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Effects of multiple stresses hydropower, acid deposition and climate change on water chemistry and salmon populations in the River Otra, Norway

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AbstractMany surface waters in Europe suffer from the adverse effects of multiple stresses. The Otra River, southernmost Norway, is impacted by acid deposition, hydropower development and increasingly by climate change. The river holds a unique population of land-locked salmon and anadromous salmon in the lower reaches. Both populations have been severely affected by acidification. The decrease in acid deposition since the 1980s has led to partial recovery of both populations. Climate change with higher temperatures and altered precipitation can potentially further impact fish populations. We used a linked set of process-oriented models to simulate future climate, discharge, and water chemistry at five sub-catchments in the Otra river basin. Projections to year 2100 indicate that future climate change will give a small but measureable improvement in water quality, but that additional reductions in acid deposition are needed to promote full restoration of the fish communities. These results can help guide management decisions to sustain key salmon habitats and carry out effective long-term mitigation strategies such as liming. The Otra River is typical of many rivers in Europe in that it fails to achieve the good ecological status target of the EU Water Framework Directive. The programme of measures needed in the river basin management plan necessarily must consider the multiple stressors of acid deposition, hydropower, and climate change. This is difficult, however, as the synergistic and antagonistic effects are complex and challenging to address with modelling tools currently available.
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We present the greenhouse gas concentrations for the Representative Concentration Pathways (RCPs) and their extensions beyond 2100, the Extended Concentration Pathways (ECPs). These projections include all major anthropogenic greenhouse gases and are a result of a multi-year effort to produce new scenarios for climate change research. We combine a suite of atmospheric concentration observations and emissions estimates for greenhouse gases (GHGs) through the historical period (1750–2005) with harmonized emissions projected by four different Integrated Assessment Models for 2005–2100. As concentrations are somewhat dependent on the future climate itself (due to climate feedbacks in the carbon and other gas cycles), we emulate median response characteristics of models assessed in the IPCC Fourth Assessment Report using the reduced-complexity carbon cycle climate model MAGICC6. Projected 'best-estimate' global-mean surface temperature increases (using inter alia a climate sensitivity of 3°C) range from 1.5°C by 2100 for the lowest of the four RCPs, called both RCP3-PD and RCP2.6, to 4.5°C for the highest one, RCP8.5, relative to pre-industrial levels. Beyond 2100, we present the ECPs that are simple extensions of the RCPs, based on the assumption of either smoothly stabilizing concentrations or constant emissions: For example, the lower RCP2.6 pathway represents a strong mitigation scenario and is extended by assuming constant emissions after 2100 (including net negative CO 2 emissions), leading to CO 2 concentrations returning to 360 ppm by 2300. We also present the GHG concentrations for one supplementary extension, which illustrates the stringent emissions implications of attempting to go back to ECP4.5 concentration levels by 2250 after emissions during the 21 st century followed the higher RCP6 scenario. Corresponding radiative forcing values are presented for the RCP and ECPs.
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The Atlantic salmon population in the River Otra, southern Norway was lost during the 1960's due to acid rain and industrial and municipal pollution. The industrial and municipal pollution sources were sanitized by 1995. A concurrent reduction in acid deposition has during the last 10 years raised pH from 5.2 to 5.7 and reduced inorganic monomeric Al from 71 to 28g Al L–1 above the industrial area. The water quality improvement resulted in salmon fry again being caught from 1995. Physiological measurements (blood parameters and seawater tolerance) performed on smolts of Atlantic salmon exposed within the river during the spring of 1999 suggests that the smolts were fully smoltified and seawater tolerant, despite having moderate gill morphological changes and having moderate high gill Al concentrations (70–80 g Al g–1 dw). The smolt quality measured suggests that the river again can support a native salmon population, provided no negative change in water quality. Winter episodes and acid tributaries within the watershed can, however, offset the recovery process.
