| 1. |
- Ahlbeck, Ida, et al.
(författare)
-
Rearing environment affect important life skills in pikeperch (Sander lucioperca)
- 2012
-
Ingår i: Boreal environment research. - 1239-6095 .- 1797-2469. ; 17:3-4, s. 291-304
-
Tidskriftsartikel (refereegranskat)abstract
- The effect of rearing environment on the behaviour of young-of-the-year pikeperch (Sander lucioperca) bred at three different production facilities was investigated. Two groups were reared in semi-natural ponds and one group in indoor tanks. Exploratory, foraging and anti-predator behaviours were studied in aquarium experiments. There were no significant differences between pond- and tank-reared fish in reluctance to explore their new environment, but pond-reared fish spent significantly more time in macro-vegetation. Pond-reared fish were significantly faster to start foraging on live prey (Neomysis integer) that they had not encountered before. As compared with tank-reared fish, pond-reared fish were also significantly more active in their anti-predator response. Rearing environment obviously influences the development of important life skills. These differences may impact the success rate when stocking young-of-the-year pikeperch into natural waters.
|
|
| 2. |
- Aldvén, David, 1986, et al.
(författare)
-
Environmental cues and downstream migration of anadromous brown trout (Salmo trutta) and Atlantic salmon (Salmo salar) smolts
- 2015
-
Ingår i: Boreal environment research. - 1239-6095 .- 1797-2469. ; 20:1, s. 35-44
-
Tidskriftsartikel (refereegranskat)abstract
- Several environmental cues have been suggested to govern the initiation of the downstream migration of smolts (e.g. light, temperature and discharge). Here we investigated the effect of these cues on the initiation of the downstream migration in anadromous brown trout and Atlantic salmon in a small river on the Swedish west coast during two consecutive years. The total smolt production was assessed using a smolt trap and by modelling data from standardized electrofishing. The results show that it is possible to estimate smolt numbers using electrofishing, but that the model had a tendency to overestimate the number of smolts from electrofishing as compared with that from captures with the smolt trap. Discharge had the greatest effect on downstream migration, but temperature was also important when there was no increase in discharge. These results reveal that discharge and temperature govern the initiation of downstream migration but their effect may depend on the amount of precipitation
|
|
| 3. |
- Andersson, Lotta, 1958-
(författare)
-
Annual variability of nitrogen concentrations and export from forested catchments : A consequence of climatic variability, sampling strategies or human interference?
- 2000
-
Ingår i: Boreal environment research. - 1239-6095 .- 1797-2469. ; 5:3, s. 221-233
-
Tidskriftsartikel (refereegranskat)abstract
- This study was based on the data from 18 years of monitoring in six forested catchments. The aim was to find links between annual estimates of export and concentrations of NO3-N and organic N and hydroclimatological factors, sampling strategy and human interference. A topography-based wetness index was used to assess whether the effects of forestry activities depended on prevailing wetness conditions. For organic N, annual runoff was the main explaining factor in three catchments. The flow condition during sampling was for organic N the main explaining factor in three and for NO3-N in one catchment. Effects of clear-cutting of 14% in one catchment were observed. For organic N, the model could be improved by considering clear-cutting in wet areas only. The southernmost catchment, but also the northernmost catchment with the lowest deposition, showed links to atmospheric deposition, demonstrating that deposition can cause a significant direct response in streamwater concentrations in nutrient-poor catchments.
|
|
| 4. |
- Berkström, Charlotte, et al.
(författare)
-
Rapid effects of a fishing closure on whitefish (Coregonus maraena) in the northern Baltic Sea
- 2021
-
Ingår i: Boreal Environment Research. - 1239-6095 .- 1797-2469. ; 26, s. 89-104
-
Tidskriftsartikel (refereegranskat)abstract
- Areas closed to fishing year-round (no-take zones, NTZs) or during spawning time (spawning closures) are used as a management tool to increase declining fish populations. We evaluated the effects of a 147 km2 NTZ and a 3980 km2 spawning closure on whitefish populations in the northern Baltic Sea, and also accounted for fish consumption by seals and cormorants. Fish monitoring with multimesh gillnets in 2011–2016 showed a significant increase in catch per unit effort (CPUE) of mature whitefish (> 30 cm) both in the spawning closure and the NTZ compared with the reference area open to fishing. The rate of increase was significantly higher in the NTZ than in the spawning closure. Our results suggest that NTZs may strengthen coastal fish populations in temperate regions and that also seasonal closures under a critical period of the life cycle may benefit the populations.
|
|
| 5. |
- Blenckner, Thorsten, et al.
(författare)
-
Atmospheric circulation and its impact on ice phenology in Scandinavia
- 2004
-
Ingår i: Boreal environment research. - 1239-6095 .- 1797-2469. ; 9:5, s. 371-380
-
Tidskriftsartikel (refereegranskat)abstract
- Atmospheric circulation is important in affecting surface climate and ecosystems. In this study, we compared the impact of north-atlantic and regional atmospheric circulation, as represented by the North Atlantic Oscillation (NAO) index and a set of regional circulation indices, on ice phenology of 50 Scandinavian lakes. Both ice freeze and ice break-up dates were coherent over the whole region and were significantly correlated with both types of circulation indices. Correlations were especially strong for regional circulation indices. The application of regional indices, here for the first time related with ice data over a large area, allowed the determination of the type (i.e. meridional/ zonal wind and cyclonic/anticyclonic conditions) of atmospheric circulation influencing the ice phenology. The results suggest that regional circulation indices are very useful tools, in addition to global circulation, to improve the understanding of the interaction between ecosystem processes and climate.
|
|
| 6. |
- Carlos, Diaz-Gil, et al.
(författare)
-
Spatio-temporal composition and dynamics of zooplankton in the Kalmar Sound (western Baltic Sea) in 2009-2010
- 2014
-
Ingår i: Boreal Environment Research. - 1239-6095 .- 1797-2469. ; 19:4, s. 323-335
-
Tidskriftsartikel (refereegranskat)abstract
- In pelagic food webs, zooplankton is the link between lower and higher trophic levels. It is thus essential to know how the zooplankton community structure varies with its environment. We investigated the seasonal and spatial variation in the zooplankton diversity and community structure during two consecutive years in the Kalmar Sound, along the Swedish east coast, an area with a strong bathymetric gradient and of high ecological importance for e.g. commercial fish species. Two zooplankton communities were identified in the area: a coastal/estuarine community in the south and an open-water community in the north. They were separated mainly by differing salinity and temperature conditions. Biodiversity increased from spring to autumn and was higher in the open waters.
|
|
| 7. |
- Carlsson, Björn, 1980-, et al.
