scholarly journals Upper thermal threshold of Lepidurus arcticus (Branchiopoda, Notostraca) in lakes on the southern outreach of its distribution range

2021 ◽  
Vol 41 ◽  
pp. 50-88
Author(s):  
Tore Qvenild ◽  
Eirik Fjeld ◽  
Arne Fjellheim ◽  
Johan Hammar ◽  
Trygve Hesthagen ◽  
...  
Keyword(s):  
Water Temperature ◽  
Fish Predation ◽  
High Arctic ◽  
Water Bodies ◽  
The Arctic ◽  
Thermal Threshold ◽  
Tadpole Shrimp ◽  
Area North ◽  
Regulated Lakes ◽  
Southern Island

The Arctic tadpole shrimp Lepidurus arcticus has a circumpolar distribution and the Scandes (Fennoscandian Mountains) marks its southernmost limit in Europe. Within this area, 391 natural and 88 regulated lakes with L. arcticus have been identified, of which 87% are above the treeline. The lakes hosting L. arcticus decrease in altitude from south to north, which results from its temperature preferences. The majority of the locations are at a lower lake air temperature than 11°C which is equivalent to a water temperature near 14°C. This is assumed to be near the upper thermal threshold for L. arcticus. In lakes that exceed this average summer water temperature (1 July – 15 September), sustainable populations seem to be rare. In warmer lakes, life cycle mismatches are assumed to explain the absence of L. arcticus, most likely by affecting the embryo and juvenile stages. The distribution appears to be dichotomous, with one large northern area north of 65°N and one separated southern “island”. Only two locations of L. arcticus are known for the area between latitudes 62.88 and 64.39°N. In this part of the Scandes, the lakes are likely too warm to host L. arcticus as most of them are situated below 700 m a.s.l. This may also be the case in the northernmost region, north of 70°N, where only 11 populations are recorded. Most of the lakes in this area typically occurs below 400 m a.s.l. L. arcticus populations are sensitive to fish predation, and dense fish populations may be another stressor limiting its distribution. In contrast to water bodies in the High Arctic where L. arcticus only exists in shallow, fishless ponds, in the Scandes they co-exist with fish in 97% of the findings. Global warming has already modified the environment of the Scandes, and populations of L. arcticus are at threat in many of the small and shallow water bodies at low altitudes.

scholarly journals Environmental conditions limit the distribution of Lepidurus arcticus (Branchiopoda, Notostraca) in lakes on the Hardangervidda mountain plateau, Southern Norway

2019 ◽  
Vol 39 ◽  
pp. 77-110 ◽  
Author(s):  
Tore Qvenild ◽  
Trygve Hesthagen
Keyword(s):  
Water Quality ◽  
Salmo Trutta ◽  
Growing Season ◽  
Fish Predation ◽  
Mean Value ◽  
The Arctic ◽  
Striking Difference ◽  
Brown Trout Salmo Trutta ◽  
Tadpole Shrimp ◽  
Southern Norway

