Glacial River Research Articles

Formation of glacier runoff on the northern slope of Tavan Bogd mountain massif based on stable isotopes data

This investigation is based on measurements of stable isotopes concentrations (δD and δ18О) in water, snow and ice samples. Glaciers are composed of ice, snow, and fi n of atmospheric origin. The isotopic composition of these components is different, so when melting they form the melted glacial water with different isotope characteristics. Summer precipitation contains the heaviest isotopes, but only a small part of them remains on the glacier. The average isotopic composition of glacier ice represents the average composition of precipitation that accumulates on it. However, snow and fi n of different seasons can occur on the glacier surface, the isotopic composition of which differs from the isotopic composition of glacier ice. At different times of the ablation season different parts of the glacier melt, therefore the isotopic composition of melt waters will be different. Differences in the isotopic composition of the major runoff-forming components on the Northern slopes of the massif Tabyn-Bogdo-Ola had been identified. A part of melting ice in the formation of the runoff on this massif is determined by estimation of the isotopic composition of snow, ice, and fi n on different glaciers of this region. The average δ18О of snow on the glacier surface is −11.9‰, and this snow can be attributed to the precipitation fallen in late spring or early summer. Measured average isotopic composition of precipitation (δ18О = −11.9‰) was compared with the online calculator of the isotope content in precipitation (OIPC). The isotopic composition of glacial melt waters on the Northern macro-slope in the middle of July 2015 (δ18О = −15.3‰) differs from the isotopic composition of the territory of the Mongolian part of the massif (δ18О = −17.4‰) obtained from results of the analysis of eight samples taken at different edges of the glaciers at the beginning of August 2013. Isotopic separation shows important role of summer snow in feeding the glacial rivers of the massif even in the middle of the ablation season, especially for glaciers in the central part of the massif. The role of seasonal snow in feeding the glacier streams depends on the morphological type of glacier. It is maximum for corrie glaciers and minimum for the valley ones.

Spatial and temporal variations in river terrace formation, preservation, and morphology in the Lower Meuse Valley, The Netherlands

AbstractThe Lower Meuse Valley crosses the Roer Valley Rift System and provides an outstanding example of well-preserved late glacial and Holocene river terraces. The formation, preservation, and morphology of these terraces vary due to reach-specific conditions, a phenomenon that has been underappreciated in past studies. A detailed palaeogeographic reconstruction of the terrace series over the full length of the Lower Meuse Valley has been performed. This reconstruction provides improved insight into successive morphological responses to combined climatic and tectonic external forcing, as expressed and preserved in different ways along the river. New field data and data obtained from past studies were integrated using a digital mapping method in GIS. Results show that late glacial river terraces with diverse fluvial styles are best preserved in the Lower Meuse Valley downstream sub-reaches (traversing the Venlo Block and Peel Block), while Holocene terrace remnants are well-developed and preserved in the upstream sub-reaches (traversing the Campine Block and Roer Valley Graben). This reach-to-reach spatial variance in river terrace preservation and morphology can be ascribed to tectonically driven variations in river gradient and subsurface lithology, and to river-driven throughput of sediment supply.

The effects of different land use and hydrological types on water chemistry of young glacial ponds

The study aims to examine the effect of ponds on changes in water quality in a young glacial river catchment. The goal was to identify situations where a periodic hydrographic network is formed in outflow-free areas, which is connected with a higher order receiving area, as well as to study the circulation of matter in this type of system. This study answers the following key question: Do ponds affected by areal pollution substantially affect water quality in streams in periods where they become joined with the hydrographic network? The purpose of the research was to identify patterns associated with the functioning of ponds in young glacial areas in northern Poland on the example of the Borucinka catchment. Ponds were selected in order to generate a study sample characterized by different types of land use, local hydrology, and pond surface area. The study focused on the effects of catchment land use on pond water quality and the effects of periodic changes in local hydrology (linkage of surface flows with bodies of water) on pond water quality. Research has shown that land use in a pond catchment yields a substantial effect on pond water quality. The basic reason for the higher concentration of selected ions is close proximity to farms that generate wastewater, which reaches bodies of water in the study area. Seasonal changes in the concentration of biogenic substances were not observed in ponds. Only notable changes in the concentration of total nitrogen were observed due the episodic formation of a hydrographic network consisting of a collection of linked depressions. One of the more surprising findings was that permanently isolated ponds, which theoretically collect catchment pollutants all the time, are characterized by good hydrochemical conditions.

