polar night
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2022 ◽  
Vol 7 (4) ◽  
pp. 84-89
Author(s):  
A. N. Zhekalov ◽  
I. Yu. Mishin

Introduction. The climatogeographic conditions of the Arctic Zone of the Russian Federation are determined by the proximity to the North Pole of the Earth and are characterized by a number of certain cyclical changes that do not take place in the middle latitudes — the polar day and the polar night. The high-latitude location determines the long period of the polar night, lasting from 98 to 133 days. Being the hallmark of the Arctic, the polar night is an integral part of service in the Arctic region, it has an impact on every geographically involved person, without exception.Purpose of work. To assess the mechanisms of the pathogenesis of visual impairment that develop during the polar night in naval specialists.Materials and research methods. The study involved 92 people. The surveyed contingent is male contract servicemen of the Navy, aged from 21 to 45 years. The analysis of the morbidity structure according to the ophthalmological profile was carried out during the polar night from November 20, 2020 to January 20, 2021 using an epidemiological method of a case-control study. The assessment of unfavorable climatic and geographical factors of the Arctic region during the polar night was carried out by the method of analytical observation and data recording from November 20, 2020 to January 20, 2021 using the example of the Novaya Zemlya archipelago, Belushya Guba village. On the basis of an integral analysis of epidemiological indicators, climatogeographic and clinical and morphological observations, a pathophysiological assessment of diseases of the organ of vision, developing during the polar night in naval specialists, was carried out.Research results show a high level of ophthalmological morbidity during the polar night among naval specialists serving on the Novaya Zemlya archipelago.Conclusions. Climatogeographic factors of the Arctic region have a polyetiological effect on the formation of mechanisms of pathogenesis of disorders of visual functions that develop in naval specialists during the polar night.


2021 ◽  
Vol 8 ◽  
Author(s):  
Igor A. Dmitrenko ◽  
Vladislav Y. Petrusevich ◽  
Ksenia Kosobokova ◽  
Alexander S. Komarov ◽  
Caroline Bouchard ◽  
...  

The diel vertical migration (DVM) of zooplankton is one of the largest species migrations to occur globally and is a key driver of regional ecosystems and the marine carbon pump. The dramatic changes in the Arctic environment in recent years, mainly associated with sea-ice decline, may have wide significance for the Arctic shelf ecosystems including DVM. Observations have revealed the occurrence of DVM in ice-covered Arctic waters, however, there have yet to be observations of DVM from the extensive Siberian shelves in the Eurasian Arctic and no analysis of how the sea-ice decline may affect DVM. Here, 2 yearlong time series of acoustic backscatter, collected by moored acoustic Doppler current profilers in the eastern Laptev Sea from August 1998 to August 1999, were used to examine the annual cycle of acoustic scattering, and therefore the annual cycle of DVM in the area. The acoustic time series were used along with atmospheric and oceanic reanalysis and satellite data. Our observations show that DVM did not occur during polar night and polar day, but is active during the spring and fall transition periods when there is a diurnal cycle in light conditions. DVM began beneath the fast ice at the end of polar night and increased in intensity through spring. However, the formation of a large polynya along the landfast ice edge in late March 1999 caused DVM to abruptly cease near the fast ice edge, while DVM persisted through spring to the start of polar day at the onshore mooring. We associate this cessation of synchronized DVM ∼1 month ahead of polar day with a predator-avoidance behavior of zooplankton in response to higher polar cod abundance near the polynya. During polar day, the intensity of acoustic scattering was attributed to the riverine suspended particles. Overall, our results highlight the occurrence of DVM on the Siberian shelves, the cessation of synchronized DVM when a polynya opens up nearby, and the potential impact of significant trends toward a more extensive Laptev Sea polynya as part of changing ice conditions in the Eurasian Arctic and their impact on the Arctic shelf ecology.


2021 ◽  
Author(s):  
Igor Shulman ◽  
Jonathan H. Cohen ◽  
Mark A. Moline ◽  
Stephanie Anderson ◽  
E. Joseph Metzger ◽  
...  