The Arctic tadpole shrimp Lepidurus arcticus has a circumpolar distribution where the Hardangervidda mountain plateau in Norway marks its southernmost limit. Within this area, we searched for L. arcticus in 238 lakes in 27 catchments. On Hardangervidda, the distribution pattern of L. arcticus is highly skewed. In the 16 catchments located in the central and eastern parts, L. arcticus was recorded in 70% of all the lakes studied (n=191). The remaining 11 catchments located in western areas, are almost free of lakes with L. arcticus (n=47). The most striking difference between these two areas is the significantly higher level of snow deposition in the western areas. This delays the ice break-up, which results in lower water temperatures and a shorter growing season. The water of lakes in western areas (N=36) is also more dilute than those in the central and eastern areas (N=201), with mean calcium concentrations of 0.81±0.48 and 1.62±1.12 mg L-1, respectively. In the lakes in the central and eastern areas hosting L. arcticus (N=95), the mean value was slightly higher (1.67±1.14 mg L-1). The combination of low water temperature, a short growing season and dilute water low in calcium may explain the near total absence of L. arcticus in the western part of Hardangervidda. All lakes contain brown trout Salmo trutta, and as L. arcticus is heavily sought for as food, the analyses of fish stomachs are the most reliable method of detecting the species. However, this prey-predator relationship may severely reduce the population of L. arcticus, and their presence may also be a function of the proximity of species refugia. This is evident in the context of fish predation, but also of water quality. Hence, in the central and eastern parts of the plateau, where L. arcticus is common, their occurrence increased significantly with lake size, being found in 54% of the lakes <1.0 km2, as opposed to 97% in the bigger lakes. Furthermore, L. arcticus is most frequently found in lakes at altitudes between 1100 and 1299 m a.s.l. We conclude that environmental constraints limit the distribution of L. arcticus on Hardangervidda. The projected increase in temperature towards the end of this century may exterminate L. arcticus from the lower parts of Hardangervidda, especially in the most shallow lakes. Many of the lakes have water quality with pH <6.0 and calcium concentration <1.0 mg L-1. In such lakes L. arcticus is living on the edge of its survival, and the projected increase in precipitation may dilute the waters even further, pushing L. arcticus nearer to its extinction threshold.

Pelagic Amphipods of the Slope Waters of Northeast Greenland

1968 ◽  
Vol 25 (8) ◽  
pp. 1637-1650 ◽  
Author(s):  
John R. Tencati ◽  
Stephen R. Geiger
Keyword(s):  
Continental Shelf ◽  
High Arctic ◽  
The Arctic ◽  
Secondary Sexual Characteristics ◽  
Sexual Characteristics ◽  
Area North ◽  
Similar Area ◽  
Bottom Depth ◽  
Arctic Area ◽  
Arctic Fauna

Nine species of pelagic amphipods representing eight genera were collected from the drifting ice station Arlis II over the continental shelf and slope off northeast Greenland, from 77°29′N lat, 9°38′W long to 67°03′N lat, 26°18′W long. Parathemisto abyssorum predominated in this area and in a similar area of the Beaufort Sea, but was less abundant in a high arctic area north of Greenland.Gammarus wilkitzkii, Apherusa glacialis, Pseudalibrotus nanseni, and probably Eusirus holmii are associated with the underside of ice and their distribution is apparently independent of bottom depth. Gammarus wilkitzkii, A. glacialis, P. abyssorum, and P. libellula reproduce in the waters off northeast Greenland. The boreal species Cyphocaris bouvieri is newly recorded from northeast Greenland waters. An ellobiopsid parasite, Thalassomyces marsupii, hinders the development of some primary and secondary sexual characteristics of P. abyssorum.The zooplankton fauna off northeast Greenland is a continuation of the arctic fauna with a definite, but perhaps irregular, boreal influence and suggests that water under an ice cover may not always be arctic.

Summer phytoplankton of the northern Barents Sea (75–80º N)

2019 ◽  
pp. 8-19
Author(s):  
Larisa A. Pautova ◽  
Vladimir A. Silkin ◽  
Marina D. Kravchishina ◽  
Valeriy G. Yakubenko ◽  
Anna L. Chultsova
Keyword(s):  
Barents Sea ◽  
Weighted Average ◽  
Arctic Basin ◽  
High Arctic ◽  
Alexandrium Tamarense ◽  
Warm Water ◽  
The Arctic ◽  
Absolute Maximum ◽  
Deep Trench ◽  
Maximum Biomass