Environmental context and adaptations of prehistoric and early historical occupation in the Southern Altai (SW Siberia\u2013East Kazakhstan)

The Altai Mountains are well-known for their unique archaeological records, with rich, chronologically sequenced Palaeolithic, Neolithic and the Bronze Age (late fourth–early first millennium BC) sites and, in particular, the Iron Age Scytho-Siberian and early historical monuments represented by burial sites, ritual structures, and rock-art. The Altai prehistoric archaeological localities are distributed across a broad range of topographic and ecological settings, encompassing altitudinal zones from 800 m asl in the lower reaches of glacial river valleys up to 2500/3000 m asl on the high mountain plateaus. The partial spatial overlap of these (often multi-component) geoarchaeological loci over time suggests that similar adaptive strategies were employed by countless generations of hunter and later nomadic communities—their actions constrained by the locally specific forms of (palaeo-)relief and the associated ecosystems. The dynamics of the initial occupation of the boreal and alpine Altai landscapes and subsequent processes of (re-)colonisation during the Final Pleistocene-Holocene transition are directly linked to transformations in the regional hydrological systems after the LGM. The principal settings for early pastoral settlements were the xerothermic grasslands that formed on the flat glacio-lacustrine terraces which rise above the modern fluvial floodplains—the remains of ice-dammed wastage lake basins drained at the end of the Pleistocene (15,000–13,000 year BP). Marked climatic changes, evidenced by regional variations in temperature and humidity across the territory, are well attested in the geological, biotic and archaeological records. The initial Sub-Boreal aridification correlated with the beginnings of the Altai Bronze Age traditions continued until the early Iron Age—causing an expansion of parkland-steppe in the main valleys and a forest retreat in the foothills. Mountain steppes constituted the most essential food-procurement habitat for the Holocene prehistoric and historical settlements of Southern Altai. The current degradation of insular alpine permafrost poses an imminent threat to preservation of the region’s most precious archaeological monuments—the frozen burial mounds of the Pazyryk culture (sixth–third century BC) belonging to the UNESCO World cultural heritage.

Rare Glacial River Drains Potentially Harmful Lakes

Antarctic lakes have contributed to ice shelf breakup in the past, but a glacier in Greenland appears safe from a similar fate, thanks to a river that drains away water.

After the ice: Lateglacial and Holocene landforms and landscape evolution in Scotland

ABSTRACTDuring Lateglacial cold periods, permafrost developed throughout Scotland, sediment-mantled slopes were extensively modified by solifluction and other forms of periglacial mass movement, large-scale sorted patterned ground formed on plateaux, and enhanced rockfall resulted in talus accumulation below cliffs. Most rock-slope failures occurred within five millennia following ice-sheet deglaciation, with many probably triggered by uplift-induced earthquakes; numerous debris-free scarps represent sites where Lateglacial rockslide debris was excavated by glaciers during the Younger Dryas Stade (∼12.9–11.7 ka). Sandar and outwash fans deposited by glacial rivers during ice-sheet retreat were incised to form high-level terraces. Under the cool temperate but relatively stable climate of the Holocene, solifluction and patterned ground formation continued to operate on high ground, though accumulation of high-level aeolian deposits on most mountains was terminated by erosion during the Little Ice Age. Drift-mantled slopes and talus slopes have been extensively eroded by translational failures and debris flows, the latter depositing debris cones on upland valley floors. The incidence of Holocene rockslides has been much lower than during the Lateglacial period. Dating of alluvial deposits and low Holocene terraces suggests no consistent pattern of Holocene floodplain evolution: incision has apparently dominated in the Highlands, aggradation in the lowlands, and floodplains in the Southern Uplands have asynchronous histories of incision and aggradation. Studies of floodplain behaviour over the past 200–300 years suggest that though major floods rework the floodplains of braided and piedmont rivers, there is no tendency towards net floodplain aggradation or incision. Most valley-side alluvial fans accumulated episodically in the last 4000 years, many in response to lowering of hillslope stability by woodland clearance. For many postglacial landsystems, disentangling the effects of declining paraglacial sediment supply, climate change and local influences (extreme rainstorm events or anthropogenic impacts) remains challenging.