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The River Alta, northern Norway (70°N), was regulated for hydropower in 1987. Densities of juveniles and catches of adult Atlantic salmon have been studied since 1980–1981 to examine the effects of regulation. The need to control environmental variables during electrofishing was emphasized, as flow variables explained up to 42% of the variation in estimated juvenile densities. The number of spawning redds was counted along the river from 1996 to 2005. The annual number of spawning redds was correlated with the catch of multi-sea-winter salmon (predominantly females). In the upper 7km section, just downstream of the power station outlet, juvenile densities were reduced by 80% from pre-regulation levels to minimum levels in 1992–1996. This was followed by partial recovery during 1997–2005, although not entirely back to pre-regulation levels. In contrast, the general trend in the middle part of the river was a linear increase in juvenile densities during 1981–2005. Decreased juvenile densities in the upper section was subsequently followed by reduced catches of adult salmon in this part of the river. The relative catches of smolt year classes migrating to sea in the upper section was reduced by up to 75% from 1991 onwards. Spawning and recruitment in the upper section have increased in recent years, probably back to the introduction of catch-and-release angling and an increase in salmon runs. However, present day smolt production in the upper section is still reduced compared to the middle part of the river, 18years after regulation. The decreased densities of juvenile salmon in the upper section were probably caused by several factors, of which stranding mortality due to sudden drops in the water level and increased winter mortality due to changed environmental conditions, especially reduced ice-cover, may be the most important. In conclusion, the regulation caused a considerable reduction of the salmon production in the upper 16% of salmon reaches, but did not affect the salmon population negatively further downstream. This study illustrates that apparently small environmental disturbances can cause large changes in Atlantic salmon abundance in high latitude populations.
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The present paper reviews the effects of water temperature and flow on migrations, embryonic development, hatching, emergence, growth and life-history traits in light of the ongoing climate change with emphasis on anadromous Atlantic salmon Salmo salar and brown trout Salmo trutta. The expected climate change in the Atlantic is for milder and wetter winters, with more precipitation falling as rain and less as snow, decrease in ice-covered periods and frequent periods with extreme weather. Overall, thermal limits for salmonids are species specific. Scope for activity and growth and optimal temperature for growth increase with temperature to an optimal point before constrain by the oxygen content of the water. The optimal temperature for growth decreases with increasing fish size and varies little among populations within species, whereas the growth efficiency may be locally adapted to the temperature conditions of the home stream during the growth season. Indirectly, temperature influences age and size at smolting through its effect on growth. Time of spawning, egg hatching and emergence of the larvae vary with temperature and selective effects on time of first feeding. Traits such as age at first maturity, longevity and fecundity decrease with increasing temperature whilst egg size increases with temperature. Water flow influences the accessibility of rivers for returning adults and speed of both upstream and downstream migration. Extremes in water flow and temperature can decrease recruitment and survival. There is reason to expect a northward movement of the thermal niche of anadromous salmonids with decreased production and population extinction in the southern part of the distribution areas, migrations earlier in the season, later spawning, younger age at smolting and sexual maturity and increased disease susceptibility and mortality. Future research challenges are summarized at the end of the paper.
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Recent climatic change has been recorded across the globe. Although environmental change is a characteristic feature of life on Earth and has played a major role in the evolution and global distribution of biodiversity, predicted future rates of climatic change, especially in temperature, are such that they will exceed any that has occurred over recent geological time. Climate change is considered as a key threat to biodiversity and to the structure and function of ecosystems that may already be subject to significant anthropogenic stress. The current understanding of climate change and its likely consequences for the fishes of Britain and Ireland and the surrounding seas are reviewed through a series of case studies detailing the likely response of several marine, diadromous and freshwater fishes to climate change. Changes in climate, and in particular, temperature have and will continue to affect fish at all levels of biological organization: cellular, individual, population, species, community and ecosystem, influencing physiological and ecological processes in a number of direct, indirect and complex ways. The response of fishes and of other aquatic taxa will vary according to their tolerances and life stage and are complex and difficult to predict. Fishes may respond directly to climate-change-related shifts in environmental processes or indirectly to other influences, such as community-level interactions with other taxa. However, the ability to adapt to the predicted changes in climate will vary between species and between habitats and there will be winners and losers. In marine habitats, recent changes in fish community structure will continue as fishes shift their distributions relative to their temperature preferences. This may lead to the loss of some economically important cold-adapted species such as Gadus morhua and Clupea harengus from some areas around Britain and Ireland, and the establishment of some new, warm-adapted species. Increased temperatures are likely to favour cool-adapted (e.g. Perca fluviatilis) and warm-adapted freshwater fishes (e.g. roach Rutilus rutilus and other cyprinids) whose distribution and reproductive success may currently be constrained by temperature rather than by cold-adapted species (e.g. salmonids). Species that occur in Britain and Ireland that are at the edge of their distribution will be most affected, both negatively and positively. Populations of conservation importance (e.g.Salvelinus alpinus and Coregonus spp.) may decline irreversibly. However, changes in food-web dynamics and physiological adaptation, for example because of climate change, may obscure or alter predicted responses. The residual inertia in climate systems is such that even a complete cessation in emissions would still leave fishes exposed to continued climate change for at least half a century. Hence, regardless of the success or failure of programmes aimed at curbing climate change, major changes in fish communities can be expected over the next 50 years with a concomitant need to adapt management strategies accordingly.