AbstractDuring polar nights in January 2012 and 2017, significantly higher bioluminescence (BL) potential emissions in the upper 50 m were observed in the fjord Rijpfjorden (Svalbard, Norway) in comparison to offshore stations (located on the shelf-break, shelf-slope areas and in the deeper water). The objective of this paper is to better understand why, during two polar nights (separated by 5 years), the values of BL potential in the northern Svalbard fjord are higher than at offshore stations, and what the role of advection is in observed elevated BL potential values in the top 50 m of the fjord. To address the above objective, we applied the same BL potential modeling approach and strategies during polar nights for both 2012 and 2017. For both years, advection of BL potential from offshore (including upwelling along the shelf, shelf-slope) produced an increase of BL potential in the fjord area, in spite of the introduction of mortality in bioluminescent organisms. Observations of BL potential indicated high emissions at depths below 100 m at offshore stations for both polar nights. Our modeling studies demonstrated that these high values of BL potential below 100 m are upwelled and advected to the top 50 m of the fjord. We demonstrated that upwelling and advection of these deep high BL potential values (and therefore, upwelling and advection of corresponding bioluminescent taxa) from offshore areas are dominant factors in observed BL potential dynamics in the top 50 m in the fjord.


2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Matthias Wietz ◽  
Christina Bienhold ◽  
Katja Metfies ◽  
Sinhué Torres-Valdés ◽  
Wilken-Jon von Appen ◽  
...  

AbstractThe Arctic Ocean features extreme seasonal differences in daylight, temperature, ice cover, and mixed layer depth. However, the diversity and ecology of microbes across these contrasting environmental conditions remain enigmatic. Here, using autonomous samplers and sensors deployed at two mooring sites, we portray an annual cycle of microbial diversity, nutrient concentrations and physical oceanography in the major hydrographic regimes of the Fram Strait. The ice-free West Spitsbergen Current displayed a marked separation into a productive summer (dominated by diatoms and carbohydrate-degrading bacteria) and regenerative winter state (dominated by heterotrophic Syndiniales, radiolarians, chemoautotrophic bacteria, and archaea). The autumn post-bloom with maximal nutrient depletion featured Coscinodiscophyceae, Rhodobacteraceae (e.g. Amylibacter) and the SAR116 clade. Winter replenishment of nitrate, silicate and phosphate, linked to vertical mixing and a unique microbiome that included Magnetospiraceae and Dadabacteriales, fueled the following phytoplankton bloom. The spring-summer succession of Phaeocystis, Grammonema and Thalassiosira coincided with ephemeral peaks of Aurantivirga, Formosa, Polaribacter and NS lineages, indicating metabolic relationships. In the East Greenland Current, deeper sampling depth, ice cover and polar water masses concurred with weaker seasonality and a stronger heterotrophic signature. The ice-related winter microbiome comprised Bacillaria, Naviculales, Polarella, Chrysophyceae and Flavobacterium ASVs. Low ice cover and advection of Atlantic Water coincided with diminished abundances of chemoautotrophic bacteria while others such as Phaeocystis increased, suggesting that Atlantification alters microbiome structure and eventually the biological carbon pump. These insights promote the understanding of microbial seasonality and polar night ecology in the Arctic Ocean, a region severely affected by climate change.