The structure of the summer planktonic communities of the Northern part of the Barents sea in the first half of August 2017 were studied. In the sea-ice melting area, the average phytoplankton biomass producing upper 50-meter layer of water reached values levels of eutrophic waters (up to 2.1 g/m3). Phytoplankton was presented by diatoms of the genera Thalassiosira and Eucampia. Maximum biomass recorded at depths of 22–52 m, the absolute maximum biomass community (5,0 g/m3) marked on the horizon of 45 m (station 5558), located at the outlet of the deep trench Franz Victoria near the West coast of the archipelago Franz Josef Land. In ice-free waters, phytoplankton abundance was low, and the weighted average biomass (8.0 mg/m3 – 123.1 mg/m3) corresponded to oligotrophic waters and lower mesotrophic waters. In the upper layers of the water population abundance was dominated by small flagellates and picoplankton from, biomass – Arctic dinoflagellates (Gymnodinium spp.) and cold Atlantic complexes (Gyrodinium lachryma, Alexandrium tamarense, Dinophysis norvegica). The proportion of Atlantic species in phytoplankton reached 75%. The representatives of warm-water Atlantic complex (Emiliania huxleyi, Rhizosolenia hebetata f. semispina, Ceratium horridum) were recorded up to 80º N, as indicators of the penetration of warm Atlantic waters into the Arctic basin. The presence of oceanic Atlantic species as warm-water and cold systems in the high Arctic indicates the strengthening of processes of “atlantificacion” in the region.

scholarly journals Characterization of Transport Regimes and the Polar Dome during Arctic Spring and Summer using in-situ Aircraft Measurements

2019 ◽  
Author(s):  
Heiko Bozem ◽  
Peter Hoor ◽  
Daniel Kunkel ◽  
Franziska Köllner ◽  
Johannes Schneider ◽  
...  
Keyword(s):  
Lower Troposphere ◽  
High Arctic ◽  
The Arctic ◽  
Trace Gas ◽  
Second Phase ◽  
Aerosol Formation ◽  
Transport Barrier ◽  
Data Set ◽  
Air Masses ◽  
Mixing Ratios

Abstract. The springtime composition of the Arctic lower troposphere is to a large extent controlled by transport of mid-latitude air masses into the Arctic, whereas during the summer precipitation and natural sources play the most important role. Within the Arctic region, there exists a transport barrier, known as the polar dome, which results from sloping isentropes. The polar dome, which varies in space and time, exhibits a strong influence on the transport of air masses from mid-latitudes, enhancing it during winter and inhibiting it during summer. Furthermore, a definition for the location of the polar dome boundary itself is quite sparse in the literature. We analyzed aircraft based trace gas measurements in the Arctic during two NETCARE airborne field camapigns (July 2014 and April 2015) with the Polar 6 aircraft of Alfred Wegener Institute Helmholtz Center for Polar and Marine Research (AWI), Bremerhaven, Germany, covering an area from Spitsbergen to Alaska (134° W to 17° W and 68° N to 83° N). For the spring (April 2015) and summer (July 2014) season we analyzed transport regimes of mid-latitude air masses travelling to the high Arctic based on CO and CO2 measurements as well as kinematic 10-day back trajectories. The dynamical isolation of the high Arctic lower troposphere caused by the transport barrier leads to gradients of chemical tracers reflecting different local chemical life times and sources and sinks. Particularly gradients of CO and CO2 allowed for a trace gas based definition of the polar dome boundary for the two measurement periods with pronounced seasonal differences. For both campaigns a transition zone rather than a sharp boundary was derived. For July 2014 the polar dome boundary was determined to be 73.5° N latitude and 299–303.5 K potential temperature, respectively. During April 2015 the polar dome boundary was on average located at 66–68.5° N and 283.5–287.5 K. Tracer-tracer scatter plots and probability density functions confirm different air mass properties inside and outside of the polar dome for the July 2014 and April 2015 data set. Using the tracer derived polar dome boundaries the analysis of aerosol data indicates secondary aerosol formation events in the clean summertime polar dome. Synoptic-scale weather systems frequently disturb this transport barrier and foster exchange between air masses from midlatitudes and polar regions. During the second phase of the NETCARE 2014 measurements a pronounced low pressure system south of Resolute Bay brought inflow from southern latitudes that pushed the polar dome northward and significantly affected trace gas mixing ratios in the measurement region. Mean CO mixing ratios increased from 77.9 ± 2.5 ppbv to 84.9 ± 4.7 ppbv from the first period to the second period. At the same time CO2 mixing ratios significantly dropped from 398.16 ± 1.01 ppmv to 393.81 ± 2.25 ppmv. We further analysed processes controlling the recent transport history of air masses within and outside the polar dome. Air masses within the spring time polar dome mainly experienced diabatic cooling while travelling over cold surfaces. In contrast air masses in the summertime polar dome were diabatically heated due to insolation. During both seasons air masses outside the polar dome slowly descended into the Arctic lower troposphere from above caused by radiative cooling. The ascent to the middle and upper troposphere mainly took place outside the Arctic, followed by a northward motion. Our results demonstrate the successful application of a tracer based diagnostic to determine the location of the polar dome boundary.