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The MAGIC model of the responses of catchments to acidic deposition has been applied and tested extensively over a 15 year period at many sites and in many regions around the world. Overall, the model has proven to be robust, reliable and useful in a variety of scientific and managerial activities. Over the years, several refinements and additions to MAGIC have been proposed and/or implemented for particular applications. These adjustments to the model structure have all been included in a new version of the model (MAGIC7). The log aluminium ? pH relationship now does not have to be fixed to aluminium trihydroxide solubility. Buffering by organic acids using a triprotic analog is now included. Dynamics of nitrogen retention and loss in catchments can now be linked to soil nitrogen and carbon pools. Simulation of short-term episodic response by mixing fractions of different water types is also possible. This paper presents a review of the conceptual structure of MAGIC7 relating to long-term simulation of acidification and recovery, describes the conceptual basis of the new nitrogen dynamics and provides a comprehensive update of the equations, variables, parameters and inputs for the model. Keywords: process-based model, acid deposition, recovery
Article
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Acidification has caused the loss or reduction of numerous Atlantic salmon (Salmo salar L.) populations on both sides of the North Atlantic. Acid deposition peaked in the 1980's and resulted in both chronically and episodically acidified rivers. At present, water quality is improving in all affected rivers due to reduced acid deposition. However, spring snow melt, heavy rainfall and sea salt episodes can still cause short term drops in pH and elevated concentrations of bioavailable aluminum. Technical malfunction in lime dozers will cause short termed episodic spates in the limed rivers. The current situation has prompted a need for dose-response relationships based on short term exposures of Atlantic salmon to assess the potential population effects of episodic acidification. Water quality guidelines for salmon have been lacking, despite a large number of experiments, all demonstrating dose-response relationships between water chemistry and fish health. We have summarized results from 347 short-term (10 days) at an Al dose resulting in a gill Al concentration of up to 300 μg Alg−1 dw, a 3 day exposure resulting in a gill Al accumulation in the range of 25 to 60 μg Alg−1 dw reduces smolt to adult survival in a dose related manner by 20 to 50%. For smolt to adult survival, the biological significant response is delayed relative to the dose and occurs first after the fish enters the marine environment. In addition to exposure intensity and timing, exposure duration is important for the setting of critical limits.