2021 ◽  
Author(s):  
Magdalena Wutkowska ◽  
Anna Vader ◽  
Ramiro Logares ◽  
Eric Pelletier ◽  
Tove M. Gabrielsen

At high latitudes, strong seasonal differences in light availability affect marine organisms and restrict the timing of ecosystem processes. Marine protists are key players in Arctic aquatic ecosystems, yet little is known about their ecological roles over yearly cycles. This is especially true for the dark polar night period, which up until recently was assumed to be devoid of biological activity. A 12 million transcripts catalogue was built from 0.45-10 μm protist assemblages sampled over 13 months in a time series station in an arctic fjord in Svalbard. Community gene expression was correlated with seasonality, with light as the main driving factor. Transcript diversity and evenness were higher during polar night compared to polar day. Light-dependent functions had higher relative expression during polar day, except phototransduction. 64% of the most expressed genes could not be functionally annotated, yet up to 78% were identified in arctic samples from Tara Oceans, suggesting that arctic marine assemblages are distinct from those from other oceans. Our study increases understanding of the links between extreme seasonality and biological processes in pico- and nanoplanktonic protists. Our results set the ground for future monitoring studies investigating the seasonal impact of climate change on the communities of microbial eukaryotes in the High Arctic.


2021 ◽  
Vol 8 ◽  
Author(s):  
Katarzyna Zamelczyk ◽  
Agneta Fransson ◽  
Melissa Chierici ◽  
Elizabeth Jones ◽  
Julie Meilland ◽  
...  

Planktic foraminfera and shelled pteropods are important calcifying groups of zooplankton in all oceans. Their calcium carbonate shells are sensitive to changes in ocean carbonate chemistry predisposing them as an important indicator of ocean acidification. Moreover, planktic foraminfera and shelled pteropods contribute significantly to food webs and vertical flux of calcium carbonate in polar pelagic ecosystems. Here we provide, for the first time, information on the under-ice planktic foraminifera and shelled pteropod abundance, species composition and vertical distribution along a transect (82°–76°N) covering the Nansen Basin and the northern Barents Sea during the polar night in December 2019. The two groups of calcifiers were examined in different environments in the context of water masses, sea ice cover, and ocean chemistry (nutrients and carbonate system). The average abundance of planktic foraminifera under the sea-ice was low with the highest average abundance (2 ind. m–3) close to the sea-ice margin. The maximum abundances of planktic foraminifera were concentrated at 20–50 m depth (4 and 7 ind. m–3) in the Nansen Basin and at 80–100 m depth (13 ind. m–3) close to the sea-ice margin. The highest average abundance (13 ind. m–3) and the maximum abundance of pteropods (40 ind. m–3) were found in the surface Polar Water at 0–20 m depth with very low temperatures (–1.9 to –1°C), low salinity (<34.4) and relatively low aragonite saturation of 1.43–1.68. The lowest aragonite saturation (<1.3) was observed in the bottom water in the northern Barents Sea. The species distribution of these calcifiers reflected the water mass distribution with subpolar species at locations and depths influenced by warm and saline Atlantic Water, and polar species in very cold and less saline Polar Water. The population of planktic foraminifera was represented by adults and juveniles of the polar species Neogloboquadrina pachyderma and the subpolar species Turborotalita quinqueloba. The dominating polar pteropod species Limacina helicina was represented by the juvenile and veliger stages. This winter study offers a unique contribution to our understanding of the inter-seasonal variability of planktic foraminfera and shelled pteropods abundance, distribution and population size structure in the Arctic Ocean.


PLoS Biology ◽  
2021 ◽  
Vol 19 (10) ◽  
pp. e3001413
Author(s):  
Jonathan H. Cohen ◽  
Kim S. Last ◽  
Corie L. Charpentier ◽  
Finlo Cottier ◽  
Malin Daase ◽  
...  