scholarly journals Metagenomic Analysis of Stress Genes in Microbial Mat Communities from Antarctica and the High Arctic

2011 ◽  
Vol 78 (2) ◽  
pp. 549-559 ◽  
Author(s):  
Thibault Varin ◽  
Connie Lovejoy ◽  
Anne D. Jungblut ◽  
Warwick F. Vincent ◽  
Jacques Corbeil
Keyword(s):  
High Arctic ◽  
Environmental Stresses ◽  
The Arctic ◽  
Functional Responses ◽  
Protein Coding ◽  
Content Type ◽  
Stress Genes ◽  
Cyanobacterial Genes ◽  
Shock Proteins ◽  
The Antarctic

ABSTRACTPolar and alpine microbial communities experience a variety of environmental stresses, including perennial cold and freezing; however, knowledge of genomic responses to such conditions is still rudimentary. We analyzed the metagenomes of cyanobacterial mats from Arctic and Antarctic ice shelves, using high-throughput pyrosequencing to test the hypotheses that consortia from these extreme polar habitats were similar in terms of major phyla and subphyla and consequently in their potential responses to environmental stresses. Statistical comparisons of the protein-coding genes showed similarities between the mats from the two poles, with the majority of genes derived fromProteobacteriaandCyanobacteria; however, the relative proportions differed, with cyanobacterial genes more prevalent in the Antarctic mat metagenome. Other differences included a higher representation ofActinobacteriaandAlphaproteobacteriain the Arctic metagenomes, which may reflect the greater access to diasporas from both adjacent ice-free lands and the open ocean. Genes coding for functional responses to environmental stress (exopolysaccharides, cold shock proteins, and membrane modifications) were found in all of the metagenomes. However, in keeping with the greater exposure of the Arctic to long-range pollutants, sequences assigned to copper homeostasis genes were statistically (30%) more abundant in the Arctic samples. In contrast, more reads matching the sigma B genes were identified in the Antarctic mat, likely reflecting the more severe osmotic stress during freeze-up of the Antarctic ponds. This study underscores the presence of diverse mechanisms of adaptation to cold and other stresses in polar mats, consistent with the proportional representation of major bacterial groups.

scholarly journals A Machine Learning Approach for Estimating the Trophic State of Urban Waters Based on Remote Sensing and Environmental Factors

2021 ◽  
Vol 13 (13) ◽  
pp. 2498
Author(s):  
Shijie Zhu ◽  
Jingqiao Mao
Keyword(s):  
Remote Sensing ◽  
Environmental Factors ◽  
Water Temperature ◽  
Trophic State ◽  
Trophic Levels ◽  
Water Bodies ◽  
Trophic State Index ◽  
Urban Water ◽  
Estimation Model ◽  
Input Variables