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The acidification model MAGIC was used to predict recovery of small lakes in southernmost Norway to future reduction of acid deposition. A set of 60 small headwater lakes was sampled annually from either 1986 (35 lakes) or 1995 (25 lakes). Future acid deposition was assumed to follow implementation of current agreed legislation, including the Gothenburg protocol. Three scenarios of future N retention were used. Calibration of the sites to the observed time trends (1990–1999) as well as to one point in time considerably increased the robustness of the predictions. The modelled decline in SO<sub>4</sub><sup>*</sup> concentrations in the lakes over the period 1986–2001 matched the observed decline closely. This strongly suggests that soil processes such as SO<sub>4</sub> adsorption/desorption and S reduction/oxidation do not delay the response of runoff by more than a few years. The slope of time trends in ANC over the period of observations was less steep than that observed, perhaps because the entire soil column does not interact actively with the soilwater that emerges as runoff. The lakes showed widely differing time trends in NO<sub>3</sub> concentrations over the period 1986–2000. The observed trends were not simulated by any of the three N scenarios. A model based on the C/N ratio in soil was insufficient to account for N retention and leaching at these sites. The large differences in modelled NO<sub>3</sub>, however, produced only minor differences in ANC between the three scenarios. In the year 2050, the difference was only about 5 μeq l<sup>-1</sup>. Future climate change entailing warming and increased precipitation could also increase NO<sub>3</sub> loss to surface waters. SO<sub>4</sub><sup>*</sup> concentrations in the lakes were predicted to decrease in parallel with the future decreases in S deposition. Fully 80% of the expected decline to year 2025, however, had already occurred by the year 2000. Similarly, ANC concentrations were predicted to increase in the future, but again about 67% of the expected change has already occurred over the past 20 years. The recovery of ANC was predicted to be incomplete. Even after the CLE scenario (for future acid deposition) is implemented, the chemical conditions in about one-third of the lakes were predicted to be insufficient to support trout populations in the future. Thus, additional measures will be required if these lakes are to be restored. Keywords: acid deposition, lakes, model, Norway, recovery
Article
Water resources globally are affected by a complex mixture of stressors resulting from a range of drivers, including urban and agricultural land use, hydropower generation and climate change. Understanding how stressors interfere and impact upon ecological status and ecosystem services is essential for developing effective River Basin Management Plans and shaping future environmental policy. This paper details the nature of these problems for Europe's water resources and the need to find solutions at a range of spatial scales. In terms of the latter, we describe the aims and approaches of the EU-funded project MARS (Managing Aquatic ecosystems and water Resources under multiple Stress) and the conceptual and analytical framework that it is adopting to provide this knowledge, understanding and tools needed to address multiple stressors. MARS is operating at three scales: At the water body scale, the mechanistic understanding of stressor interactions and their impact upon water resources, ecological status and ecosystem services will be examined through multi-factorial experiments and the analysis of long time-series. At the river basin scale, modelling and empirical approaches will be adopted to characterise relationships between multiple stressors and ecological responses, functions, services and water resources. The effects of future land use and mitigation scenarios in 16 European river basins will be assessed. At the European scale, large-scale spatial analysis will be carried out to identify the relationships amongst stress intensity, ecological status and service provision, with a special focus on large transboundary rivers, lakes and fish. The project will support managers and policy makers in the practical implementation of the Water Framework Directive (WFD), of related legislation and of the Blueprint to Safeguard Europe's Water Resources by advising the 3rd River Basin Management Planning cycle, the revision of the WFD and by developing new tools for diagnosing and predicting multiple stressors.
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This report summarizes the findings and recommendations from the Expert Meeting on New Scenarios held in Noordwijkerhout, The Netherlands, 19-21 September 2007. It is the culmination of the combined efforts of the New Scenarios Steering Committee, an author team composed primarily of members of the research community, and numerous other meeting participants and external reviewers who provided extensive comments during the expert review process
Article
A model that explains 48% of the annual variation in Atlantic salmon Salmo salar smolt production in the River Orkla, Norway, has been established. This variation could be explained by egg deposition, minimum daily discharge during the previous winter and minimum weekly discharge during the summer 3 years before smolt migration. All coefficients in the model were positive, which indicates that more eggs and higher minimum discharge levels during the winter before smolt migration and the summer after hatching benefit smolt production. Hence, when the spawning target of the river is reached, the minimum levels of river discharge, in both winter and summer, are the main bottlenecks for the parr survival, and hence for smolt production. The River Orkla was developed for hydropower production in the early 1980s by the construction of four reservoirs upstream of the river stretch accessible to S. salar. Although no water has been removed from the catchment, the dynamics of water flow has been altered, mainly by increasing discharges during winter and reducing spring floods. In spite of the higher than natural winter discharges, minimum winter discharge is still a determinant of smolt production. Hence, in regulated rivers, the maintenance of discharges to ensure that they are as high as possible during dry periods is an important means of securing high S. salar smolt production.