Light plays a fundamental role in the ecology of organisms in nearly all habitats on Earth and is central for processes such as vision and the entrainment of the circadian clock. The poles represent extreme light regimes with an annual light cycle including periods of Midnight Sun and Polar Night. The Arctic Ocean extends to the North Pole, and marine light extremes reach their maximum extent in this habitat. During the Polar Night, traditional definitions of day and night and seasonal photoperiod become irrelevant since there are only “twilight” periods defined by the sun’s elevation below the horizon at midday; we term this “midday twilight.” Here, we characterize light across a latitudinal gradient (76.5° N to 81° N) during Polar Night in January. Our light measurements demonstrate that the classical solar diel light cycle dominant at lower latitudes is modulated during Arctic Polar Night by lunar and auroral components. We therefore question whether this particular ambient light environment is relevant to behavioral and visual processes. We reveal from acoustic field observations that the zooplankton community is undergoing diel vertical migration (DVM) behavior. Furthermore, using electroretinogram (ERG) recording under constant darkness, we show that the main migratory species, Arctic krill (Thysanoessa inermis) show endogenous increases in visual sensitivity during the subjective night. This change in sensitivity is comparable to that under exogenous dim light acclimations, although differences in speed of vision suggest separate mechanisms. We conclude that the extremely weak midday twilight experienced by krill at high latitudes during the darkest parts of the year has physiological and ecological relevance.


2021 ◽  
Vol 22 (3) ◽  
pp. 42-46
Author(s):  
A. N. Zhekalov ◽  
◽  
I. U. Mishin ◽  

Aim. To carry out a pathophysiological substantiation of the specificity of diseases of the organ of vision, developing under the influence of a complex of climatic and geographical factors of the Arctic region. Materials and methods. Using a retrospective epidemiological method of case-control study on the basis of branch No. 8 of FGKU 1469 VMKG of the Ministry of Defense of Russia, an analysis of the morbidity structure by ophthalmological profile for a three-year period (2018-2020) among military personnel aged 18 to 45 years military service in the Novaya Zemlya archipelago, Belushya Guba village. The method of analytical observation and data recording was used to assess the complex of unfavorable climatic and geographical factors of the Arctic region on the example of the Novaya Zemlya archipelago, Belushya Guba village. On the basis of an integral assessment of epidemiological and climatogeographic observations, a pathophysiological substantiation of the specificity of nosological groups of diseases of the organ of vision, developing under the influence of a complex of unfavorable factors of the Arctic region, is given. Results. The study involved 237 people. During the study period, 540 requests for ophthalmological help were registered. Of these, 64.26% are pathologies of inflammatory genesis, 32.6% are refractive disorders, 3.14% are diseases, the pathogenesis of which is associated with metabolic disorders in the body. The pathophysiological substantiation of the revealed morbidity structure according to the ophthalmological profile is due to the influence of a complex of unfavorable climatic and geographical factors of the Arctic region. Under the influence of wind and low temperatures, the structure of the tear film changes, the secretion of the meibomian glands becomes more viscous, as a result of which its concentration in the tear fluid decreases, and the eyes lose their protective barrier. The congealed secret clogs the ducts of the meibomian glands, which leads to their inflammation – meibomyitis. In turn, the insufficiency of the tear film provokes a decrease, and in more severe cases, a complete loss of natural tear production and the development of dry eye syndrome. The development of acute and chronic conjunctivitis is facilitated by a decrease in the reactivity of the body due to hypovitaminosis against the background of exposure to irritating climatic factors. With inflammation of the mucous membrane of the eyelids, the frequency of inflammatory diseases of the lacrimal ducts and the lacrimal gland increases, which causes obstruction of the lacrimal tubules and hyperfunction of the lacrimal glands. On a polar night, the perception of bright lighting is aggravated, a long stay near which provokes the development of a spasm of accommodation and subsequently its habitual excessive stress. Lack of natural light during the polar night is a predisposing factor for the development of myopia. In addition, during the polar night, there is a high probability of developing A-vitamin deficiency, which results in impaired night vision, damage to the conjunctiva, and in more severe cases, the cornea. In the spring or early summer, when there is snow, and solar activity is high, the ultraviolet rays reflected from the snow enter the eyes, causing a retinal burn, ultraviolet ophthalmia develops. Conclusion. The impact of a complex of climatic and geographic factors of the Arctic region on the body provokes a restructuring of regulatory physiological processes and the launch of pathogenetic mechanisms leading to the emergence and development of inflammatory diseases of the eye and its accessory apparatus, refractive disorders, as well as pathology, which is based on metabolic disorders.


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