Map of the terminal moraine of the Werenskioldbreen glacier (South-West Spitsbergen) from 2015

The first direct field measurement of the entire terminal moraine of the Werenskioldbreen glacier on Spitsbergen took place at the end of July and the beginning of August 2015. The results of the measurements were the basis for the development of the large-scale terminal moraine map. The article presents the stages of map creation and editing based on measurement points established by the GNSS method. The map editing required knowledge of the morphologically complex terrain. Key documentation was field notes and documentary photographs, enabling the cartographic interpretation of the varied topographic features of the terrain's surface. Based on the documentation, the water bodies on the moraine were located, the outline of the structure and the boundary points were executed and the latter were excluded from the triangulation process. The glacial river was also excluded from triangulation, which allowed a DTM to be developed. An important step in point cloud mapping was to generate a topologically correct digital elevation model of satisfactory accuracy. On the basis of the DTM, contour lines were generated showing the topographic features of the terrain's surface. The printable resultant map's scale is 1: 5000; it is in the UTM coordinate system, in the 33X zone. Complementing the content of the map, a grid of geographic coordinates, a kilometer grid, and map key descriptions were added.

Stream temperature dynamics in Nam Co basin, southern Tibetan Plateau

Stream temperatures are sensitive to climate change and runoff regime variations. A comprehensive understanding on the effects of glacial melting on the stream temperatures are important in the Tibetan Plateau, of which contains the largest ice volume outside Polar Regions. This study documented the high-resolution stream temperature thermal regimes from glacier-fed and non-glacial rivers at four sites, versus a high-resolution glacier mass balance monitoring at Zhadang glacier, during summer melt seasons from 2007‒2009 in the Nam Co basin of southern Tibetan Plateau. The results showed mean summer stream temperature and magnitude of daily thermal variation were lower at all sites when compared with alpine glacierized environments at lower latitudes. Mean stream temperatures for glacier-fed rivers (4.0°C to 6.5°C) were minimum and least variable near the glacier terminus with increasing toward downstream (+0.13°Ckm–1 to +0.28°C km–1). Meanwhile, stream temperature in 2008 was similar to that in 2007 and 2009. For the non-glacial rivers, mean stream temperatures was about 9.0°C with significantly warmer in summer months in 2009 and 2007 than that in 2008. These differences indicated that stream temperature was strongly influenced by discharge and precipitation. Particularly, the glacier mass balance played a large role on the stream temperature directly when the glacier melt contributed more than 50% of the glacial river runoff. Our results demonstrated the stream thermal variability from southern Tibetan rivers and provided new insight into the influence of glacier mass balance on stream thermal variability in high-altitude river system.