Article
To improve understanding of natural and managed flow regimes in data-sparse regulated river systems in montane areas, the commonly used Hydrologiska Byråns Vattenbalansavdelning (HBV) conceptual run-off model was adapted to incorporate water regulation components. The extended model was then applied to the heavily regulated river Lyon (391 km2) in Scotland to reconstruct the natural flow regime and to assess the impacts of regulation at increasing spatial scales. Multi-criteria model evaluation demonstrated that the model performed well in capturing the dominant catchment processes and regulation effects, especially at the timescales at which operation rules apply. The main change as a result of regulation in the river Lyon is a decrease in inter-annual and intra-annual variability of all elements of the flow regime, in terms of magnitude, frequency, and duration. Although these impacts are most pronounced directly downstream of the impoundments, the regulation effects propagate throughout the river system. The modelling approach is flexible and widely applicable and only limited amounts of data are required. Moreover, results are easily communicated to stakeholders. It has the potential to contribute to the development of flow regimes that may be more beneficial to the ecological status of rivers. In the case of the river Lyon, it is likely that this involves a more variable release regime. The approach developed here provides a tool for assessing impacts on flow regimes and informing environmental flows in other data-sparse regions with heavily regulated montane river systems. Copyright © 2014 John Wiley & Sons, Ltd.
Article
Relatively little is known about the downstream migration of landlocked stocks of Atlantic salmon Salmo salar L. smolts, as earlier migration studies have generally focused on upstream migration. However, in watersheds with many hydroelectric plants (HEPs), multiplicative loss of downstream-migrating salmon smolts can be high, contributing to population declines or extirpations. Here we report the results from a study of wild landlocked Atlantic salmon smolts in the River Klarälven. Salmon smolts, tagged with acoustic transmitters, were released at different locations and followed as they passed 37 receivers along a 180-km-long river segment, including eight dams as well as free-flowing control stretches. We found that 16% of the smolts successfully migrated along the entire river segment. Most losses occurred during HEP passages, with 76% of the smolts being lost during these passages, which contrasts with the 8% smolt loss along unregulated control stretches. Migration speed was 83% slower along regulated stretches than along unregulated stretches. The observed lower migration speed at regulated stretches was dependent on fish size, with large fish moving slower than small fish. Discharge affected migration speed but not losses. As previously shown for anadromous populations, our study of landlocked salmon demonstrates similar negative effects of multiple passages of HEPs by downstream-migrating smolts. On the basis of this and previous migration studies, we advocate using a holistic approach in the management and conservation of migratory fish in regulated rivers, which includes safe passage for both upstream- and downstream-migrating fish. Copyright © 2012 John Wiley & Sons, Ltd.
Article
Research in recent years has led to conceptualizations of the long-term responses of catchment surface water quality to acidic deposition. That research has focused attention on certain soil processes as likely keys to catchment responses (anion retention, cation exchange, primary mineral weathering, aluminum dissolution, and CO2 solubility). We present a mathematical model which uses quantitative descriptions of these soil chemical processes to estimate the long-term chemical changes that occur in the soil, soil water, and surface waters of catchments in response to changes in atmospheric deposition. The model is applied to a small forested catchment in the Shenandoah National Park, Virginia. Historical changes in surface water quality are reconstructed for the catchment for the last 140 years. The model indicates that alkalinity of surface waters in the catchment may have been reduced by as much as 50%. Water quality is forecast for the catchment under three different scenarios of future changes in atmospheric deposition. The model indicates that all but very large reductions in deposition will result in further deterioration of the catchment water quality. The process-oriented, lumped-parameter approach used is consistent with all currently available observations of water quality in the catchment. Due to the lack of long-term records of catchment water quality, strict verification of the model estimates and an assessment of the model validity is problematic. This is the case for all models of long-terrn catchment chemical responses to acid deposition. Nonetheless, the model provides a means of integrating the results of individual process level laboratory and field studies. Used this way, the model becomes a vehicle for examining the interactions and long-term implications of our conceptualization of the acidification process.
Article
This review attempts to assess, as quantitatively as possible, the habitat requirements in fresh water of three common and widespread European salmonid species. Namely: the trout (Salmo trutta L.), the salmon (S. salar L.) and the grayling (Thymallus thymallus L.). Requirements are considered for spawning, incubation and emergence, juveniles and smolts and for adults and spawning movements.
