Lakes In Norway Research Articles

The relative importance of acidity sources for humic lakes in Norway

The possible role of natural processes contributing to lake acidification and the occurrence of acidic lakes pH<5) has received considerable attention1–7, but there has been no direct test of the importance of some of the postulated natural processes in Scandinavia where large numbers of acidic lakes occur. Some authors have argued that lakes were acidic simply because of processes occurring in acid soils, and that the effects of acidic precipitation on these lakes were thereby overestimated1,2. We present here an analysis of the role of strong and weak acids in the acidity status of moderately humic lakes (total organic carbon (TOC) 2–15 mg 1−1) in two areas of Norway. The two areas received precipitation with differing acidity and amounts of sulphate. Our data suggest contributions by organic acids to acidity, but strong acids associated with sulphate further reduce the pH and explain the recent acidification of coloured lakes in southern Norway.

Multiattribute analysis of the impact on society of phosphorus abatement measures

We have constructed a decision goal hierarchy evaluating the impact and cost to society of phosphorus abatement measures to improve lake water quality. We examine three primary measures: sewage treatment, ban of detergents containing phosphorus, and changes in agricultural practice, and combinations of these measures. The water system studied is lakes in Norway represented by eight typical water bodies. The results showed that the highest utility was obtained by “status quo” (0.90 ± 0.02) and implementing measures in agriculture (0.90 ± 0.02). The combined measures including sewage treatment and ban on phosphorus containing detergents scored lowest (0.73 ± 0.08).

Freshly prepared rat hepatocytes used in screening the toxicity of blue-green algal blooms.

The acute toxicity of extracts of blue-green algae was tested in freshly prepared rat hepatocytes in suspension. The results were compared with the traditional in vivo mouse bioassay. Sixty samples of natural algal blooms from freshwater lakes in Norway, Sweden, and Finland and 14 samples cultured in the laboratory were tested. The mouse bioassay revealed hepatotoxins in a large number of the algae, while neurotoxins were not found. Acute hepatotoxicity in vitro was scored by measurement of leakage of the enzyme lactate dehydrogenase (LDH) from damaged cells and of morphological changes of the cells. The correlation coefficients between mouse toxicity and LDH, mouse toxicity and morphological cell damage, and between LDH and morphological cell damage were 0.812, 0.735, and 0.882, respectively. Consequently, the rat hepatocyte toxicity test seems to be well suited for screening blooms of blue-green algae for the presence of hepatotoxins.

The Rehabilitation of Norway's Largest Lake

Lake Mjøsa, situated in the southeast of Norway, is the largest lake in Norway. Originally it was an oligotrophic lake, rich in oxygen down to its deepest part, 449 m below the surface and 328 m below sea level. In the period after 1950 signs of eutrophication developed reaching a maximum in the mid-1970's with the mass occurrence of filamentous blue-green algae. Comprehensive investigations have yielded data on the physical, chemical and biological characteristics of the lake. The trophic state is well described by the Vollenweider model. A phosphorus control program was suggested and made possible through Government funds. The Ministry of Environment organized a campaign which began in 1977 and which already seems to give the results expected.

The Chemistry and Fishery Status of Acid Lakes in Norway and Their Relationship to European Sulphur Emissions

(1) In the light of claims that some Scandinavian lakes have been adversely affected by European sulphur emissions, the data of Wright & Snekvik (1978) have been analysed in an attempt to estimate the effect of a reduction in these emissions on the fishery status of the lakes. (2) The relationship of hydrogen-ion concentration and excess (non-sea) sulphate concentration is highly significant, but the slope of regression is only 0-225. (3) On the assumptions that the excess sulphate is largely derived from the combustion of fossil fuels, and that a regression derived from a regional survey can be used to predict trends in time, the average increase in pH of these lakes that might result from a 50% reduction in European sulphur emissions would be 0.2 units. This figure is not inconsistent with estimates made from other studies, including analysis of historical data, sediment analysis and experimental catchment acidification. (4) The relationship between pH and fishery status of the lakes, in terms of their ability to support good, sparse, or no fish populations, suggests that a pH change of 0.2 units would improve the fishery status category of 9% of the lakes. (5) Fishery status of these lakes appears to be independent of excess sulphate concentration.