(författare)
-
Investigating the effect of a wave-dependent momentum flux in a process oriented ocean model
- 2009
-
Ingår i: Boreal environment research. - 1239-6095 .- 1797-2469. ; 14:1, s. 3-17
-
Tidskriftsartikel (refereegranskat)abstract
- New expressions of the drag coefficient were developed using measurements from the Östergarnsholm site in the Baltic Sea. The drag coefficient was significantly lower in the presence of waves travelling faster than the wind (swell). The expressions were implemented in an oceanographic process-oriented model in a 45-year simulation. Since no wave information was included we did an analysis of the potential impact of swell on an ocean model. Current velocity and surface stress were significantly altered during periods with low wind speed but the temperature and the mixing depth in the ocean were not significantly changed. The implementation of the swell effect in a process oriented ocean model is thus of limited importance. There is, however, an indication that for studies of current velocity it is crucial to have a correct description of the drag coefficient.
|
|
| 8. |
- Claremar, Björn, et al.
(författare)
-
Deposition of acidifying and neutralising compounds over the Baltic Sea drainage basin between 1960 and 2006
- 2013
-
Ingår i: Boreal Environment Research. - 1239-6095 .- 1797-2469. ; 18:6, s. 425-445
-
Tidskriftsartikel (refereegranskat)abstract
- This study produced a gridded database of acidifying and eutrophying deposition in the Baltic Sea and its drainage basin for the period 1960-2006. Data from various data sets were combined to generate monthly atmospheric (wet) deposition of cations (Ca2+, Mg2+, Na+, K+ and NH4+) and anions (SO42-, NO3- and Cl-). Output of a chemical transport model and interpolated measurements were used, and when these were not available, trends and seasonal cycles were constructed from historical emissions and deposition data. These methods lose some spatial patterns, but the mean trends reflect the influence of east-European emissions more than earlier studies with more westerly-centred observations. The calculated depositions of sulphur, nitrogen and calcium (correlated with sulphur emission) increased from 1960 to 1990 and then decreased until 2006. The trend is most evident for sulphur with a 100% increase followed by a 73% decrease.
|
|
| 9. |
- Danielsson, Åsa, et al.
(författare)
-
Effects of re-oxygenation and bioturbation by the polychaete Marenzelleria arctia on phosphorus, iron and manganese dynamics in Baltic Sea sediments
- 2018
-
Ingår i: Boreal environment research. - : FINNISH ENVIRONMENT INST. - 1239-6095 .- 1797-2469. ; 23, s. 15-28
-
Tidskriftsartikel (refereegranskat)abstract
- Sediments underlying hypoxic or anoxic water bodies constitute a net source of phosphorus to the bottom water. This source has the potential to enhance eutrophication. Benthic fluxes of dissolved phosphorus, iron and manganese were measured from hypoxic, normoxic, and normoxic bioturbated by the invasive polychaete Marenzelleria arctia sediment in a mesocosm experiment. The highest benthic phosphorus efflux was detected in mesocosms with the hypoxic treatment. Normoxic, bioturbated sediments led to weaker retention of phosphorus compared to oxic, defaunated sediments. Both iron and manganese fluxes increased under bioturbated conditions compared to defaunated sediments. This study shows that re-oxygenation of previously anoxic coastal sediments enhance phosphorus retention in the sediments. Colonisation by M. arctia induce strong mobilisation of iron and manganese due to its intense bioirrigation, which facilitates organic matter degradation and decreases the phosphorus retention by metal oxides in sediment.
|
|
| 10. |
- Danielsson, Åsa
(författare)
-
Influence of hypoxia on silicate concentrations in the Baltic Proper (Baltic Sea)
- 2014
-
Ingår i: Boreal environment research. - : Finnish Environment Institute. - 1239-6095 .- 1797-2469. ; 19:4, s. 267-280
-
Tidskriftsartikel (refereegranskat)abstract
- Silica (Si) is a key nutrient for diatoms. Over the last century, Si concentrations within the Baltic Sea decreased significantly. This is mainly attributed to ongoing eutrophication, increased production and subsequent deposition and accumulation of organic matter including biogenic silica. As a consequence of the eutrophication, hypoxic and anoxic bottom waters have spread affecting nutrient cycling. This paper looks at the potential impact of oxygen on dissolved silica (DSi). It presents a statistical analysis of the relationship between DSi concentrations and oxygen conditions (O-2) in the deep water of the Baltic Proper. The idea is not new, but this is the first time it is studied in more detail in this area. Regression analysis shows that DSi concentrations decrease significantly with O-2 concentrations, and that the major intrusion of saline water in 1993 strengthened this relationship. Increased hypoxia will significantly affect the cycling of Si in the Baltic Sea.
|
|
| 11. |
- Denfeld, Blaize A., et al.
(författare)
-
Temporal and spatial carbon dioxide concentration patterns in a small boreal lake in relation to ice cover dynamics
- 2015
-
Ingår i: Boreal environment research. - 1239-6095 .- 1797-2469. ; 20:6, s. 679-692
-
Tidskriftsartikel (refereegranskat)abstract
- Global carbon dioxide (CO2) emission estimates from inland waters commonly neglect the ice-cover season. To account for CO2 accumulation below ice and consequent emissions into the atmosphere at ice-melt we combined automatically-monitored and manually- sampled spatially-distributed CO2 concentration measurements from a small boreal ice-covered lake in Sweden. In early winter, CO2 accumulated continuously below ice, whereas, in late winter, CO2 concentrations remained rather constant. At ice-melt, two CO2 concentration peaks were recorded, the first one reflecting lateral CO2 transport within the upper water column, and the second one reflecting vertical CO2 transport from bottom waters. We estimated that 66%–85% of the total CO2 accumulated in the water below ice left the lake at ice-melt, while the remainder was stored in bottom waters. Our results imply that CO2 accumulation under ice and emissions at ice-melt are more dynamic than previously reported, and thus need to be more accurately integrated into annual CO2 emission estimates from inland waters.
|
|
| 12. |
- Enmar, Linda, et al.
(författare)
-
A note on ADCP-based indirect observations of turbulence
- 2016
-
Ingår i: Boreal environment research. - 1239-6095 .- 1797-2469. ; 21:1-2, s. 44-52
-
Tidskriftsartikel (refereegranskat)abstract
- A 70-day data set from bottom-mounted ADCPs on the two sides of the Faroe-Bank Channel was analysed using the recorded flow variance and echo intensity in the deeper reaches of the passage as proxies for turbulence. A consistent picture emerged, not least since the data losses (which were ascribed to turbulence-induced activation of the fish-elimination option in the ADCP software) could be shown to co-vary with the internal M-2 tide affecting the vertical shear, which in turn proved to be correlated with the flow variance.
|
|
| 13. |
- Ernfors, Maria, 1973, et al.