Article
Despite its status as a flagship species, wild Atlantic salmon ( Salmo salar) has been in decline in most of Europe for the last three to four decades. Better catch records during this period, and increasing numbers of escaped farm salmon, suggest that the actual decline in wild salmon has been stronger than that estimated from catches. The decline has been particularly strong in some rivers producing high proportions of late-maturing salmon. The causes for the decline are manifold and include both natural environmental variation and man-made changes. Among the former, marine conditions are believed to have been unfavourable for both growth and survival of salmon since the early 1980s. Among the latter, negative effects associated with the build-up of salmon farming, such as the spread of diseases and escape of farm fish, are believed to be major contributors, together with the more "traditional" causes like pollution and watercourse regulation. Moreover, by-catches of salmon at sea may contribute to the decline of some populations. There are, however, some positive trends, in particular in rivers previously affected by local or long-transported pollution. The future of wild Atlantic salmon seems to depend on better inter- departmental co-operation in recognizing and controlling the man-made factors affecting wild populations, and on research which improves our understanding of the regulating factors in salmon populations. A major challenge lies in developing salmon farming into a sustainable industry.
Article
By comparing long-term changes in the crustacean zooplankton communities of three experimentally limed lakes near the Sudbury, Ontario, metal smelters with both temporal and spatial reference lakes distant from Sudbury, we (i) demonstrate the value of reference lakes for studies of recovery, (ii) compare univariate versus' multivariate indicators of recovery, and (iii) determine if the pace of recovery was regulated by the severity of acid and metal contamination. The reference lakes provide recovery targets and norms of interannual variability. As indicators of damage and recovery, the performance of the univariate metrics was richness = diversity > evenness > abundance. Multivariate metrics were developed by projecting the Sudbury data onto a correspondence analysis of the spatial reference data. Univariate and multivariate approaches were equally sensitive for metrics based on species presence; however, the multivariate metrics incorporating the relative abundances of taxa were the best overall performers. While the two more acidic (pH 4.5) lakes had not recovered 15 years after neutralization, the zooplankton of Nelson Lake, the least acidic (pH 5.7) of the experimental lakes, recovered completely within 10 years of liming. This augurs well for the recovery of zooplankton in thousands of moderately acidic North American lakes, should international reductions in SO2 emissions reverse their acidification.
Article
Moderately acidified Lake Njupfatet was studied during 2 consecutive years, before and after liming (calcite), and compared with corresponding data from six reference lakes. After liming, the concentration of total phosphorus in the lake water decreased by some 30% as did the concentrations of particulate carbon, particulate nitrogen, particulate phosphorus, and phytoplankton biomass. Because of significant increases of inorganic nitrogen and dissolved organic carbon, the concentrations of total nitrogen and total organic carbon remained unchanged after liming. Before liming, there was a close balance between phosphorus and nitrogen limitation of phytoplankton growth, but we conclude that after liming the reduced concentrations of phosphorus induced phosphorus limitation of phytoplankton growth. Liming changed the phytoplankton community structure, most importantly causing the complete loss of the dominant species before liming, the cyanophyte Merismopedia tenuissima. The decrease in total biomass of phytoplankton was not compensated for by a corresponding increase in other species. After liming total biomasses of bacterioplankton and protozoan zooplankton did not change, while total biomass of metazoan zooplankton increased; hence, total plankton community carbon remained unchanged. Phytoplankton, protozoan, and metazoan zooplankton diversity (Shannon index) did not change after liming. Zooplankton biomass remained heavily dominated by calanoid copepods, typical of acidified lakes.
Article
Atlantic salmon (Salmo salar) is one of the most extensively studied fish species in the world due to its significance in aquaculture, fisheries and ongoing conservation efforts to protect declining populations. Yet, limited genomic resources have hampered our understanding of genetic architecture in the species and the genetic basis of adaptation to the wide range of natural and artificial environments it occupies. In this study, we describe the development of a medium-density Atlantic salmon single nucleotide polymorphism (SNP) array based on expressed sequence tags (ESTs) and genomic sequencing. The array was used in the most extensive assessment of population genetic structure performed to date in this species. A total of 6176 informative SNPs were successfully genotyped in 38 anadromous and freshwater wild populations distributed across the species natural range. Principal component analysis clearly differentiated European and North American populations, and within Europe, three major regional genetic groups were identified for the first time in a single analysis. We assessed the potential for the array to disentangle neutral and putative adaptive divergence of SNP allele frequencies across populations and among regional groups. In Europe, secondary contact zones were identified between major clusters where endogenous and exogenous barriers could be associated, rendering the interpretation of environmental influence on potentially adaptive divergence equivocal. A small number of markers highly divergent in allele frequencies (outliers) were observed between (multiple) freshwater and anadromous populations, between northern and southern latitudes, and when comparing Baltic populations to all others. We also discuss the potential future applications of the SNP array for conservation, management and aquaculture.