Impact of glacial activity on the weathering of Hf isotopes – Observations from Southwest Greenland

Data for the modern oceans and their authigenic precipitates suggest incongruent release of hafnium (Hf) isotopes by chemical weathering of the continents. The fact that weathering during recent glacial periods is associated with more congruent release of Hf isotopes has led to the hypothesis that the incongruency may be controlled by retention of unradiogenic Hf by zircons, and that glacial grinding enhances release of Hf from zircons. Here we study the relationship between glacial weathering processes and Hf isotope compositions released to rivers fed by land-terminating glaciers of the Greenland Ice Sheet, as well as neighbouring non-glacial streams. The weathered source rocks in the studied area mostly consist of gneisses, but also include amphibolites of the same age (1.9Ga). Hafnium and neodymium isotope compositions in catchment sediments and in the riverine suspended load are consistent with a predominantly gneissic source containing variable trace amounts of zircon and different abundances of hornblende, garnet and titanite.Glacially sourced rivers and non-glacial streams fed by precipitation and lakes show very unradiogenic Nd isotopic compositions, in a narrow range (ɛNd=−42.8 to −37.9). Hafnium isotopes, on the other hand, are much more radiogenic and variable, with ɛHf between −18.3 and −0.9 in glacial rivers, and even more radiogenic values of +15.8 to +46.3 in non-glacial streams. Although relatively unradiogenic Hf is released by glacial weathering, glacial rivers actually fall close to the seawater array in Hf-Nd isotope space and are not distinctly unradiogenic.Based on their abundance in rocks and sediments and their isotope compositions, different minerals contribute to the radiogenic Hf in solution with a decreasing relevance from garnet to titanite, hornblende and apatite. Neodymium isotopes preclude a much stronger representation of titanite, hornblende and apatite in solution, such as might result from differences in dissolution rates, than estimated from mineral abundance. The strong contrast in Hf isotope compositions between glacial rivers and non-glacial streams results mostly from different contributions from garnet and zircon, where zircon weathering is more efficient in the subglacial environment.A key difference between glacial and non-glacial waters is the water-rock interaction time. While glacial rivers receive continuous contributions from long residence time waters of distributed subglacial drainage systems, non-glacial streams are characterized by fast superficial drainage above the permafrost horizon. Therefore, the increased congruency in Hf isotope weathering in glacial systems could simply reflect the hydrological conditions at the base of the ice-sheet and glaciers, with zircon weathering contributions increasing with water-rock interaction time.

Carbon Bioavailability in a High Arctic Fjord Influenced by Glacial Meltwater, NE Greenland

The land-to-ocean flux of organic carbon is increasing in glacierized regions in response to increasing temperatures in the Arctic (Hood et al., 2015). In order to understand the response in ecosystem metabolism to the organic carbon input it is essential to determine the bioavailability of the different carbon sources in the system. We quantified the bacterial turnover of organic carbon in a high Arctic fjord system (Young Sound, NE Greenland) during the ice-free period (July-October 2014) and assessed the quality and quantity of the 3 major organic carbon sources; 1) local phytoplankton production 2) runoff from land-terminating glaciers and a lowland river and 3) inflow from the ocean shelf. We found that despite relatively low concentrations of DOC in the rivers, the bioavailability of the river–DOC was significantly higher than in the fjord, and characterized by high cell-specific bacterial production and low C:N ratios. In contrast, the allochthonous DOC source entering via inflow of coastal shelf waters had elevated DOC concentrations with low bioavailability, high C:N and low specific bacterial production. The phytoplankton production in the fjord could not sustain the bacterial carbon demand, but was still the major source of organic carbon for bacterial growth. We assessed the bacterial community composition and found that communities were specific for the different water types i.e. the bacterial community of the coastal coastal inflow water could be traced mainly in the subsurface water, while the glacial river community strongly dominated the surface water in the fjord.

Continental weathering and terrestrial (oxyhydr)oxide export: Comparing glacial and non-glacial catchments in Iceland