(författare)
-
Greenhouse gas dynamics of a well-drained afforested agricultural peatland
- 2020
-
Ingår i: Boreal environment research. - 1239-6095 .- 1797-2469. ; 25, s. 65-77
-
Tidskriftsartikel (refereegranskat)abstract
- About a quarter of the global anthropogenic greenhouse gas emissions are attributable to agriculture, forestry and other land use. Few studies of afforested drained peatlands have measured exchanges of all three major greenhouse gases (GHG) at a given site, leading to uncertainty in estimated GHG budgets. Thus, we measured forest floor exchange of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) at a well-drained afforested peatland in southern Sweden. The CO2 emissions (76 000 kg ha–1 a–1; SE 6 000) were large compared with previous measurements at similar sites, which may have been partly due to a measurement technique that did not underestimate the flux. A net CH4 uptake of 4.4 kg ha–1 a–1 (SE 0.41) and a net N2O emission of 2.7 kg ha–1 a–1 (SE 0.23) were found, which agreed well with published models relating fluxes to stand biomass (CH4 models) or soil C:N ratio (N2O models).
|
|
| 14. |
- Futter, Martyn
(författare)
-
Controls on inorganic nitrogen leaching from Finnish catchments assessed using a sensitivity and uncertainty analysis of the INCA-N model
- 2013
-
Ingår i: Boreal Environment Research. - 1239-6095 .- 1797-2469. ; 18, s. 373-386
-
Tidskriftsartikel (refereegranskat)abstract
- The semi-distributed, dynamic INCA-N model was used to simulate the behaviour of dissolved inorganic nitrogen (DIN) in two Finnish research catchments. Parameter sensitivity and model structural uncertainty were analysed using generalized sensitivity analysis. The Mustajoki catchment is a forested upstream catchment, while the Savijoki catchment represents intensively cultivated lowlands. In general, there were more influential parameters in Savijoki than Mustajoki. Model results were sensitive to N-transformation rates, vegetation dynamics, and soil and river hydrology. Values of the sensitive parameters were based on long-term measurements covering both warm and cold years. The highest measured DIN concentrations fell between minimum and maximum values estimated during the uncertainty analysis. The lowest measured concentrations fell outside these bounds, suggesting that some retention processes may be missing from the current model structure. The lowest concentrations occurred mainly during low flow periods; so effects on total loads were small.
|
|
| 15. |
- Futter, Martyn
(författare)
-
Effects of changing climate on the hydrology of a boreal catchment and lake DOC - probabilistic assessment of a dynamic model chain
- 2014
-
Ingår i: Boreal Environment Research. - 1239-6095 .- 1797-2469. ; 19, s. 66-82
-
Tidskriftsartikel (refereegranskat)abstract
- Uncertainty in future climate projections is widely recognised, yet few impact model studies explore the implications of this uncertainty on catchment hydrological and biogeochemical responses. Here, we report a novel model chain using HBV, INCA-C and MyLake to simulate runoff, snow dynamics, ice cover, soil moisture, lake thermal stratification and in-lake DOC concentrations in Valkea-Kotinen, a headwater lake in a forest-covered boreal catchment. Impact response surfaces (IRSs) were constructed with 63 combinations of changes in temperature (-2 degrees C to +14 degrees C) and precipitation (-10% to +50%). Superimposing probabilistic projections of climate change onto the IRSs, we illustrate the uncertainty in impacts under projected climate change. Projected climate warming is likely to result in drier soils, shorter snow and ice periods, as well as earlier onset and longer duration of lake stratification. In contrast to earlier results, in-lake DOC concentrations are projected to decrease slightly (-6%), primarily due to decreased terrestrial runoff.
|
|
| 16. |
|
|
| 17. |
- Gottschalk, Steffi
(författare)
-
EU reference conditions in Swedish lakes identified with diatoms as palaeoindicators - a review
- 2011
-
Ingår i: Boreal Environment Research. - 1239-6095 .- 1797-2469. ; 16, s. 473-494
-
Forskningsöversikt (refereegranskat)abstract
- This study aims to assess the reference conditions and reference diatom communities for Swedish lakes by summarizing 36 performed palaeolimnological studies. The following results can serve as a tool in the discussion about reference conditions according to the European Water Framework Directive. (1) Finding one general fixed time of prevailing reference conditions for all Swedish lakes is impossible. (2) 1850 AD, as an often applied fixed reference time, is not an appropriate reference time for all Swedish lakes. (3) Reference nutrient and pH conditions for many southern Swedish lakes were prevailing until about 2300 BP. (4) Reference nutrient and pH conditions for many northern Swedish lakes prevailed longer and may even prevail today. (5) Different reference diatom communities can be found: either benthic (both acidophilous and alkaliphilous) or planktonic communities.
|
|
| 18. |
- Hallfors, Heidi, et al.
(författare)
-
Vertical and temporal distribution of the dinoflagellates Dinophysis acuminata and D. norvegica in the Baltic Sea
- 2011
-
Ingår i: Boreal environment research. - 1239-6095 .- 1797-2469. ; 16:2, s. 121-135
-
Tidskriftsartikel (refereegranskat)abstract
- We investigated the distributions of the toxic dinoflagellates Dinophysis acuminata and D. norvegica in the brackish Baltic Sea, and found them to differ both regarding their seasonality and their vertical distribution. Dittophysis acuminata was considerably more abundant, especially in the Gulf of Finland, where we observed an August peak of 14 300 cells l(-1). It occurred in elevated abundances during or after periods of high phytoplankton biomass in early and late summer. Dinophysis norvegica was abundant during a shorter period, peaking one month after the first D. acuminata maximum. While D. norvegica probably is restricted by both salinity and temperature in the northern Baltic Sea, the more tolerant D. acuminata thrives. The results presented here expand the wide range of scenarios in which D. acuminata may bloom worldwide. Both species mainly formed population maxima either in the mixed surface waters or near the thermocline. Dinophysis acuminata usually occurred in the illuminated and nutrient-poor mixed surface layer, but in the presence of light and a nutricline it formed distinct subsurface peaks. Dinophysis norvegica was not as sensitive to darkness and predominantly formed subsurface peaks, even below the euphotic zone. These occurrences were promoted by shallow stratification, and the combination of a deep mixed layer and cool surface waters drew the D. norvegica population closer to the surface. When D. acuminata and D. norvegica co-occurred, their abundances peaked at different depths; this was observed even when both species formed maxima in the surface layer.
|
|
| 19. |
- Hansen, Joakim, 1978-, et al.
(författare)
-
Taxon composition and food-web structure in a morphometric gradient of Baltic Sea land-uplift bays
- 2012
-
Ingår i: Boreal environment research. - 1239-6095 .- 1797-2469. ; 17:1, s. 1-20
-
Tidskriftsartikel (refereegranskat)abstract
- Shallow Baltic Sea bays undergo a process of morphometric isolation from the sea due to post-glacial land uplift. Recent studies have documented that both flora and fauna communities change along this gradient. Changes in taxon composition may in turn alter feeding ecology and trophic relationships. In addition, the relative importance of carbon from terrestrial sources may increase with bay isolation. In accordance with previous studies, we found a change in the community composition of both flora and fauna with bay isolation. Results of stable isotope analysis (δ13C, δ15N) suggested that epiphytes and periphyton are the major carbon sources for most benthic primary consumers, but that their importance in relation to angiosperms and charophytes decreased with bay isolation. The results also indicated that filter feeders utilize terrestrially derived carbon, but its importance could not be critically related to bay isolation. Trophic positions of the consumers were similar across the bay isolation gradient.
|
|
| 20. |
- Hansson, Sture, et al.