To improve the accuracy of remotely sensed estimates of the trophic state index (TSI) of inland urban water bodies, key environmental factors (water temperature and wind field) were considered during the modelling process. Such environmental factors can be easily measured and display a strong correlation with TSI. Then, a backpropagation neural network (BP-NN) was applied to develop the TSI estimation model using remote sensing and environmental factors. The model was trained and validated using the TSI quantified by five water trophic indicators obtained for the period between 2018 and 2019, and then we selected the most appropriate combination of input variables according to the performance of the BP-NN. Our results demonstrate that the optimal performance can be obtained by combining the water temperature and single-band reflection values of Sentinel-2 satellite imagery as input variables (R2 = 0.922, RMSE = 3.256, MAPE = 2.494%, and classification accuracy rate = 86.364%). Finally, the spatial and temporal distribution of the aquatic trophic state over four months with different trophic levels was mapped in Gongqingcheng City using the TSI estimation model. In general, the predictive maps based on our proposed model show significant seasonal changes and spatial characteristics in the water trophic state, indicating the possibility of performing cost-effective, RS-based TSI estimation studies on complex urban water bodies elsewhere.

Size-fractionated surface phytoplankton in the Kara and Laptev Seas: environmental control and spatial variability

2021 ◽  
Vol 664 ◽  
pp. 59-77
Author(s):  
AB Demidov ◽  
IN Sukhanova ◽  
TA Belevich ◽  
MV Flint ◽  
VI Gagarin ◽  
...  
Keyword(s):  
Spatial Variability ◽  
Primary Production ◽  
Water Temperature ◽  
Environmental Control ◽  
Size Structure ◽  
Total Carbon ◽  
The Arctic ◽  
Size Groups ◽  
Phytoplankton Size ◽  
Phytoplankton Size Structure

Climate-induced variability of phytoplankton size structure influences primary productivity, marine food web dynamics, biosedimentation and exchange of CO2 between the atmosphere and ocean. Investigation of phytoplankton size structure in the Arctic Ocean is important due to rapid changes in its ecosystems related to increasing temperature and declining sea ice cover. We estimated the contribution of surface micro-, nano- and picophytoplankton to the total carbon biomass, chlorophyll a concentration and primary production in the Kara and Laptev Seas and investigated the relationships of these phytoplankton size groups with environmental factors which determine their spatial variability. Additionally, we compared chlorophyll specific carbon fixation rate, specific growth rate and carbon to chlorophyll ratios among different phytoplankton size groups. The investigation was carried out from August to September 2018. Generally, picophytoplankton was dominant in terms of chlorophyll a and primary production in the whole study area. The spatial variability of phytoplankton size classes was influenced by river discharge and relied mainly on water temperature, salinity and dissolved silicon concentration. Microphytoplankton prevailed across the river runoff region under conditions of low salinity and relatively high water temperature, while picophytoplankton was predominant under conditions of high salinity and low water temperature. Our study is the first to characterize size-fractionated phytoplankton abundance in the Kara and Laptev Seas, and provides a baseline for future assessment of the response of Kara and Laptev Sea ecosystems to climate-induced processes using phytoplankton size structure.

Phytoplankton of cold-water lake ecosystems under the influence of natural and anthropogenic factors

2021 ◽  
pp. 42-49
Author(s):  
Andrey N. Sharov
Keyword(s):  
Heavy Metals ◽  
Cold Water ◽  
Arctic Lakes ◽  
Water Bodies ◽  
The Arctic ◽  
Anthropogenic Factors ◽  
Large Lakes ◽  
Arctic Water ◽  
The North ◽  
Natural And Anthropogenic Factors

Based on the study of the spatio-temporal aspects of the development of phytoplankton in the lakes of the North and North-West of the European territory of Russia (large lakes – Imandra, Onega and Chudsko-Pskovskoye and small lakes of the Arctic and Subarctic), the features of its structure and dynamics under the influence of natural and anthropogenic factors (eutrophication, heavy metal pollution, acidification, thermification). The species composition and quantitative characteristics of phytoplankton of large lakes of the North of Russia, small arctic lakes and lakes of subarctic regions are studied. It has been shown that diatoms predominate in arctic water bodies according to species diversity, and green and diatoms predominate in boreal ones. By biomass, diatoms dominate mainly in all cold-water lakes, with the exception of small arctic lakes, where golden algae lead. The features of the reorganization of phytoplankton in response to the action of anthropogenic factors are revealed. It is proved that in the northern water bodies the complex action of heavy metals and nutrients does not lead to inhibition of phytoplankton, and the effect of acidification in combination with heavy metals enhances the toxic effect of the latter. A feature of the response to acidification is an increase in the variability of the dynamics of the biomass of phytoplankton. It has been shown that in different types of lakes of East Antarctica under severe climate conditions under light and biogenic limitation, redistribution of autotrophic components in the formation of the biota of water bodies occurs: against the background of a decrease in the abundance and diversity of phytoplankton, the role of microphytobenthos and periphyton increases.