Seasonal dynamics in abundance, development and pattern of infection of Bunodera luciopercae (Müller) in perch, Perca fluviatilis L. from an oligotrophic lake in Norway

Samples of perch, Perca fluviatilis L., were examined monthly for the presence of the intestinal trematode Bunodera luciopercae (Müller). Marked seasonal cycles in incidence and intensity of infection were found, with a minimum level in July, when all the fish examined were free of the fluke, and a maximum level in February. Five developmental stages of the fluke were recognized and the seasonal changes in the percentage distribution of these stages were studied. Infective larvae were found in the period August–March, with a peak in January. Gravid worms were mainly found in the period May‐June. The frequency distribution of parasite counts were over‐dispersed and followed the negative binomial distribution within fish samples from different periods of the year.

Population biology of the nematode Camallanus lacustris in perch, Perca fluviatilis L., from an oligotrophic lake in Norway

Samples of perch, Perca fluviatilis, were examined for the contents of their gastrointestinal tract and for the intestinal nematode Camallanus lacustris (Zoega). The seasonal dynamics, dispersal pattern and site preference of the nematode were studied. Both larvae and adult worms were present in the perch throughout the year. The abundance of C. lacustris was non‐seasonal, but seasonal cycles were found in the numbers of larvae and of gravid females. C. lacustris showed a tendency to an increase in mean intensity with the size of perch. The frequency distribution of the nematode followed the negative binomial at different times of the year and in different length groups of perch. C. lacustris showed a seasonal site preference in the perch gut.

Life history and growth of Asellus aquaticus (L.) in relation to environment in a eutrophic lake in Norway

A new life history pattern for Asellus aquaticus is described from Lake Ostensjovatn in Oslo. Overwintering specimens (generation A) breed in spring. The next generation B matures, breeds and dies in first summer, giving rise to the overwintering generation C, which breeds next spring and dies. The death of generation B in its first summer could be shown by a study of oostegit development in the females. The end of the breeding season in autumn is thus accomplished by a complete replacement of generations. This pattern can be a) light stimulated, or b) a pre-determined cycle, uninfluenced by environmental factors. Breeding starts in spring when water temperature reaches about 7–8°C. Estimated incubation time was 23–35 days, corresponding to about 300 degree-days above 4°C. No growth took place from November till March–April. Growth started when water temperature reached 3–5°C. Growth increments per degree-day above 3°C were the same for the three generations which were followed, in spite of their different life spans and different temperatures. The total number of degree-days above 3°C available to the generations seemed to regulate the maximum length of the specimens in the respective generations. Comparison with life histories of the species in other lakes suggests that the different patterns described reflect an evolutionary adaptation to major environmental factors.

Concentrations of heavy metals in small Norwegian lakes

As part of regional surveys of lakes in Norway the concentrations of Zn, Pb, Cu and Cd were measured in surface- and bottom-water samples collected from representative, small, pristine lakes (136 in southern Norway sampled in October 1974, 58 resampled in March 1975, and 77 in northern Norway sampled in March 1975). The lakes, a statistically representative sample of small lakes in Norway, were chosen such that their watersheds are undisturbed. Heavy-metal concentrations in these lakes thus reflect only natural inputs and anthropogenic inputs via the atmosphere. The generally low concentrations (Zn 0.5–12.0 μg l −1; Pb 0–2.0 μg l −1; Cu 0–2.0 μg l −1; Cd 0.1-0.5 μg l −1) measured in lakes in central and northern Norway provide estimates of natural “background” levels. These estimates may be too high because they include the global-scale deposition of heavy metals from the atmosphere which has increased as a result of industrial activities. Concentrations of Zn and Pb in lakes in southernmost and southeastern Norway lie above these “background” levels, apparently because of atmospheric deposition associated with the acidic precipitation that falls over southern Scandinavia. Increased heavy-metal concentrations in acid lakes may also be due to increased mobilization of metals due to acidification of soil- and surface-waters.

