N). The standard and chronobiological parameters of 24-h BP monitoring were analyzed in 93 randomly selected patients of the Far North group and 64 patients of the Tyumen group. The 24-h BP profile, circadian indices of systolic and diastolic BP, percentage contribution value, rhythm amplitude, acrophase, and diurnal mean value of 24-h BP rhythm were studied during the seasons of the year. Results. The circadian rhythms of HR and BP in hypertensive patients in the conditions of rotational shiftwork in the Arctic showed the signs of internal desynchronosis and significantly differed from those in Tyumen patients independently of a season. The lack of natural light in the Far North during the polar day and polar night resulted in the flattened curves of circadian BP and HR rhythms in the hypertensive patients. Other major differences consisted in the low-amplitude profile of the spectrum and the loss of 24-h component in this group. The seasonal changes in HR in the comparison group were insignificant unlike those in the Far North group, which showed maximum flattening of HR rhythm during the polar day and polar night. Winter season (polar night) was the most adverse for the main group of patients in regard to their 24-h BP profile, which was characterized by the maximum degree of circadian rhythm flattening and the predominance of high-frequency oscillations in the spectrum. Conclusions. The development of circadian and seasonal desynchronosis of the HR and BP rhythms in hypertensive patients in the conditions of rotational shiftwork in the Arctic was caused not only by the labour characteristics and the climatic factors, but also by the natural light rhythmicity in the high latitude.

Artificial light at night alters the sexual behaviour and fertilisation success of the common toad

Artificial Light At Night (ALAN) is an emerging pollution, that dramatically keeps on increasing worldwide due to urbanisation and transport infrastructure development. In 2016, it nearly affected 23% of the Earth’s surface. To date, all terrestrial and aquatic ecosystems have been affected. The disruption of natural light cycles due to ALAN is particularly expected for nocturnal species, which require dark periods to forage, move, and reproduce. Apart from chiropterans, amphibians contain the largest proportion of nocturnal species among vertebrates exhibiting an unfavourable conservation status in most parts of the world and living in ALAN polluted areas. Despite the growing number of studies on this subject, our knowledge on the direct influence of nocturnal lighting on amphibians is still scarce. To better understand the consequences of ALAN on the breeding component of amphibian fitness, we experimentally exposed male breeding common toads (Bufo bufo) to ecologically relevant light intensities of 0.01 (control), 0.1 or 5 lux for 12 days. At mating, exposed males took longer than controls to form an amplexus, i.e. to pair with a female, and broke amplexus before egg laying, while controls never did. These behavioural changes were associated with fitness alteration. The fertilisation rate of 5 lux-exposed males was reduced by 25%. Salivary testosterone, which is usually correlated with reproductive behaviours, was not altered by ALAN. Our study demonstrates that ALAN can affect the breeding behaviour of anuran species and reduce one component of their fitness. Given the growing importance of ALAN, more work is needed to understand its long-term consequences on the behaviour and physiology of individuals. It appears essential to identify deleterious effects for animal populations and propose appropriate management solutions in an increasingly brighter world.

Dark Design: A New Framework for Advocacy and Creativity for the Nocturnal Commons

Urbanization continues to provide habitat for more and more of the planet’s human population. Accompanying this process are the energy, transport, and service infrastructures that support urban life. Enmeshed in these networks is artificial illumination and its unintended consequences. Light pollution, for instance, accounts for a growing global carbon footprint, yet more efficient artificial lighting methods using LEDs have resulted in increasingly higher levels of brightness at night. This is altering natural cycles of light and dark, directly impacting on the circadian rhythms of our bodies and having disastrous effects upon other species and their ecosystems. This issue of critical importance has been referred to by some scientists as a hidden global challenge but the public awareness and understanding of it is negligible. Where is design in addressing such poor performance? The growing problem of how we perceive darkness and the attempts to manage it, typically through artificial illumination, requires new design strategies to create viable alternatives to current pathways. How can we advocate for the “nocturnal commons” when the majority of society does not even know what is disappearing or understand the implications? This article proposes the concept of “Dark Design” to set out a new framework for advocacy and creativity to raise awareness of these complex issues and address them. By bringing together a diverse range of approaches, “Dark Design” seeks to establish a field for emerging principles and practices to design with darkness rather than against it. In doing so, it calls for the important and urgent need for design to commit, act and engage others in the future of our planet, its people, and non-human species.

Anthropogenic Light Disrupts Natural Light Cycles in Critical Conservation Areas

Anthropogenic lighting drastically alters nocturnal environments, threatening a wide range of species by disrupting light regimes that regulate fundamental biological processes such as reproduction, foraging, and predator defense. We translate satellite measures of anthropogenic light radiating from the earth to a biologically relevant measurement – the amount of light scattered back to the earth (horizontal illuminance). Anthropogenic light exceeding the natural level produced by stars, galactic light, and airglow on a clear moonless night (i.e., new moon conditions) affects 22.9% of the Earth’s terrestrial surface, as well as 51.0% of Key Biodiversity Area units, 77.1% of Global Protected Area units, and approximately 20% of the most biodiverse areas for mammals, birds, and amphibians. Thus, due to anthropogenic sources, these environments experience at least double the levels of natural illuminance during half of the night hours in a year. To facilitate biological interpretation of these levels of anthropogenic illuminance observed globally, we undertook a systematic literature review of animal responses to changing nocturnal light levels. Known biological effects from the current anthropogenic illuminance levels range from behavioral and physiological alterations to increased mortality, which have been documented in 117 species from 23 orders and 8 classes. These findings provide a biological perspective on global light pollution, and they identify regions where reductions in anthropogenic illuminance would yield the greatest benefits for conserving biodiversity.

Sustainability of coral reefs are affected by ecological light pollution in the Gulf of Aqaba/Eilat

As human populations grow and lighting technologies improve, artificial light gradually alters natural cycles of light and dark that have been consistent over long periods of geological and evolutionary time. While considerable ecological implications of artificial light have been identified in both terrestrial and aquatic habitats, knowledge about the physiological and molecular effects of light pollution is vague. To determine if ecological light pollution (ELP) impacts coral biological processes, we characterized the transcriptome of the coral Acropora eurystoma under two different light regimes: control conditions and treatment with light at night. Here we show that corals exposed to ELP have approximately 25 times more differentially expressed genes that regulate cell cycle, cell proliferation, cell growth, protein synthesis and display changes in photo physiology. The finding of this work confirms that ELP acts as a chronic disturbance that may impact the future of coral reefs.