Virkkula, A., Hillamo, R.E., Kerminen, V.-M. & Stohl, A. 1997. The influence of Kola Peninsula, continental European and marine sources on the number concentrations and scattering coefficients of the atmospheric aerosol in Finnish Lapland. Boreal Env. Res. 2(4): 317–336.
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Laanemets, J., Kononen, K. & Pavelson, J. 1997. Nutrient intrusions at the entrance to the Gulf of Finland. Boreal Env. Res. 2(4): 337–344.
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Hellsten, S.K. 1997. Environmental factors related to water level regulation — a comparative study in northern Finland. Boreal Env. Res. 2(4): 345–367.
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Dauvalter, V. 1997. Metal concentrations in sediments in acidifying lakes in Finnish Lapland. Boreal Env. Res. 2(4): 369–379.
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Pimiä, V., Kankaanpää, H. & Kononen, K. 1997. The first observation of okadaic acid in Mytilus edulis from the Gulf of Finland. Boreal Env. Res. 2(4): 381–385.
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Tolonen, A. 1997. Size-specific food partitioning and growth in benthic whitefish, Coregonus lavaretus (L.), in a subarctic lake. Boreal Env. Res. 2(4): 387–399.
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Virkkula, A., Hillamo, R.E., Kerminen, V.-M. & Stohl, A. 1997. The influence of Kola Peninsula, continental European and marine sources on the number concentrations and scattering coefficients of the atmospheric aerosol in Finnish Lapland. Boreal Env. Res. 2(4): 317–336.
Atmospheric aerosols were measured at Sevettijärvi in Finnish Lapland in 1992–1995. The variation of aerosol concentrations in different air masses has been examined. In polluted air from the Kola peninsula particle number concentrations were often > 10000 cm– 3. In marine and continental air mean particle number concentrations were 60–350 cm– 3 and 200–1 120 cm– 3, respectively. They were lower in air from the Arctic Sea than in air from the Norwegian Sea. This is explained by the difference in the natural sulphur emissions and resulting particle production between these two areas. In marine air, the mean scattering coefficient (ssp) at 550 nm was 2–8 x 10– 6 m–1, in continental air 2–3 x 10– 5 m–1, and in pollution plumes < 9 x 10– 5 m–1. The mean backscatter fraction in marine air, continental air and in pollution plumes was 0.13, 0.11, 0.10, respectively. The impact of the air pollution sources in northern Siberia was detected despite the vicinity of Kola peninsula pollution sources.
Laanemets, J., Kononen, K. & Pavelson, J. 1997. Nutrient intrusions at the entrance to the Gulf of Finland. Boreal Env. Res. 2(4): 337–344.
The nutrient distribution peculiarities below the seasonal thermocline were analysed on the basis of high vertical resolution (2.5 m) data at the entrance area to the Gulf of Finland. Remarkable increase of nutrient concentration and DIN:DIP and a decrease of temperature on the isopycnals in the onshore direction (towards the Finnish coast) were registered. An intrusive finestructure of the temperature and nutrient fields was observed in the warmer side of thermohaline front, which separates the near-shore and open gulf waters. Nutrient-rich intrusions were cold, with a thickness of 5 to 20 m and the largest horizontal scale of about 5 km. The maximum intensities of intrusions, e.g. for phosphorus and silicate were approximately 0.3 µM and 3 µM, respectively. The generation and isopycnic spreading of intrusions is hypothesized as one link in the chain of overall nutrient transport.
Hellsten, S.K. 1997. Environmental factors related to water level regulation — a comparative study in northern Finland. Boreal Env. Res. 2(4): 345–367.
The environmental conditions of the littoral zone were studied in the regulated Lake Ontojärvi and the unregulated Lake Lentua in northern Finland. The general aims of the study were to analyse the environmental factors related to water level regulation in the littoral zone and to produce information for assessing the effects of hydroelectric development in northern lakes. The study was basically carried out by comparing the littoral environments of the two study lakes. The most visible effects of water level regulation were related to the raised water level, which yielded erosion of sandy shores at the beginning of the regulation. Another effect of lake regulation was the altered fluctuation of the water level, which led to bottom instability and increased the size of the frozen and ice penetration zones. The effect of ice penetration was also easy to recognize on the shores of Lake Ontojärvi, where the surface sediment was frozen to a greater depth and across wider areas than in Lake Lentua. Below the freezing zone, the ice just pressed down on the sediment. The shores of Lake Ontojärvi were steeper than those of Lake Lentua, what affected the distribution of bottom types, with sandy bottoms being more common in Lake Lentua than in Lake Ontojärvi. The factors related to site exposure included effective fetch and the shape of the shoreline. The sedimentation level correlated only with the slope and was not predicted by the fetch or shape. The vertical reduction of light was estimated on the basis of water colour. The main environmental factors from the two lakes were used in a discriminant analysis to predict the bottom type distribution of the littoral (r2 = 0.41).
