ISSN 1239-6095
© Boreal Environment Research 2005

Contents of Volume 10 Number 1

Hongisto, M. & Joffre, S. 2005: Meteorological and climatological factors affecting transport and deposition of nitrogen compounds over the Baltic Sea. Boreal Env. Res. 10: 1–17.
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Laamanen, M. & Kuosa, H. 2005: Annual variability of biomass and heterocysts of the N2-fixing cyanobacterium Aphanizomenon flos-aquae in the Baltic Sea with reference to Anabaena spp. and Nodularia spumigena. Boreal Env. Res. 10: 19–30.
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Miettinen, J. O., Kukkonen, M. & Simola, H. 2005: Hindcasting baseline values for water colour and total phosphorus concentration in lakes using sedimentary diatoms — implications for lake typology in Finland. Boreal Env. Res. 10: 31–43.
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Nõges, P. & Järvet, A. 2005: Climate driven changes in the spawning of roach (Rutilus rutilus (L.)) and bream (Abramis brama (L.)) in the Estonian part of the Narva River basin. Boreal Env. Res. 10: 45–55.
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Valta-Hulkkonen, K., Kanninen, A., Ilvonen, R. & Leka, J. 2005: Assessment of aerial photography as a method for monitoring aquatic vegetation in lakes of varying trophic status. Boreal Env. Res. 10: 57–66.
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Åström, M., Aaltonen, E.-K. & Koivusaari, J. 2005: Changes in leaching patterns of nitrogen and phosphorus after artificial drainage of a boreal forest — a paired catchment study in Lappajärvi, western Finland. Boreal Env. Res. 10: 67–78.
Abstract
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Hongisto, M. & Joffre, S. 2005: Meteorological and climatological factors affecting transport and deposition of nitrogen compounds over the Baltic Sea. Boreal Env. Res. 10: 1–17.

We studied the variation of the nitrogen deposition to the Baltic Sea with the Eulerian transport-chemistry model Hilatar. We analysed the effects of the climatological and meteorological conditions on the temporal variations of the pollution load to the sea over the period 1993–1998. The nitrogen deposition to the Baltic Sea and the concentrations at coastal stations showed strong monthly, seasonal and inter-annual variations and, apparently, no decrease with declining emissions over the period. We discuss the representativeness of coastal measurements for inferring the deposition flux to the open sea, as well as the episodicity affecting this pollution load. We also compare our results for the nitrogen deposition to the Baltic Sea with the previous estimates and discuss the implications for ecological modelling.
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Laamanen, M. & Kuosa, H. 2005: Annual variability of biomass and heterocysts of the N2-fixing cyanobacterium Aphanizomenon flos-aquae in the Baltic Sea with reference to Anabaena spp. and Nodularia spumigena. Boreal Env. Res. 10: 19–30.

The biomass, abundance of heterocysts and heterocyst frequencies of the N2-fixing cyanobacterium Aphanizomenon flos-aquae and the corresponding environmental parameters were monitored during two separate years near the entrance of the Gulf of Finland. For reference, data on two other N2-fixing cyanobacteria, Anabaena spp. and Nodularia spumigena were collected as well. A. flos-aquae was observed throughout the year, being most abundant in the summer, while Anabaena spp. and N. spumigena were found only during the warmest summer period. A biomass increase of A. flos-aquae was positively associated with temperature and negatively with the DIN:DIP ratio; the highest biomasses were found at temperatures above 10 °C and in molar DIN:DIP ratios less than 10. According to the changes in the heterocyst frequencies, A. flos-aquae had a seasonal N2 fixation strategy in which the maximum frequencies of heterocysts preceded the annual biomass peak.
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Miettinen, J. O., Kukkonen, M. & Simola, H. 2005: Hindcasting baseline values for water colour and total phosphorus concentration in lakes using sedimentary diatoms — implications for lake typology in Finland. Boreal Env. Res. 10: 31–43.

