Sigurd Rognerud

Heavy metal pollution in sediments of the Pasvik River drainage

The purpose of this paper is to study the regional impacts of heavy metals (Ni, Cu, Co, Zn, Cd, Pb, Hg) on the watershed of the Pasvik River. On the basis of sediment investigations at 27 stations of the watershed, background concentrations of the heavy metals, vertical distribution of heavy metals in sediments, heavy metal concentrations in surface sediments, contamination degree, and risk index were determined. The atmospheric emissions of Ni, Cu, Co, Zn, Cd and Hg from the smelters and waste waters from tailing dams and mines of the Pechenganickel Company are likely to be the main sources of increasing concentrations observed in recent sediments of the lower river reaches. Lead showed a different pattern from the other heavy metals--increasing Pb concentrations in the upper sediment layers towards the Norwegian side.

Trace Element Contamination of Norwegian Lake Sediments

Abstract Concentrations of Sb, Hg, Bi, Cd, Mo, As, Co, Ni, Cr, Cu, V, Pb and Zn in surface and preindustrial sediments from 210 lakes in Norway were used for studying modern atmospheric depositions of these elements. Surface sediments had considerably higher concentrations of Sb, Hg, Bi, Cd, As, Pb than preindustrial sediments. The differences decreased with latitude and altitude. A multivariate analysis including the trace elements and the major constituents (organic matter, Si, Al, Fe and Mn) of surface sediments suggested the following relationships: Sb, Hg, Bi, As, and Pb formed a group with strong associations to organic matter. Ni, Cr and Cu formed a second group, weakly associated to the inorganic sediment fraction (Si and Al). Zn and Cd formed a third group with weak associations to organic matter. Co was associated to Mn, whereas Mo and V showed no important covariations with any other trace elements or major components.

Environmental factors influencing mercury speciation in Subarctic and Boreal lakes

Environmental drivers of total mercury (TotHg) concentrations, methylmercury (MeHg) concentrations, and MeHg fractions (a proxy for methylation potential, expressed as %MeHg) were assessed in a synoptic study of 51 lakes in southeast (Boreal) and northeast (Subarctic) Norway. Concentrations of TotHg and MeHg ranged between 0.5-6.6 ng/L and <0.02-0.70 ng/L, respectively. The lakes span wide ranges of explanatory environmental variables, including water chemistry, catchment characteristics, climate conditions, and atmospheric deposition of Hg, sulphur and nitrogen (N). Dissolved organic matter (DOM), measured as total organic carbon (TOC), was the variable most strongly correlated with TotHg (r(2)=0.76) and MeHg (r(2)=0.64) concentrations. Lakes in the Subarctic region had significantly lower TotHg and MeHg concentrations, and %MeHg than lakes in the Boreal region (p<0.01), implying a lower aquatic food web exposure of aqueous Hg species in Subarctic Norway than in the Boreal lakes. Statistical modelling (partial least squares) using data from the Boreal lakes produced models explaining 82%, 75% and 50% of the spatial variation of TotHg and MeHg concentrations and %MeHg, respectively. After TOC, the most significant explanatory variables were N availability, base cation status, and lake and catchment size. We conclude that a key process driving TotHg concentrations is DOM as a transport vector, while the role of DOM for MeHg and %MeHg is likely related to a combination of transport and DOM as a substrate for methylation. Also, negative correlations between MeHg, and catchment and lake size are consistent with in-lake and in-stream de-methylation processes. The statistical relationship suggests that N availability exerts a positive contribution on concentrations of MeHg and %MeHg.

Habitat use and diet of sympatric Arctic charr (Salvelinus alpinus) and whitefish (Coregonus lavaretus) in five lakes in southern Norway: not only interspecific population dominance?

Stable coexistence of Arctic charr and whitefish does occur in a number of native lake fish communities in Scandinavia. Even so, whitefish introductions into Arctic charr lakes have resulted in serious decline and possibly local extinction of Arctic charr. In this article, we analyze the habitat use and diet of the two species in five Norwegian lakes differing in basin shape and environmental conditions. In two of the lakes, both species are native, and appear to live in a relatively stable coexistence. Here, whitefish mainly occupy the littoral and upper pelagic zone, while Arctic charr live in the deeper habitats. Diets are generally quite different in terms of the zooplankton species eaten. In the three other lakes, either whitefish or both species have been introduced. In the shallowest lake, habitat segregation is similar to that seen in the pristine lakes, although Arctic charr appears to be on the brink of extinction. In the remaining two lakes, however, Arctic charr dominates, and occurs in higher numbers than whitefish in all the habitats. Our observations indicate that coexistence of the two species in oligotrophic and relatively pristine lakes requires an extensive profundal zone to serve as a refugium for Arctic charr. If the littoral zone is rendered inaccessible or unprofitable for whitefish due to dominance of a third competitor or predator, or as a result of lake regulation, then Arctic charr may be the dominant species.

Levels of persistent organic pollutants in the Neretva River (Bosnia and Herzegovina) determined by deployment of semipermeable membrane devices (SPMD).