Dauvalter, V. 1997. Metal concentrations in sediments in acidifying lakes in Finnish Lapland. Boreal Env. Res. 2(4): 369–379.
Fifteen lakes in the Finnish Lapland were investigated to study acidification and pollution effects on metal concentrations in sediments. In four lakes the pH was lower than 6.0 and the alkalinity was lower than 50 meq l–1. Contamination factor (Cf, ratio of metal concentration of the top layer to the bottom layer in a sediment core) of Pb (Cf = 10.1–10.4) was high in comparison to other investigated heavy metals, particularly in acidic lakes. Lake acidification results in decreasing Ni, Cu, Zn, Cd, and Al concentrations towards the sediment surface. Reduction of organic material content (loss on ignition) in upper sediments of acidic lakes was also noticed. The buffer capacity index (BCI, ratio of sum of alkaline and alkaline-earth metals (K, Na, Ca, Mg) to Al) was lower in the acidic lakes (0.12–0.36) than in the other studied lakes (0.42–1.34).
Pimiä, V., Kankaanpää, H. & Kononen, K. 1997. The first observation of okadaic acid in Mytilus edulis from the Gulf of Finland. Boreal Env. Res. 2(4): 381–385.
Levels of okadaic acid, a DSP toxin, were determined in the soft tissues of the blue mussel Mytilus edulis. The mussels were collected by divers at Långskär, an island a few kilometres off Tvärminne in the western Gulf of Finland. The dived mussels were placed in plastic baskets at two stations, at Storgadden (59°47´N, 23°19´E) in the western Gulf of Finland, and at Huovari (60°24´N, 27°40´E) in the eastern Gulf of Finland. Due to economical difficulties the mussels couldn´t be systematically sampled by divers. At both stations, between April and September, the mussels were kept for 3–4-week periods in baskets at depths of 5 m and 30 m. After 3–4 weeks, the sampled mussels in the baskets were replaced with the new ones. During each sampling, in Storgadden and Huovari, the mussels from both depths were combined for toxin analysis. Plankton samples were taken from the surface water layer (0–10 m) during mussel sampling. At Storgadden, the mussels sampled in May and at Huovari in July contained small amounts of okadaic acid: 21.7 ± 3.6 (mean ± method error) ng g–1 d.w. and 82.5 ± 16.5 (mean ± method error) ng g–1 d.w. in May and July, respectively. No toxins were detected in samples from August–September. This preliminary study shows that okadaic acid can be detected in Mytilus edulis in the Gulf of Finland, although toxic levels were not found, nor was there found any correlation between the density of dinoflagellates and the okadaic acid levels.
Tolonen, A. 1997. Size-specific food partitioning and growth in benthic whitefish, Coregonus lavaretus (L.), in a subarctic lake. Boreal Env. Res. 2(4): 387–399.
The summer diet of benthic whitefish (Coregonus lavaretus (L.)) was studied in an oligotrophic subarctic lake. The fish were caught with bottom gill net series during two open-water seasons in 1982–1983. Planktonic crustaceans, especially cladocerans, were the most common food of small (< 150 mm) whitefish. The mid-sized fish (150–220 mm) preyed mostly on the larvae and pupae of chironomids, which were also the most frequent prey of larger whitefish during July. Zoobenthos such as molluscs and chironomid larvae were the food most utilized by the largest fish (> 220 mm). The use of zoobenthos increased and that of insect pupae decreased towards the autumn in every size group of fish. Differences were significant within large fish (p < 0.001). Stomach fullness and the frequency of empty stomachs varied markedly from year to year; fluctuations were more pronounced in the larger fish. Between the smallest fish (< 150 mm) and the other size-groups a clear difference was present in the percentage of plankton food (p < 0.001), suggesting the presence of only minimal food competition. Improved growth of fish longer than 150 mm indicated a favorable effect of the diet shift. After the length of 200 mm was attained the diet similarity between size-groups was pronounced. Slow growth was probably caused by intraspecific food competition. After the fish attained the length of 240 mm rapid improvement in growth was observed.