Glaciers enhance terrestrial erosion and sediment export to the ocean. Glaciers can also impact mineral specific weathering rates relative to analogous non-glacial terrains. In tandem these processes affect continent sediment export to the oceans over glacial-interglacial cycles. This study summarizes field data from glacial and non-glacial Icelandic river catchments to quantify the impact of weathering regime on iron and aluminium (oxyhydr)oxide mineral formation and flux rates. Aluminium and iron (oxyhydr)oxides are strong indicators of organic carbon preservation in soils and marine sediments. Tracing changes in (oxyhydr)oxide formation and deposition therefore provides a means of evaluating potential changes in organic carbon sequestration rates over glacial-interglacial cycles. Overall, there are several measurable chemical differences between the studied glacial and non-glacial catchments which reflect the key role of soil formation on terrestrial weathering. One of the noted chemical differences is that weathering in non-glacial catchments is characterized by higher apparent rates of iron and aluminium (oxyhydr)oxide formation relative to glacial catchments. However, the offset in (oxyhydr)oxide formation does not appear to be transferred into river sediment compositions, and physical weathering appears to be the dominant control of river sediment composition and export. Glacial rivers export far more total sediment to nearshore marine environments than analogous non-glacial rivers suggesting glacial weathering enhances carbon burial by increasing nearshore marine (oxyhydr)oxide accumulation.

Marine birds and mammals foraging in the rapidly deglaciating Arctic fjord - numbers, distribution and habitat preferences

Climate-induced glacier retreat is considered in the context of its reducing the sea-ice contact zone used by marine birds and mammals as important foraging grounds and may cause declines in their numbers. To test this hypothesis, a survey was conducted in diversified habitats of a rapidly deglaciating Arctic fjord in Svalbard. Of the fifteen seabird and four mammal species found, coastal surface-feeders prevailed over benthic-feeders and pelagic pursuit-divers. Deep tidewater glacier bays were used by the most numerous but least heterogeneous foraging community, in contrast to the shallow lagoons of coastline-terminating glaciers and deglaciated shorelines. After the 15 years of glaciers retreat documented in Hornsund, the sea-ice contact zone used by birds and mammals has not declined. On the contrary, the increasing freshwater supply from underwater glacial rivers raising zooplankton up to the surface, thus making it available to seabirds, enhances the attractiveness of tidewater glacier bays. Along with the stage of retreat, the importance of glacier bays as feeding grounds changes. Foraging conditions deteriorate when the glacier terminus reaches the coastline and the glacier bay becomes shallower. However, glacier retreat enlarges the area of littoral habitats accessible to benthophages. Glacier-related habitats situated close to colony are used as alternative/emergency feeding grounds by seabirds that normally forage outside the fjord. This is especially important during the chick-rearing period and also during bad weather conditions in the open sea. Our study demonstrates that, so far, the abundance and species diversity of seabirds foraging in the rapidly deglaciating Hornsund are both high, suggesting that they benefit from the current intensive glacier melt. However, with further climate change an apparent biodiversity paradox may occur. Here, overall biodiversity will increase but local diversity of pagophilic species will decline. Such nonlinear responses complicate the prediction of future polar ecosystem dynamics.

Variability of macroelements content in soils of a young glacial river valley - a geochemical landscape approach

Variability of macroelements content in soils of a young glacial river valley - a geochemical landscape approach

RIVER ECOLOGICAL STUDY: BUILDING THE KNOWLEDGE BASE FOR VARIETY OF ASSESSMENTS SUCH AS CLIMATE CHANGE IN NEPAL

Climate change is now universally acknowledged to be taking place across the globe. It is generally presumed that the impacts of climate change would be more severe in the country like Nepal due to its location, physiography, poverty and lack of preparedness to cope with the changes. The last reason is mainly associated with knowledge, information and ability to use technologies based on science.The main objective of this research is to analyze and evaluate the effects of climate change by taking fish as an indicator. However, an even more important outcome is to prepare a solid foundation of fish-based information, which could be used in the future as a reference for a variety of purposes including the study of climate change. Two sets of examples, one in the tributaries of a glacial river and another in the tributary of a rain -fed river are compared in terms of fish ecological attributes to test for effects of climate change. In addition to fish-based information, this research also studies physico-chemical parameters and benthic fauna so as to build up an ecological profile of the rivers.