(författare)
-
Climate effects on zooplankton biomasses in a coastal Baltic Sea area
- 2010
-
Ingår i: Boreal environment research. - 1239-6095 .- 1797-2469. ; 15:3, s. 370-374
-
Tidskriftsartikel (refereegranskat)abstract
- To evaluate if climate influence zooplankton densities and dynamics in a coastal Baltic Sea area, we performed statistical analyses of two 12-13-year-long data series. The winter (December March) North Atlantic Oscillation index (NAO) was used as the independent variable and monthly biomasses of seven groups of zooplankton as the dependent variables. Most of the statistically significant correlations were obtained for the spring-early-summer period and they all indicate higher zooplankton biomasses after winters with high NAO values (mild winters). This supports results from other Baltic Sea studies, indicating that winter/spring climate is important to the early summer zooplankton community.
|
|
| 21. |
- Hellen, Heidi, et al.
(författare)
-
Summer concentrations of NMHCs in ambient air of the Arctic and Antarctic
- 2012
-
Ingår i: Boreal environment research. - 1239-6095 .- 1797-2469. ; 17:5, s. 385-397
-
Tidskriftsartikel (refereegranskat)abstract
- Summer concentrations of C-2-C-6 non-methane hydrocarbons (NMHCs) were measured in Antarctica and in the Arctic in 2008. The results show that NMHC concentrations are on average five times higher in the Arctic than in Antarctica. In Antarctica, there were few concentration peaks, but during most of the remaining time concentrations were below or close to the detection limits. Over the Arctic pack ice area north of 80 degrees, concentrations of most of the measured NMHCs were always above the detection limits. No differences based on air-mass origin were detected in Antarctica, but samples collected over the central Arctic Ocean showed higher concentrations in air masses being advected from the Kara Sea and the western-central Arctic Ocean. The relatively higher NMHC-to-ethyne molar ratios calculated for samples collected over the central Arctic Ocean suggest additional alkane sources in the region.
|
|
| 22. |
- Hirsikko, Anne, et al.
(författare)
-
Indoor and outdoor air ions and aerosol particles in the urban atmosphere of Helsinki : characteristics, sources and formation
- 2007
-
Ingår i: Boreal environment research. - 1239-6095 .- 1797-2469. ; 12:3, s. 295-310
-
Tidskriftsartikel (refereegranskat)abstract
- We measured air ion size distributions with an air ion spectrometer in the size range of 0.34-40.3 nm both indoors (in July) and outdoors (in August) in Helsinki, Finland in 2004. At the same time we measured particle number concentrations and size distributions with two condensation particle counters (indoors) and differential mobility particle sizer (outdoors). Our main focus was to study new-particle formation in an urban site. We observed new-particle formation indoors almost every day, even many times a day, and four times outdoors. Indoors, the observed growth rates were 2.3-4.9 nm h-' for 1.3-3-nm ions, 6.5-8.7 nm h(-1) for 3-7-nm ions and 5.1-8.7 nm h-' for 7-20-nm ions. Outdoor ions (3-7 nm) grew at rates as large as 15.4 nm h-'. Outdoor ion and particle number concentrations were dependent on the wind direction, whereas indoor concentrations were dependent on ventilation conditions. Secondary particle formation and growth affected concentrations both indoors and outdoors. We concluded, based on our measurement results and simulated penetration of outdoor particles through the ventilation system, that we had indoor sources for secondary particles.
|
|
| 23. |
- Högström, Ulf, et al.
(författare)
-
Momentum fluxes and wind gradients in the marine boundary layer : a multi platform study
- 2008
-
Ingår i: Boreal environment research. - 1239-6095 .- 1797-2469. ; 13:6, s. 475-502
-
Tidskriftsartikel (refereegranskat)abstract
- During five autumn weeks, measurements of turbulent fluxes were obtained in the Baltic Sea at three levels on a 30-m tower and two levels on an ASIS buoy 4 km from the tower together with profiles of wind and temperature. Wave data and SST were obtained from ASIS. In the mean, momentum fluxes measured on the tower and on ASIS during onshore winds agree closely. Dimensionless wind gradients phi(m)(z/L) for (i) stable conditions are linear in z/L (L is the Obukhov length); (ii) unstable, growing sea conditions are much smaller than predicted by 'standard' equations, due to an indirect effect of the boundary layer height. Individual wind profiles extrapolated from ASIS to tower by integration of phi(m)(z/L) deviate by about 0.5 m s(-1) from measured values, but corresponding mean profiles agree well for all levels from 1.18 m to 30 m. This random variation in the wind field is shown to be related to inherent dynamics of the atmospheric surface layer.
|
|
| 24. |
- Jaanus, Andres, et al.
(författare)
-
Changes in phytoplankton communities along a north–south gradient in the Baltic Sea between 1990 and 2008
- 2011
-
Ingår i: Boreal environment research. - 1239-6095 .- 1797-2469. ; 16, s. 191-208
-
Tidskriftsartikel (refereegranskat)abstract
- Evaluation of changes in Baltic Sea phytoplankton communities has been hampered by a lack of quantitative long-term data. We investigated changes in biomass of summer (June–September) phytoplankton over the last two decades (1990–2008) along a north–south gradient in the Baltic Sea. The areas were characterized by different temperature, salinity and nutrient conditions. Thirty taxonomic groups were selected for the statistical analysis. Increases in total phytoplankton, particularly cyanobacterial, biomass were observed in the Gulfs of Bothnia and Finland. In these two areas over the study period cyanobacteria also became abundant earlier in the season, and in the Curonian Lagoon Planktothrix agardhii replaced Aphanizomenon flos-aquae as the most abundant cyanobacterium. In general, water temperature was the most influential factor affecting the summer phytoplankton communities. Our data suggest that temperature increases resulting from climate change are likely to cause basin-specific changes in the phytoplankton communities, which in turn may affect overall ecosystem functioning in the Baltic Sea.
|
|
| 25. |
- Jacobson, Philip, et al.
(författare)
-
Size-dependent diet composition and feeding of Eurasian perch (Perca fluviatilis) and northern pike (Esox lucius) in the Baltic Sea
- 2019
-
Ingår i: Boreal environment research. - 1239-6095 .- 1797-2469. ; 24, s. 137-153
-
Tidskriftsartikel (refereegranskat)abstract
- To understand food web dynamics, knowledge about factors influencing trophic interactions is fundamental. Using stomach content analysis, we investigated size-dependent predator-prey relations of two coastal predatory fish in the Baltic Sea: perch (Perca fluviatilis) and northern pike (Esox lucius). Perth undergo two ontogenetic diet shifts, from zooplankton to macroinvertebrates at ca. 50 mm; and then to fish at ca. 250 mm. For pike, all sizes (103-810 mm) fed almost exclusively on fish. The fish prey of perch and pike was predominantly three-spined stickleback in spring, and gobiids in late summer. The mean and maximum prey:predator size ratio was larger, while the minimum was smaller for pike compared with perch. Perch and pike fed on smaller-sized gobiids, three-spined and nine-spined stickleback compared within the environment. Our results on size-dependent diets of perch and pike is useful for quantitative analyses of food-web interactions and for ecosystem-based management.
|
|
| 26. |
- Johansson, Julia M., et al.