The main objective of this study was to determine levels of certain persistent organic pollutants (POPs) in Neretva River, Bosnia and Herzegovina (BiH), which is currently facing implementation of the Stockholm Convention on persistent organic pollutants (POPs) and environmental protection strategies. This is the very first report on the deployment of semipermeable membrane devices (SPMDs) in BiH. SPMDs were used for continuous 3-weeks sampling of POPs at three locations, covering 220 km long stream of the Neretva River. Water concentrations of polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides (OCPs) and polybrominated diphenylethers (PBDEs) were calculated using performance reference compounds (PRCs). The total OCP concentrations ranged from 40 to 140 pg L−1 and most of compounds were detected only in lower course of the river. Total PAH ranged from 160 to 4000 pg L−1 and show a clear spatial variation. Dominant PAHs were phenanthrene, fluoranthene, fluorene and acenaphthene. Total PCB ranged from undetectable to 120 pg L−1. From the group of 15 PBDE congeners investigated, only PBDE-47 and PBDE-99 were detected. Since the concentrations of broad spectrum of POPs found in the Neretva River are quite low, future actions should be focused on preservation rather than on sanitation measures. Regular monitoring should anyhow be established.

Seasonal and year‐to‐year variation of mercury concentration in perch (Perca fluviatilis) in boreal lakes

The authors examined the seasonal and year-to-year variations of mercury (Hg) concentrations in populations of perch (Perca fluviatilis) from 2 boreal freshwater lakes in southeast Norway. Fish Hg concentrations were determined seasonally (spring, summer, and autumn) over 3 yr (2010, 2011, and 2012) to test the hypothesis that there are substantial changes in fish Hg concentrations during the year (seasonal variation) as well as annually. Concentrations were significantly (p < 0.0001) different in the 2 study lakes, with mean seasonal concentrations varying from 0.24 mg/kg to 0.36 mg/kg and from 0.29 mg/kg to 0.37 mg/kg, respectively. The Hg concentrations of both perch populations showed significant year-to-year (p < 0.0001) and seasonal variation (p < 0.01). The changing fish Hg concentrations were 25% and 28% (2010-2011) and 17% and 0% (2011-2012) in the 2 lakes over the 3 yr, respectively. The results demonstrate how the significant year-to-year increase is, among other variables, related to changes in trophic position, shown through stable nitrogen (δ(15)N) isotope data. The seasonal variation is related to summer growth dilution. The results highlight the clear need for yearly studies of fish Hg concentrations, rather than the 3-yr cycle suggested by current European policy through the Water Framework Directive. The lack of yearly sampling may result in erroneous conclusions regarding fish Hg concentration time trends.

The trophic niche of Arctic charr in large southern Scandinavian lakes is determined by fish community and lake morphometry

Abstract The influence of interspecific interactions and habitat characteristics on the ecological niche of species’ populations is a controversial issue in ecology. We explored the niche use of Arctic charr (Salvelinus alpinus L.) in seven relatively large and deep lakes in southern Norway. We aimed to investigate how the presence of potentially competitive fish species, such as whitefish (Coregonus lavaretus L.), perch (Perca fluviatilis L.) and brown trout (Salmo trutta L.), and the lake morphometry affects the littoral reliance and niche breadth of Arctic charr. Stable isotope (δ13C and δ15N) analyses showed that Arctic charr relied less on littoral food resources than brown trout and perch but had largely overlapping niche with whitefish. Arctic charr showed narrower niche use (i.e. less individual variation in δ13C and δ15N) than the other fish species in all seven lakes, particularly in communities where both littoral and pelagic competitors were present. Our results demonstrate that Arctic charr rely much less on littoral resources (<50%) in large and deep lakes in southern Scandinavia than in small, shallower subarctic lakes, and that interspecific interactions with both littoral and pelagic resource competitors can lead to niche compression of this generalist salmonid fish.

Introduced European smelt (Osmerus eperlanus) affects food web and fish community in a large Norwegian lake

Invasive and introduced fishes can affect recipient ecosystems and native species via altered competitive and predatory interactions, potentially leading to top-down and bottom-up cascading impacts. Here, we describe a case from a large lake in southern Norway, Storsjøen, where the illegal introduction of a small, predominantly planktivorous fish species, European smelt (Osmerus eperlanus), has led to changes in the native fish community and lake food web. Survey fishing data collected before (2007) and after (2016) the introduction indicates that smelt has become the numerically dominant fish species both in benthic and pelagic habitats, with concurrent reductions in the relative abundance of native European whitefish (Coregonus lavaretus) and Arctic charr (Salvelinus alpinus) populations. Stable isotope (δ13C and δ15N) data indicate minor changes in the trophic niches of native whitefish and Arctic charr despite partly overlapping niches with the introduced smelt. In contrast, brown trout (Salmo trutta) showed an earlier shift to piscivory, a more pelagic niche and increased growth rate, likely because of the smelt induced increase in pelagic prey fish abundance. The main trophic pathway supporting top predators (i.e., large brown trout) in Storsjøen has, therefore, shifted from a littoral to a more pelagic base. Our study demonstrates that small-sized introduced fishes can alter lake food-web dynamics, with contrasting impacts on native fishes. This knowledge is vital for future evaluation and mitigation of potential impacts of smelt introductions on lake ecosystems.