Article
The river Surna has been regulated for hydropower production since the late 1960s, with a minimum flow requirement of ca. 30% of the mean annual flow downstream of the power plant outlet, leaving a large by-pass section with residual flow. This river has recently been selected as a national salmon watercourse by the Norwegian Parliament. Mitigations to protect the Atlantic salmon stock will be given priority in these rivers, and hence an environmental flow assessment (EFA) has been started to optimize hydropower production in relation to salmon habitat. A suite of methodologies for EFA like habitat-hydraulic models, indicators of hydrological alteration (IHA), mesohabitat analysis, temperature simulations and optimalization of habitat improvements, has been applied across scales and seasons in this catchment. The EFA has been related to various hydropower schemes, to suggest more salmon-friendly hydropower operation. A temperature-adjusted running of the hydropower plant was found to have a major influence on the production of salmonids. Downstream of the hydropower station, rapid ramping has often occurred. This is possibly harmful for juvenile fish inhabiting the shallow parts of the river due to stranding. Based on our habitat modelling toolkit, we have suggested ramping guidelines to drastically reduce stranding of juvenile salmonids. Our EFA has indicated a great potential with mitigations to increase salmon production in the river Surna. For maximum gain, combinations of more gentle flow ramping, habitat improvements and/or environmental flow requirement (EFR) in the by-pass section and temperature alteration by new intake arrangements and/or temperature-adjusted run of the power plant are needed. Copyright © 2007 John Wiley & Sons, Ltd.
Article
Gas bubble disease (GBD) has been recognized as a potential problem for fishes in the Columbia River basin. GBD results from exposure to gas supersaturated water created by discharge over dam spillways. Spill creates a downstream plume of water with high total dissolved gas supersaturation (TDGS) that may be positioned along either shore or mid-channel, depending on dam operations. We obtained spatial data on fish migration paths and migration depths for adult spring and summer Chinook salmon, Oncorhynchus tshawytscha, during 2000. Migration paths were compared to output from a two-dimensional (2-dimensional) hydrodynamic and dissolved gas model to estimate the potential for GBD expression and to test for behavioural avoidance of the high TDGS plume. We observed salmon swam sufficiently deep in the water column to receive complete hydrostatic compensation 95.9% of the time spent in the Bonneville Dam tailrace and 88.1% of the time in the Ice Harbor Dam tailrace. The majority of depth uncompensated exposure occurred at TDGS levels > 115%. Adult Chinook salmon tended to migrate near the shoreline and they tended to remain in relatively deep water. Adults moved into the high dissolved-gas plume as often as they moved out of it downstream of Bonneville Dam, providing no evidence that adults moved laterally to avoid areas with elevated dissolved gas levels. When water depths decreased due to reduced river discharge, adults tended to migrate in the deeper navigation channel downstream from Ice Harbor Dam. The strong influence of dam operations on the position of the high-TDGS plume and shoreline-orientation behaviours of adults suggest that exposure of adult salmonids to high-TDGS conditions may be minimized using operational conditions that direct the spilled water mid-channel. Our approach illustrates the potential for combined field and modelling efforts to estimate the fine-scale environmental conditions encountered by fishes in natural and regulated rivers.
Article
Acidification is one of the most serious environmental problems in Norway. International agreements to reduce emissions are the only acceptable solution to the acidification problem. The Sulphur Protocol, signed in Oslo in 1994, will certainly improve matters, but southern Norway will have large acidified areas for decades. Norwegian environmental authorities therefore carry out liming as a temporary alleviatory measure to reduce damage for freshwater ecosystems. In 1995, about NOK 92 mill, was spent on liming. Acidification has wiped out the salmon in 25 rivers, and they are threatened in another 28 rivers. Because of varying water flow and rapidly changing water quality, liming a Norwegian salmon river is a huge operation demanding sophisticated equipment. Eleven rivers carrying anadromous fish are being limed in 1995. The largest is the River Audna where liming has meant that a salmon stock could be reintroduced. Most rivers are limed using automatic lime dosers. The most sophisticated ones control the amount of lime using pH sensors and water flow to neutralize major episodes of acidic water flow, which regularly occur in Norwegian rivers.