Background and present total phosphorus (TP) concentrations and water colour have been assessed with palaeolimnological methods in 27 lakes in eastern Finland. Sediment samples from core bottoms (sediment depth 29–185 cm) and core tops (sediment depth 0–1 cm) were analysed for diatom assemblages, and TP and water colour were estimated by weighted averaging methods. Changes in DI-TP and water colour between the core bottom and top samples were used for identification of potential reference lakes, as defined by the EU Water Framework Directive. In addition, implications for lake typology in Finland are discussed. Our results suggest that naturally eutrophic lakes may be more common in Finland than previously thought. Water colour, as well as TP, seems to have been subject to considerable changes in many lakes. According to our results, oligotrophic clearwater lakes appear to be little changed from their pre-disturbance conditions, but most of the presently highly coloured lakes have developed towards increasing water colour.
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Nõges, P. & Järvet, A. 2005: Climate driven changes in the spawning of roach (Rutilus rutilus (L.)) and bream (Abramis brama (L.)) in the Estonian part of the Narva River basin. Boreal Env. Res. 10: 45–55.

Increasing water temperature in spring in Estonian inland waters has affected differently the spawning of roach and bream. Within forty years (1951–1990), the spawning of bream shifted, on average, to a ten days earlier period but the range of spawning temperature remained unchanged, while there was no shift in the spawning time for roach, which started to spawn at about three degrees higher water temperature than earlier. The difference between spawning times of roach and bream decreased from an average 22 to 13 days and the difference in average temperatures at the onset of spawning by about 3 °C. Besides water temperature, the timing of spawning was also related to the water level in spring: in years with higher water levels in March or April both fish species started to spawn earlier. The effect of water level changes on spawning was more pronounced in shallower Võrtsjärv than in Lake Peipsi.
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Valta-Hulkkonen, K., Kanninen, A., Ilvonen, R. & Leka, J. 2005: Assessment of aerial photography as a method for monitoring aquatic vegetation in lakes of varying trophic status. Boreal Env. Res. 10: 57–66.

Implementation of the EU Framework Directive for Water Policy requires assessment of the ecological quality of surface waters using reliable, repeatable, quantitative and cost-effective monitoring methods. Digital colour infrared (CIR) aerial photographs representing 16 lakes of varying trophic status in the Vuoksi drainage basin, Finland, were used here to study the usefulness of remote sensing as a method for monitoring aquatic vegetation. The accuracy of the photo-interpretation method was assessed, and its ability to detect differences in the abundance of aquatic vegetation in lakes of varying trophic status was studied. Two measures of vegetation abundance based on the interpretation of aerial photographs, a colonization degree and a relative long-term change in the area of helophytes and nymphaeids, were used. The results indicated that CIR aerial photographs were suitable for mapping helophytic and nymphaeid vegetation and that the colonization degree of helophytes and nymphaeids was consistent with the nutrient content (total phosphorus and total nitrogen) of the lakes as well as with a measure of abundance based on field data.
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Åström, M., Aaltonen, E.-K. & Koivusaari, J. 2005: Changes in leaching patterns of nitrogen and phosphorus after artificial drainage of a boreal forest — a paired catchment study in Lappajärvi, western Finland. Boreal Env. Res. 10: 67–78.

The effect of ditching of boreal (Finnish) peat-rich forest land on leaching patterns of phosphorus and nitrogen was assessed using a paired catchment approach (response stream + control stream) for a 4 + 1 year study period. After the ditching operations, the leaching of the organic nitrogen (TON) decreases, while that of the inorganic nitrogen (ammonium and nitrate) and phosphorus (total reactive P and total non-reactive P) increases. The TON does not decrease as much as TOC does, indicating that the pool of organic material being leached after the ditching is enriched in nitrogen. The increased leaching of ammonium and nitrate after ditching is related most likely to ammonification and nitrification processes in peat biomass after the release of excess surface water. The behaviour of P is complex. The data indicate that the major controls of the determined P fractions are the Fe redox chemistry and the behaviour of Fe hydroxides.
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