(författare)
-
The European heat wave of 2018 and its promotion of the ozone climate penalty in southwest Sweden
- 2020
-
Ingår i: Boreal Environment Research. - 1239-6095 .- 1797-2469. ; 25, s. 39-50
-
Tidskriftsartikel (refereegranskat)abstract
- The ozone concentration ([O-3]), temperature (T) and vapour pressure deficit (VPD) during the 2018 heat wave (HW) was compared with conditions from 2013-2017. The study included one coastal and two inland sites in southwest Sweden. The positive relationship between [O-3] and T was stronger in 2018. The average daytime T from April-September was higher by 2.0-2.4 degrees C in 2018. The VPD was strongly and positively affected by the 2018 HW. The daytime mean [O-3] was enhanced by 7-12% in 2018. The relationship between hourly daytime [O-3] and T, as well as that between the daily maximum [O-3] and daily maximum T, was steeper in 2018. The stronger promotion of [O-3] by T in 2018 was possibly partly a result of dry conditions causing stomatal closure of vegetation and thus a weaker O-3 sink. If HWs like that in 2018 become more common, they can be expected to promote higher [O-3] and risk larger health and ecosystem effects.
|
|
| 27. |
- Jönsson, Oskar, et al.
(författare)
-
Air pollution episodes in Stockholm regional background air due to sources in Europe and their effects on human population
- 2013
-
Ingår i: Boreal environment research. - 1239-6095 .- 1797-2469. ; 18:3-4, s. 280-302
-
Tidskriftsartikel (refereegranskat)abstract
- Using air quality measurements, we categorized air pollution according to source sectors in a rural background environment in southern Sweden based on hourly air-mass backward trajectories during 1997-2010. Concentrations of fine (PM2.5) and sum of fine and coarse particulate matter (PM10), accumulation mode particle number, black carbon and surface ozone were 4.0, 3.9, 4.5, 6.8 and 1.3 times higher, respectively, in air masses from the southeast as compared with those in air masses from the cleanest sector in the northwest, consistent with air-mass transport over areas with relatively high emissions of primary particulate matter (PM) and secondary PM precursors. The highest ultrafine particle numbers were associated with clean air from the northwest. We estimate that almost 7.8% and 0.6% higher premature human mortality is caused by PM2.5 and ozone exposure, respectively, when air originates from the southeast as compared with that when air originates from the northwest. Reductions of emissions in eastern Europe would reduce the highest air pollution concentrations and associated health risks. However, since air masses from the southwest are more frequent, emissions in the western part of Europe are more important for annual mean premature mortality.
|
|
| 28. |
|
|
| 29. |
- Kjellsson, Joakim, 1986-, et al.
(författare)
-
Surface drifters and model trajectories in the Baltic sea
- 2012
-
Ingår i: Boreal environment research. - 1239-6095 .- 1797-2469. ; 17:6, s. 447-459
-
Tidskriftsartikel (refereegranskat)abstract
- Results from recent deployments of surface drifters in the Baltic Sea are presented. For the first time ever, the realism of model-generated trajectories was assessed by a statistical com- parison with trajectories of SVP drifters. The absolute dispersion (i.e. the distance from the initial point as a function of time) was found to be somewhat underestimated by the model trajectories. A severe underestimation of the relative dispersion (pair separation) was also noted, which may, to some extent, be due to the limited resolution of the model. However, the relative dispersion was also found to be very dependent on the initial separation of the model trajectory pairs. After filtering the inertial oscillations, a good agreement of the veloc- ity auto-correlations between the drifters and model trajectories was found. A discussion on the impact of these results on future trajectory modelling in the Baltic Sea is also provided.
|
|
| 30. |
- Kulmala, Markku, et al.
(författare)
-
CO2-induced terrestrial climate feedback mechanism : From carbon sink to aerosol source and back
- 2014
-
Ingår i: Boreal environment research. - 1239-6095 .- 1797-2469. ; 19, s. 122-131
-
Tidskriftsartikel (refereegranskat)abstract
- Feedbacks mechanisms are essential components of our climate system, as they either increase or decrease changes in climate-related quantities in the presence of external forcings. In this work, we provide the first quantitative estimate regarding the terrestrial climate feedback loop connecting the increasing atmospheric carbon dioxide concentration, changes in gross primary production (GPP) associated with the carbon uptake, organic aerosol formation in the atmosphere, and transfer of both diffuse and global radiation. Our approach was to combine process-level understanding with comprehensive, long-term field measurement data set collected from a boreal forest site in southern Finland. Our best estimate of the gain in GPP resulting from the feedback is 1.3 (range 1.02-1.5), which is larger than the gains of the few atmospheric chemistry-climate feedbacks estimated using large-scale models. Our analysis demonstrates the power of using comprehensive field measurements in investigating the complicated couplings between the biosphere and atmosphere on one hand, and the need for complementary approaches relying on the combination of field data, satellite observations model simulations on the other hand.
|
|
| 31. |
- Langner, Joakim, et al.
(författare)
-
Atmospheric input of nitrogen to the Baltic Sea basin : present situation, variability due to meteorology and impact of climate change
- 2009
-
Ingår i: Boreal environment research. - 1239-6095 .- 1797-2469. ; 14, s. 226-237
-
Tidskriftsartikel (refereegranskat)abstract
- We present estimates of the present and future deposition of atmospheric nitrogen into the Baltic Sea made using the Eulerian chemical transport model MATCH, and compare these with earlier model estimates. The average total nitrogen deposition for periods of five to ten years from 1992 to 2001 was estimated to be in the range of 261–300 Gg N yr–1.The deposition across the whole catchment area for 2001 was estimated to be 1.55–1.73 Tg N yr–1. Inter-annual variability of nitrogen deposition into the Baltic Sea was calculated to be in the range of 5.1%–8.0%. Investigating one climate change scenario using emissions for year 2000 indicated a rather small impact on total deposition of nitrogen due to climate change, i.e. increase of total nitrogen deposition by ~5% by the end of the 21st century as compared with present conditions. The combined effect of climate change and future changes in anthropogenic emissions of nitrogen to the atmosphere remains an open question. Additional climate change scenarios using different combinations of global and regional climate models and greenhouse gas emission scenarios need to be explored.
|
|
| 32. |
- Lundberg, Peter
(författare)
-
O that awful deepdown torrent
- 2015
-
Ingår i: Boreal environment research. - 1239-6095 .- 1797-2469. ; 20:1, s. 62-74
-
Tidskriftsartikel (refereegranskat)abstract
- An overview of the deep-water flow from the Nordic Seas through the Faroe-Bank Channel and the Denmark Strait into the North Atlantic proper is given. These fluxes are of considerable importance for the global thermohaline circulation, and it is outlined how they can be modeled on the basis of rotating hydraulic theory for zero-as well as finite-potential-vorticity flow. The hydraulic framework is also shown to be useful for analyzing various dynamic features characterizing the deep-water flow.
|
|
| 33. |
- Malmaeus, Mikael, et al.