Article
The MAGIC model was used to evaluate the relative sensitivity of several possible climate-induced effects on the recovery of soil and surface water from acidification. A common protocol was used at 14 intensively studied sites in Europe and eastern North America. The results show that several of the factors are of only minor importance (increase in pCO(2) in soil air and runoff, for example), several are important at only a few sites (seasalts at near-coastal sites, for example) and several are important at nearly all sites (increased concentrations of organic acids in soil solution and runoff, for example). In addition changes in forest growth and decomposition of soil organic matter are important at forested sites and sites at risk of nitrogen saturation. The trials suggest that in future modelling of recovery from acidification should take into account possible concurrent climate changes and focus specially on the climate-induced changes in organic acids and nitrogen retention.
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Prognoses for Future Acidification Recovery of Water, Soils and Forests: Dynamic Modeling of Norwegian Data from ICP Forests. ICP IM and ICP Waters
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Larssen, T., Clarke, N., Tørseth, K., Skjelkvåle, B.L., 2002. Prognoses for Future Acidification Recovery of Water, Soils and Forests: Dynamic Modeling of Norwegian Data from ICP Forests. ICP IM and ICP Waters. Norwegian Institute for Water Research, Oslo, p. 38.
Bleka in Byglandsfjord – population status and measures to increase recruitment
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  • B O Martinsen
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  • T Wiers
Barlaup, B.T., Sandven, O.R., Skoglund, H., Kleiven, E., Kile, N.B., Vethe, A., Martinsen, B.O., Garbielsen, S.E., Wiers, T., 2009. Bleka in Byglandsfjord – population status and measures to increase recruitment 1999–2008. DN-utredning 5-2009. Directorate for Nature Management, Trondheim, Norway (In Norwegian), pp. 1–88.
Salmon and water quality in the Otra River
  • F Kroglund
  • R Høgberget
  • K Hindar
  • G Østborg
  • T Balstad
Kroglund, F., Høgberget, R., Hindar, K., Østborg, G., Balstad, T., 2008a. Salmon and water quality in the Otra River, 1990-2006. NIVA Report 5531-2008. Norwegian Institute for Water Research, Oslo, Norway.
Liming of acidified lakes and rivers in Norway -an attempt to preserve and restore biological diversity in the acidified regions
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Sandoy, S., Romundstad, A.J., 1995. Liming of acidified lakes and rivers in Norway -an attempt to preserve and restore biological diversity in the acidified regions. Water Air Soil Pollut. 85, 997-1002.
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Management Plan for Water Region Southwest. Water district Otra and Figgjo
  • F Vest-Adger
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Hydropower development -ecological effects
  • B O Johnsen
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  • B T Barlaup
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Impacts of air pollution on freshwater acidification under future Emission reduction scenarios; ICP waters contribution to WGE report
  • R F Wright
  • R Helliwell
  • J Hruska
  • T Larssen
  • M Rogora
  • D Rzychoń
  • B L Skjelkvåle
  • A Worsztynowicz
Wright, R.F., Helliwell, R., Hruska, J., Larssen, T., Rogora, M., Rzychoń, D., Skjelkvåle, B.L., Worsztynowicz, A., 2011. Impacts of air pollution on freshwater acidification under future Emission reduction scenarios; ICP waters contribution to WGE report. NIVAreport 6243-2011. Norwegian Institute for Water Research, Oslo, Norway.
Overvåking av langtransportert forurenset luft og nedbør. Atmosfaeriske tilførsler 2012.Statlig program for forurensningsovervåking Norwegian Institute for Air Research
  • W Aas
  • S Solberg
  • S Manø
  • K E Yttri
Aas, W., Solberg, S., Manø, S., Yttri, K.E., 2013. Overvåking av langtransportert forurenset luft og nedbør. Atmosfaeriske tilførsler 2012.Statlig program for forurensningsovervåking. Rapport 1148/2013. M-3/2013.(14/2013). Norwegian Institute for Air Research, Kjeller, Norway (in Norwegian).