Studies on eutrophication of some Norwegian inland waters

SummaryMost rivers and lakes in Norway have a water of oligotrophic nature. The use of land in the catchment areas for agriculture and human settlement leads to an enrichment of the water. Phytoplankton investigations during the last five years have demonstrated recent changes in the trophic nature of several inland waters. Species of Oscillatoria have previously in a few cases only been reported as the cause of algal blooms. At least four oscillatorians are now common in such developments of plankton vegetation. They are: Oscillatoria Agardhii var. isothrix Skuja, Oscillatoria sp., Oscillatoria cf. rubescens D. C. and Oscillatoria Agardhii Gom. (fig. 2, 3, 4, 5 and 6).The three lakes L. Steinsfjord, L. Gjersjøen and L. Årungen (fig. 1) cover a range from a low grade of eutrophy to extreme eutrophy. Data about the lakes are listed in table 1, and an example of their hydrography at the end of summer stagnation are given in fig. 7. The vegetation of blue green algae and the state of eutrophication of the lakes are discussed.Laboratory cultures of algae have been used to demonstrate the effects of fertilization by domestic sewage on recipient water. The experimental procedure used is briefly described. Results from a regional survey where algal cultures were used to express changing growth qualities of the water flowing down a drainage basin are presented (fig. 8). An experiment is described where the results obtained (fig. 9) indicated that the qualities of the recipient water may be as important for the effect of pollution with respect to consequences for algal growth, as the amount and composition of the sewage itself.

Search for isostatically trapped sea water in New Zealand

Abstract A few lakes in Norway and British Columbia with sills not far above present sea level contain salt bottom water that is thought to be trapped sea water (Table 1). The lakes are considered to have once been arms of the sea (fiords) and the sills to have been raised above sea level at the end of the Last Glaciation by isostatic uplift caused by melting of a thick and extensive ice cover.

Observations on the Drainage of a Glacier-Dammed Lake in Norway

AbstractThe behaviour of a Norwegian glacier-dammed lake, before, during and after drainage in 1957 is described. The evidence of former shoreline terraces is interpreted and possible drainage mechanisms are discussed.

Observations on the Drainage of a Glacier-Dammed Lake in Norway

Abstract The behaviour of a Norwegian glacier-dammed lake, before, during and after drainage in 1957 is described. The evidence of former shoreline terraces is interpreted and possible drainage mechanisms are discussed.

Glacier Dammed Lakes in Norway

Glacier dammed lakes may have their outflow over a bedrock threshold like other lakes, or they may flow on the surface or below the damming ice. In the former case the lake, over some considerable period, has a constant maximum level with marked shore lines corresponding to the threshold. But when the level is determined by the ice dam, the conditions are unstable. The level of the lake will then to a certain extent vary in step with the glacier, and never remain at a certain level for any length of time. The normal behaviour of such a lake will be a moderately fast rise of the water level, dependent upon the supply, until a certain critical level is reached, whereupon drainage is rapid. Such is also to some extent the case with the type of lake first mentioned, if the height of the pass is situated near to the critical level for drainage.

Seismic seiches in Norway and England during the Assam earthquake of August 15, 1950*

Abstract During the Assam earthquake of August 15, 1950, unusual waves were observed in at least 37 localities in fjords and lakes in Norway. Reports from 29 of these are discussed in this paper. In most places the waves were standing waves, with periods of 1 to 3 minutes and amplitudes of 5 to 100 cm. and began when the acceleration at the seismological observatory in Bergen surpassed 20 milligals in the east-west direction and 40 milligals in the vertical direction. The movements generally ceased when the acceleration decreased to below 10 milligals. The main periods of the long waves declined during this period from about 30 to 15 seconds, but the seismograms also indicate longer periods, of about 1 to 3 minutes, which may have some connection with the seiches. The calculated periods for the basins where waves were observed are, assuming one node, in most places between 1 and 3 minutes. In England, standing oscillations were recorded in water reservoirs at Margate, Chichester, and Portsmouth during the earthquake. The periods cannot be determined from the records, but the calculated periods vary from 15 to 25 seconds, which corresponds fairly closely with the 22 seconds given by Kew Observatory as the period of the long waves of the earthquake. The maximum amplitude in the reservoirs was 2 inches. Seiches in Norway during the Lisbon earthquake of November 1, 1755, and progressive waves during the Kansu earthquake of December 16, 1920, are briefly discussed.

Dredgings in the freshwater lakes of Norway

Dredgings in the freshwater lakes of Norway