(författare)
-
Estimating the amount of mobile phosphorus in Baltic coastal soft sediments of central Sweden
- 2012
-
Ingår i: Boreal environment research. - 1239-6095 .- 1797-2469. ; 17:6, s. 425-436
-
Tidskriftsartikel (refereegranskat)abstract
- A new dataset based on 102 sediment cores was examined to estimate the amount of phosphorus (P) that will eventually be released to the water column from the Baltic coastal sediments along the Swedish coast between Öregrund and Oxelösund. Total P (P tot) concentration in the surface sediments varied between 840 and 7100 μg g -1 dry weight (dw) with an average of 1650 μg g -1 dw. In deep sediments, the P tot concentration was around 1000 μg g -1 with small variation. The difference between surface concentration and the stable, deeper, concentration represents P to be released, i.e. the mobile P. Pools of mobile P varied between 1.5 and 18.2 g m -2. Correlations between surface P tot concentrations and amounts of mobile P were strong (r 2 = 0.88). We estimate the amount of mobile P in the coastal sediments of the investigated region to be between 1000 and 4000 tonnes. Assuming a turnover time of the mobile P between three and ten years gives an average annual P release of 100-1300 tonnes yr -1.
|
|
| 34. |
|
|
| 35. |
|
|
| 36. |
- Mattila, Johanna
(författare)
-
Variations in the amount and composition of phosphorus in settling particles in the northern Baltic Sea archipelagos
- 2019
-
Ingår i: Boreal Environment Research. - 1239-6095 .- 1797-2469. ; 24, s. 63-77
-
Tidskriftsartikel (refereegranskat)abstract
- Quantification of the downward flux of phosphorus (P) in the water column is essential for understanding the fates and pathways of different P forms and to establish mass-balances in aquatic systems such as the Baltic Sea. In this study, we investigated the amount and composition of settling P in sediment trap material, as well as the seasonal and spatial variation of the material in four archipelago areas along the Swedish and Finnish coasts of the Baltic Proper. It was found that potentially mobile and immobile forms of P make up roughly equal shares of the total P in settling material, implying that, over time, around half of the settling P will be mobilized in the sediments. We also found substantial temporal and spatial variation in terms of amounts and composition of settling P that may partly be explained by differences in primary production and resuspension.
|
|
| 37. |
- Metsamaa, Liisa, et al.
(författare)
-
Recognising cyanobacterial blooms based on their optical signature : a modelling study
- 2006
-
Ingår i: Boreal environment research. - 1239-6095 .- 1797-2469. ; 11:6, s. 493-506
-
Tidskriftsartikel (refereegranskat)abstract
- Mass populations of cyanobacteria are increasingly attracting the attention of environment agencies, water authorities, and human and animal health organizations, since they can present a range of water quality and treatment problems as well as hazards to human and animal health. The problem is especially severe in the Baltic Sea where cyanobacterial blooms occur every summer covering areas of more than 100 000 km(2). We studied optical properties of several phytoplankton species (including cyanobacteria) present in the Baltic Sea region. The measurements results were used in a bio-optical model together with optical properties of other phytoplankton species from literature. Our results show that cyanobacteria have a characteristic double feature (peak at 650 nm and phycocyanin absorption feature near 630 nm) in their reflectance spectra which can be detected by remote sensing instruments. Our estimation for the open Baltic Sea waters shows that concentration of chlorophyll has to be 8-10 mg m(-3) before the double feature becomes detectable by remote sensing instruments which spectral resolution is 10 nm and signal-to-noise-ratio is 1000:1. Therefore, it is highly unlikely that remote sensing can be used for early warning of emerging potentially harmful blooms as chlorophyll concentrations higher than 4 mg m(-3) qualify as blooms here.
|
|
| 38. |
- Myrberg, Kai, et al.
(författare)
-
Validation of three-dimensional hydrodynamic models of the Gulf of Finland
- 2010
-
Ingår i: Boreal environment research. - 1239-6095 .- 1797-2469. ; 15:5, s. 453-479
-
Tidskriftsartikel (refereegranskat)abstract
- A model-intercomparison study was conducted, the first of its kind for the Baltic Sea, whose aim was to systematically simulate the basic three-dimensional hydrographic properties of a realistic, complex basin. Simulations of the hydrographic features of the Gulf of Finland for the summer autumn of 1996 by six three-dimensional hydrodynamic models were compared. Validation was undertaken using more than 300 vertical hydrographic profiles of salinity and temperature. The analysis of model performance, including averaging of the ensemble results, was undertaken with a view to assessing the potential suitability of the models in reproducing the physics of the Baltic Sea accurately enough to serve as a basis for accurate simulations of biogeochemistry once ecosystem models are incorporated. The performance of the models was generally satisfactory. Nevertheless, all the models had some difficulties in correctly simulating vertical profiles of temperature and salinity, and hence mixed layer dynamics, particularly in the eastern Gulf of Finland. Results emphasized the need for high resolution in both vertical and horizontal directions in order to resolve the complex dynamics and bathymetry of the Baltic Sea. Future work needs to consider the choice of mixing and advection schemes, moving to higher resolution, high-frequency forcing, and the accurate representation of river discharges and boundary conditions.
|
|
| 39. |
|
|
| 40. |
- Nteziryayo, Love-Raoul, et al.
(författare)
-
Sediment DSi and DIP fluxes under changing oxygen availability in bottom waters
- 2018
-
Ingår i: Boreal environment research. - Helsinki, Finland : Suomen Ymparistokeskus (Finnish Environment Institute). - 1239-6095 .- 1797-2469. ; 23, s. 159-174
-
Tidskriftsartikel (refereegranskat)abstract
- In the present study, we investigated how sediment fluxes of dissolved silica (DSi) and dissolved inorganic phosphorus (DIP) were affected by dissolved oxygen (DO) availability in bottom waters. Sediments from two sites in the Baltic proper were incubated under changing oxygen conditions. Our results show that when DO availability decreased from oxic to hypoxic level, the average DSi fluxes decreased significantly at the two sites from 2.12 +/- 0.04 to 0.87 +/- 0.18 and from 2.37 +/- 0.09 to 1.91 +/- 0.55 mmol Si m(-2) d(-1), respectively. Average DIP fluxes increased significantly at one site from 0.06 +/- 0.01 to 0.14 +/- 0.02 mmol P m(-2) d(-1), but not at the other (from 0.06 +/- 0.01 to 0.07 +/- 0.01 mmol P m(-2) d(-1)). These results indicate that a change from highly oxic to hypoxic conditions in bottom waters may decrease DSi fluxes and increase DIP fluxes. However, sediment characteristics can lead to spatial differences in the response of DSi and DI Pfluxes to oxygen availabilit.
|
|
| 41. |
- Ogonowski, Martin, 1980-, et al.