Zooplankton dynamics during autumn circulation in a small, wind-sheltered, Mediterranean lake

2006 ◽  
Vol 57 (4) ◽  
pp. 441 ◽  
Author(s):  
M. Alvarez-Cobelas ◽  
A. Baltanás ◽  
J. L. Velasco ◽  
C. Rojo
Keyword(s):  
Water Temperature ◽  
Current Model ◽  
Fish Predation ◽  
Controlling Factors ◽  
Heterotrophic Nanoflagellates ◽  
Delayed Effects ◽  
Zooplankton Dynamics ◽  
Mediterranean Lake ◽  
Fish Abundances ◽  
Ceriodaphnia Reticulata

Few studies have been undertaken on zooplankton dynamics during the transition from late stratification to early mixing in lakes. The Plankton Ecology Group (PEG) model of plankton seasonality only considers water temperature, edible phytoplankton and fish predation as zooplankton-controlling factors during that period. The water-column edible algal and bacterial fractions, heterotrophic nanoflagellates, ciliates, rotifers, cladocerans and copepods were studied during 93 consecutive days of mixing-transition in a wind-sheltered, Mediterranean lake without planktivorous fish. Abundances of all zooplankton populations except ciliates, Daphnia longispina and copepodites, were related to water temperature. In addition to PEG controlling factors, time series analysis indicated competition between ciliates and Ceriodaphnia reticulata and Polyarthra dolichoptera and D. longispina, predation of Arctodiaptomus salinus on ciliates, herbivory of adult copepods on the 5–20 μm phytoplanktonic size and delayed effects shorter than one week. The remaining zooplankton populations did not show any edible size preference. Ceriodaphnia reticulata showed evidence of herbivory on bacteria and picoplankton and competition with Hexarthra fennica in shorter periods. Phyto- and zooplankton production were decoupled. These results, and others from warmer periods and latitudes, suggest that the current model of lake plankton seasonality must be reviewed.

scholarly journals The Rossby radius in the Arctic Ocean

Ocean Science ◽  
2014 ◽  
Vol 10 (6) ◽  
pp. 967-975 ◽  
Author(s):  
A. J. G. Nurser ◽  
S. Bacon
Keyword(s):  
Arctic Ocean ◽  
General Circulation ◽  
Circulation Model ◽  
Ocean General Circulation Model ◽  
High Arctic ◽  
The Arctic ◽  
Hudson Bay ◽  
Ocean Eddies ◽  
Shelf Seas ◽  
The Impact

Abstract. The first (and second) baroclinic deformation (or Rossby) radii are presented north of ~60° N, focusing on deep basins and shelf seas in the high Arctic Ocean, the Nordic seas, Baffin Bay, Hudson Bay and the Canadian Arctic Archipelago, derived from climatological ocean data. In the high Arctic Ocean, the first Rossby radius increases from ~5 km in the Nansen Basin to ~15 km in the central Canadian Basin. In the shelf seas and elsewhere, values are low (1–7 km), reflecting weak density stratification, shallow water, or both. Seasonality strongly impacts the Rossby radius only in shallow seas, where winter homogenization of the water column can reduce it to below 1 km. Greater detail is seen in the output from an ice–ocean general circulation model, of higher resolution than the climatology. To assess the impact of secular variability, 10 years (2003–2012) of hydrographic stations along 150° W in the Beaufort Gyre are also analysed. The first-mode Rossby radius increases over this period by ~20%. Finally, we review the observed scales of Arctic Ocean eddies.

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