A melting glacier feeds aquatic and terrestrial invertebrates with ancient carbon and supports early succession

ABSTRACTMore than 5000-yr-old organic material was released by a melting glacier in central southern Norway. The ancient carbon was bioavailable and supported early food chains. This was shown through high radiocarbon age in living aquatic and terrestrial invertebrates. Young ponds acted as biological oases, where ancient carbon was assimilated by larvae of various Diptera: mainly Chironomidae, but also Tipulidae and Limoniidae. Within ponds, even predatory diving beetles had a high radiocarbon age. Adult chironomid midges with a radiocarbon age of 1040 yr transported ancient carbon to terrestrial predators among beetles, spiders, and harvestmen. Ancient carbon was also assimilated by chironomid larvae downstream in the glacier-fed river, and radiocarbon dating of chironomid larvae from glacial rivers will thus be an easy way to check whether a given glacier releases bioavailable ancient carbon. Our study indicates that the ancient organic particles were very small. We refer to studies from other countries showing that glaciers collect and release ancient carbon in the form of tiny, long-transported and biodegradable aerosol particles, which stem from the incomplete combustion of radiocarbon-depleted fossil fuels. All our results would fit with this mechanism.

First spatio-temporal study of macroinvertebrates in the Santa Cruz River: a large glacial river about to be dammed without a comprehensive pre-impoundment study

The Santa Cruz River is the last free-flowing river in Argentinean Patagonia. Two dams are projected, and no comprehensive pre-impoundment study has been undertaken. The present study investigated macroinvertebrate communities along three different hydrological periods and at three river sections located upstream and downstream of future dams. Fifty-three macroinvertebrate taxa were identified, with the most abundant orders being Ephemeroptera, Plecoptera, Coleoptera, and Crustacea (particularly amphipods). Ordination methods (CCA) and generalized linear models (GLM) were applied. According to the CCA, the main environmental variables related to macroinvertebrate density were temperature, suspended solids, depth, and substrate size. For the GLM, the main factors associated with macroinvertebrate abundance were location and hydrological period, and variables with the highest influences were temperature, substrate size, current speed, and depth. We anticipate that dam construction will modify in-stream habitat conditions, leading to changes in (i) macroinvertebrate community structure and (ii) local fish abundance due to loss of key prey taxa.

Two approaches to hydrograph separation of the glacial river runoff using isotopic methods

Application of the stable isotope method in the balance equations used to calculate separation of the runoff hydrograph from the Djankuat Glacier basin is demonstrated. Simultaneous solution of equations of water, isotope and ion balances is applied to estimate contributions of different components and processes to formation of the Djankuat River runoff regime. For June 2014, we made calculations for the purpose to separate contributions of the spring (isotopically weighted) snow and winter (isotopically depleted) snow. Field works in the glacial basin Djankuat were performed during two ablation seasons, i.e. from June to September of 2013 and 2014. Two approaches were used when calculating separation of the runoff hydrograph by means of solution of systems of equations for isotopic and ion balances: 1) taking account of the isotope fractionation during snow melting, and 2) with no account for the fractionation. Separation of the hydrograph for June 2014 have shown that about 15–20% of the Djankuat River runoff is formed by spring snow melting, sometimes increasing up to 36%. Contribution of spring meltwater to the total runoff increases when the isotope fractionation during the snow melting is taken into account for the calculations. In this case, the contribution of spring snow changes from 30 to 50%.

Stable oxygen isotope variability in two contrasting glacier river catchments in Greenland