(författare)
-
Status and vertical size distributions of a pelagic mysid community in the northern Baltic proper
- 2012
-
Ingår i: Boreal environment research. - 1239-6095 .- 1797-2469. ; 18:1, s. 1-18
-
Tidskriftsartikel (refereegranskat)abstract
- We report on abundance, biomass, trophic position and vertical size distribution of pelagic mysids (Mysis mixta, Mysis relicta/salemaai, Neomysis integer) in a coastal Baltic Proper area. As compared with the situation in this area in the 1980s, the formerly dominating M. mixta has declined and the total mysid biomass decreased by 50%. Neomysis integer now constitutes the bulk of the mysids. Stable isotopes indicate that they feed on a lower trophic level than Mysis spp., and M. relicta appears more carnivorous than M. mixta. For N. integer, size increases with depth and decreases with in situ light. This was not found for Mysis spp., probably due to their narrow size span and smaller sample size than for N. integer. In N. integer, in situ light explained the size variation with depth better than temperature, indicating that this variation is a response to predation rather than size-related thermal preference.
|
|
| 42. |
- Pekka, Larissa, et al.
(författare)
-
Assessing pollution in the Kola River, northwestern Russia, using metal concentrations in water and bryophytes
- 2008
-
Ingår i: Boreal environment research. - Helsinki. - 1239-6095 .- 1797-2469. ; 13:1, s. 15-30
-
Tidskriftsartikel (refereegranskat)abstract
- Intensive Cu-Ni and Fe mining and smelting in northwestern Russia constitutes a potential risk of pollution in the Kola River. We assessed the degree of pollution along the Kola River by means of overall water quality evaluation and analyses of metals in water samples (dissolved and particulate fractions) and aquatic mosses. The observed pollutant levels were compared with those in unpolluted reference rivers. The results indicate relatively low overall contamination in the Kola River, although Cu and Ni levels are elevated relative to the reference data. Furthermore, PCA ordination models identified clear metal concentration patterns along the river. Al, Cd, Co, Fe, Pb and Zn exhibited an almost continuous increase from the headwaters to the river mouth, whereas As, Ba, Cu, Mn, Mo and Ni showed their highest concentrations in the headwaters, close to the mining areas, relatively low concentrations in the middle parts of the river and elevated concentrations at the river mouth. Bryophyte analysis appeared to be a more sensitive tool for metal pollution assessment than metal concentrations in water.
|
|
| 43. |
- Peltola, Pasi, et al.
(författare)
-
Tyre stud derived tungsten carbide particles in urban street dust
- 2006
-
Ingår i: Boreal environment research. - Helsinki : Finnish Environment Institute. - 1239-6095 .- 1797-2469. ; 11:3, s. 161-168
-
Tidskriftsartikel (refereegranskat)abstract
- In countries where studded winter tyres are used they contribute to the generation of street dust by grinding the road surface and traction sand into finer particles. At the same time the hard metal tips of the studs, made out of tungsten carbide (WC), wear to finer particles dispersed into the environment. Elevated tungsten concentrations in different sampling media, probably caused by the use of studded tyres, have also been reported. In this study three size fractions of street dust sampled in Turku, Finland, were investigated. Tungsten and various other element concentrations were determined with ICP-MS after total dissolution, pseudo total concentration (aqua regia) and a weaker extraction (1M NH4Ac). A visual analysis was made with a SEM-EDX to study the presence and size fraction of WC particles, which has not been studied before. The total concentrations (median values) of tungsten in the fractions were 9.2 µg g–1 (100 µm–2 mm), 21 µg g–1 (45 µm–100 µm) and 39 µg g–1 (< 45 µm). As expected, tungsten showed a tendency to accumulate into the finer size fractions. However, more surprising was the result that out of all elements determined, tungsten had the greatest (median values) relative enrichment in the fine fraction. In the SEM-EDX analysis particles consisting of tungsten were identified and ruled out to be WC abraded from tyre studs. The WC particles occurred either separately or in clusters with size range of 0.1–1.4 µm.
|
|
| 44. |
- Pers, Charlotta, et al.
(författare)
-
Statistical modelling of the phosphate variations in the Baltic proper
- 1997
-
Ingår i: Boreal environment research. - 1239-6095 .- 1797-2469. ; 2:3, s. 303-315
-
Tidskriftsartikel (refereegranskat)abstract
- A statistical model of the variation of phosphate concentration in the upper layers of the Baltic proper was formed, with the aim of studying the magnitude of this variation and to be able to adjust corrupted time series. The large variation observed is only partially explained by seasonal variations and geographical structures. Despite inclusion of longterm trends and annual variations, the residuals showed a substantial correlation within and between the time series.
|
|
| 45. |
- Pettersson, Catharina, et al.
(författare)
-
Photodegradation of aquatic humic substances : an important factor for the Baltic carbon cycle?
- 1997
-
Ingår i: Boreal environment research. - 1239-6095 .- 1797-2469. ; 2:2, s. 209-215
-
Tidskriftsartikel (refereegranskat)abstract
- Although humic substances (HS) are often considered as chemically stable and non-biodegradable in a marine environment, it is well known that exposure to light will lead to a decomposition of these substances. Laboratory experiments of photodegradation by UV-irradiation of aquatic humic substances and natural water resulted in a rapid and quantitative degradation. Seasonal variations in the humic fraction of the total organic carbon (TOC) was indicated in field studies in humic-rich water in Sweden. The HS/TOC-ratio was considerably higher during the dark part of the year than during the light season. Both the laboratory results and the field studies indicate the potential importance of photodegradation of HS and formation of CO2 for the global carbon cycle, though other mechanisms like microbial degradation are possible. Furthermore, the formation of biodegradable low-molecular weight organic acids from terrestrial humic substances may be essential for partly heterotrophic systems like the Bothnian Bay.
|
|
| 46. |
- Reinap, Ausra, 1973-, et al.
(författare)
-
Forest-edge effects on sea-salt aerosol deposition : a wind-tunnel study using living oak leaves
- 2012
-
Ingår i: Boreal environment research. - 1239-6095 .- 1797-2469. ; 17:3-4, s. 193-209
-
Tidskriftsartikel (refereegranskat)abstract
- Landscape patchiness creates aerodynamic transitions zones that affect the exchange of nutrients and pollutants between the atmosphere and vegetation. Using an artificially generated NaCl aerosol, with its mass-versus-particle-size distribution characterised by an aerodynamic mean particle diameter of 1.6 µm and a geometrical standard deviation of 1.9, we investigate the forest-edge effect on aerosol deposition within a model oak (Quercus robur L.) canopy in a wind tunnel with a smooth up-wind surface, and provide quantitative estimates of deposition rates within the emulated beach-to-forest transition. The deposition rate is maximal around the forest edge with an enhancement factor in relation to the beach deposition of 2.4 for Cl- and 2.0 for Na+. Results are in reasonable agreement with those obtained from deposition models, field studies, and other wind-tunnel based investigations. We find a tendency towards an edge effect also at the downwind forest end, which is in support of model predictions. Estimates of deposition velocities at the edge are 0.06 cms-1 and 0.05 cms-1 for Cl- and Na+, respectively. Because of the edge effect the model forest’s deposition velocity is enhanced, being 1.4 times higher around the edge in comparison with the entire forest. This suggests that field measurements of deposition in the interior of a forest “island” in an otherwise open landscape would underestimate the deposition to the entire forest. Our results can help improve estimates of aerosol-borne inputs of nutrients or pollutants to forests that would experience shifts in meteorological regimes due to changes in climate and forestry practices, in particular with respect to deciduous species in coastal environments where forest-edge effects might be substantial.
|
|
| 47. |
- Riise, Gunnhild, et al.
(författare)
-
Acid rain — a strong external driver that has suppressed water colour variability between lakes
- 2018
-
Ingår i: Boreal environment research. - : FINNISH ENVIRONMENT INST. - 1239-6095 .- 1797-2469. ; 23, s. 69-81
-
Tidskriftsartikel (refereegranskat)abstract
- Increasing water colour observed in lakes in the northern hemisphere is frequently explained by several factors, including the decrease in acid deposition, climate change and recently increased concentrations of Fe. As the anthropogenic sulphate deposition levels off, pressure from an external lake quality driver with regional coverage declines. To inves- tigate the impact of acid rain reduction on lake colour variability, we examined 25 lakes in a lake- district of southeastern Norway by analyzing atmospheric deposition, climate and water chemistry data from 1983 to 2012. We observed a marked shift in lake colour after the wet year 2000, probably triggered by a flush of water that has lifted the base line for lake colour to a higher level. Lakes had synchronous temporal trends of many water quality vari- ables, such as conductivity and several major ions. Our data suggest that this is a response to reduced acid deposition. In contrast, lake colour and colour related variables such as Fe and TOC, showed moderate to low coherence. We propose that declined pressure from a strong external driver promotes the importance of climate variability and local catchment specific processes, giving rise to increased colour variability between lakes with time. Introduction
|
|
| 48. |
- Robroek, Bjorn J. M., et al.
(författare)
-
Microclimatological consequences for plant and microbial composition in Sphagnum-dominated peatlands
- 2014
-
Ingår i: Boreal environment research. - Helsinki, Finland : Finnish Environment Institute. - 1239-6095 .- 1797-2469. ; 19:3, s. 195-208
-
Tidskriftsartikel (refereegranskat)abstract
- In three Scandinavian peatlands we studied to what extent plant and microbial community compositions are governed by local-scale microhabitat, with a special interest in the effect of aspect (i.e. exposition of slopes). Despite differences in solar irradiance between the south- and north-facing slopes, maximum temperature was elevated in the south-facing slopes at the most northern site only. Pore-water nutrient concentrations were not affected by aspect, yet dissolved organic carbon concentrations were higher in the south-facing microhabitats. This was likely caused by higher vascular plant biomass. Plant and microbial community composition clearly differed among sites. In all three sites, microhabitat (i.e. prevailing water-table depth) affected the plant and microbial community compositions. Aspect, however, did not affect community composition, even though microclimate significantly differed between the south- and the north-facing aspects at the northernmost site. Our results highlight the complex link between plant community composition, microbial community and environmental conditions, which deserves much more attention than currently in order to fully understand the effects of climate change on peatland ecosystem function.
|
|
| 49. |
- Rutgersson, Anna, 1971-, et al.
(författare)
-
Atmospheric CO2 variation over the Baltic Sea and the impact on air–sea exchange
- 2009
-
Ingår i: Boreal environment research. - 1239-6095 .- 1797-2469. ; 14:1, s. 238-249
-
Tidskriftsartikel (refereegranskat)abstract
- The variability in time and space of the atmospheric molar fraction of CO2 over the Baltic Sea was investigated using data from seven stations from the World Data Center for Greenhouse Gases. The variation on a monthly timescale of CO2 was divided into a global trend, a regional anthropogenic contribution and a natural seasonal cycle. For the Baltic Sea stations the anthropogenic and terrestrial contributions were largest at the coastal sites in the southern Baltic Sea (an offset of 9 ppm), decreasing towards the north over the Baltic Sea (to about 2 ppm). When calculating the air–sea flux of CO2 using the difference in partial pressure between air and sea, uncertainties in the atmospheric molar fraction of CO2 were shown to be of secondary importance as compared with uncertainties in other parameters (< 10%). Realistic uncertainties in the sea surface partial pressure, wind speed or transfer velocity resulted in significantly larger uncertainties in a calculated air–sea flux.
|
|
| 50. |
- Schobesberger, Siegfried, et al.
(författare)
-
Airborne measurements over the boreal forest of southern Finland during new particle formation events in 2009 and 2010
- 2013
-
Ingår i: Boreal environment research. - 1239-6095 .- 1797-2469. ; 18:2, s. 145-163
-
Tidskriftsartikel (refereegranskat)abstract
- Schobesberger, S., Vaananen, R., Leino, K., Virkkula, A., Backman, J., Pohja, T., Siivola, E., Franchin, A., Mikkila, J., Paramonov, M., Aalto, P.P., Krejci, R., Petaja, T. & Kulmala, M. 2013: Airborne measurements over the boreal forest of southern Finland during new particle formation events in 2009 and 2010. Boreal Env. Res. 18: 145-163. We conducted airborne observations of aerosol physical properties over the southern Finland boreal forest environment. The aim was to investigate the lower tropospheric aerosol (up to 4-km altitude) over an area of 250 by 200 km, in particular during new particle formation (NPF) events, and to address the spatial variability of aerosol number concentration and number size distribution. The regional NPF events, detected both airborne and at the ground, with air masses originating from the Arctic or northern Atlantic Ocean were studied throughout the boundary layer and throughout the area covered. Three suitable case studies are presented in more detail. In two of these studies, the concentrations of nucleation mode particles (3-10 nm in diameter) were found considerably higher (up to a factor of 30) in the upper parts of the planetary boundary layer compared to ground-based measurements during the nucleation events. The observed vertical variation can be connected to boundary layer dynamics and interactions between the boundary layer and the lower free troposphere, likely yielding high concentrations of newly formed aerosol particles. Our results suggest that nucleation does not necessarily occur close to the surface. In one presented case we found evidence of NPF occurring in a limited area above cloud, in the complete absence of a regional NPF event.
|
|