Abstract. Analysis of stable oxygen isotope (δ18O) characteristics is a useful tool to investigate water provenance in glacier river systems. In order to attain knowledge on the diversity of δ18O variations in Greenlandic rivers, we examined two contrasting glacierised catchments disconnected from the Greenland Ice Sheet (GrIS). At the Mittivakkat Gletscher river, a small river draining a local temperate glacier in southeast Greenland, diurnal oscillations in δ18O occurred with a 3 h time lag to the diurnal oscillations in run-off. The mean annual δ18O was −14.68 ± 0.18 ‰ during the peak flow period. A hydrograph separation analysis revealed that the ice melt component constituted 82 ± 5 % of the total run-off and dominated the observed variations during peak flow in August 2004. The snowmelt component peaked between 10:00 and 13:00 local time, reflecting the long travel time and an inefficient distributed subglacial drainage network in the upper part of the glacier. At the Kuannersuit Glacier river on the island Qeqertarsuaq in west Greenland, the δ18O characteristics were examined after the major 1995–1998 glacier surge event. The mean annual δ18O was −19.47 ± 0.55 ‰. Despite large spatial variations in the δ18O values of glacier ice on the newly formed glacier tongue, there were no diurnal oscillations in the bulk meltwater emanating from the glacier in the post-surge years. This is likely a consequence of a tortuous subglacial drainage system consisting of linked cavities, which formed during the surge event. Overall, a comparison of the δ18O compositions from glacial river water in Greenland shows distinct differences between water draining local glaciers and ice caps (between −23.0 and −13.7 ‰) and the GrIS (between −29.9 and −23.2 ‰). This study demonstrates that water isotope analyses can be used to obtain important information on water sources and the subglacial drainage system structure that is highly desired for understanding glacier hydrology.

Hydrodynamic processes and depositional styles of glacier-associated deposits in the Moxi basin, Southwest China

This study aims to understand the particle size distribution and depositional styles of glacier-associated deposits in the Moxi basin in southwest China. Based on field surveys, 28 samples from glacier-associated deposits (including glacial till, fluvioglacial, debris flow, river and lake deposits) were collected and tested in the laboratory. The results showed that the glacier-associated deposits can be differentiated based on particle gradation, particle size distribution and accumulated percentages. We evaluated the evolution of a former dammed lake in the Moxi basin based on glacier-associated deposits. The results of this study also indicated that the Moxi Platform was not formed by a single depositional process but is composed of both fluvioglacial and debris flow deposits. This research shows that the depositional style analysis is useful in identifying different glacier-associated deposits in high mountain regions. Moreover, the evaluation of the differences in particle sizes of the glacierassociated deposits is useful in reconstructing geohazard events in periglacial regions, and this information can help in identifying and reducing the potential risks associated with geo-hazards.

Growth and Smoltification of Three Norwegian Strains of Atlantic Salmon Salmo salar Reared under Different Thermal Regimes

AbstractA comparative study was performed with juvenile Atlantic salmon Salmo salar from three stocks in Western Norway that differ in their natural conditions. One is from warm, lowland river conditions (Årdal), one is from cold glacial river conditions (Stryn) and the last one (Suldalslågen) is from a hydropower‐regulated river. The salmon parr were tagged and reared at 4, 5.5 and 7 °C and simulated natural water temperature (SNT) for river Suldalslågen. Size distribution was unimodal at 4 °C, with a change to a bimodal distribution, representing potential 1+ and 2+ smolts, at the other temperature regimes. The relative biomass of 1+ smolts varied between the stocks as Stryn (cold glacial river) stock had the highest number of smolts at 7 °C and the Suldalsågen stock (hydropower‐regulated river) displaying the highest number at the SNT regime. Overall, the Stryn stock, originating from cold river conditions, seemed to be well adapted to growth and smoltification at cold temperatures, whereas salmon parr from river Suldalslågen seem to be better adapted to the natural temperature regime (SNT) of this river than the other two stocks. This was reflected in the gill Na+,K+‐ATPase as the Suldalslågen stock showed increasing activity from 16 April (4.2 µmol ADP mg protein−1 h−1) to 10 May (9.2 µmol ADP mg protein−1 h−1), and at the end of the experiment, enzyme activity in Suldalslågen stock was significantly higher than both Stryn (5.7) and Årdal (5.9 µmol ADP mg protein−1 h−1) stock. In contrast, the warm lowland stock, Årdal, fish had low Na+,K+‐ATPase activity with no distinct peak at any of the sampled dates from March through May. Copyright © 2016 John Wiley & Sons, Ltd.