Valtanen, A., Solloch, S., Hartikainen H. & Michaelis, W. 2009: Emissions of volatile halogenated compounds from a meadow in a coastal area of the Baltic Sea. Boreal Env. Res. 14: 915–931.

Chlorine radicals are well-known catalysts in the ozone depletion reactions. This study was undertaken to monitor emissions of chloromethane (CH₃Cl), an important source of chlorine to the troposphere and stratosphere, from a boreal coastal meadow on the shoreline of brackish-water sea. We sampled volatile organic compounds in the atmosphere above two halophytic vegetation types on three days in July 2007, overall 22 measurements were conducted. Two experimental sites were dominated by Salicornia europaea and two sites were covered by mixed vegetation. A variety of substances of anthropogenic and natural origin were identified, the biogenic organic compounds predominating. The vegetation types did not differ markedly in their CH₃Cl flux rates, the daily flux from S. europaea being 10.97 µg m^–2 d^–1 and that from the mixed vegetation 9.92 µg m^–2 d^–1. The recorded fluxes agree well with those reported from other coastal ecosystems. Emissions from boreal coastal areas might therefore be a relevant CH₃Cl source on the local and global scales.

Kesler, M., Vetemaa, M., Saks, L. & Saat, T. 2009: Occurrence of Ligula colymbi (Cestoda) in spined loach (Cobitis taenia) and its effects on reproduction and growth of the host. Boreal Env. Res. 14: 932–936.

The infection prevalence of Ligula colymbi plerocercoids in the spined loach Cobitis taenia inhabiting brackish waters of the Baltic Sea, and the effects of the parasite on the reproduction and growth of the host were studied. There was no significant trend in the infection rate among the different sampling dates in May–July. In total, 24.6% of females and 15.4% of males were infected. In most cases (> 95%) there was only one plerocercoid per host. In females, there was no correlation between the size group of fish and the infection rate, but larger males had significantly higher infection rate than smaller ones. There was no significant correlation between the parasite-host index and length of females. Condition factor of infected females was significantly higher than that of uninfected females. In the uninfected females, average ± SD diameter of oocytes was 1.19 ± 0.10 mm and they were in the trophoplasmatic growth stage. In contrast, only small (< 0.4 mm) oocytes in the protoplasmatic growth stage were found in the infected females, which indicates that they were not able to spawn in the study year. GSI of infected females (median GSI = 0.07) was significantly lower as compared with that of uninfected individuals (median GSI = 13.24).

Holmroos, H., Niemistö, J., Weckström, K. & Horppila, J. 2009: Seasonal variation of resuspension-mediated aerobic release of phosphorus. Boreal Env. Res. 14: 937–946.

In shallow lakes, sediment resuspension can occur frequently. Therefore, the surface sediment is often well oxidized, and the effect of aerobic phosphorus release on internal nutrient loading can be substantial as compared with anoxic phosphorus release. The effect of resuspension on the aerobic release of phosphorus was studied in the field using experimental water columns. The study included three experiments that were conducted in May, August, and October in the shallow Kirkkojärvi basin of Lake Hiidenvesi. The concentrations of suspended solids (SS) and total phosphorus (TP) increased substantially due to the 10-min resuspension event in all the experiments. However, the concentration of soluble reactive phosphorus (SRP) was strongly affected only in August, when the high pH levels promoted SRP release by ligand-exchange reactions. In August, the amount of resuspended TP remaining in the water column 4 hours after the resuspension event equalled the external phosphorus loading of 13 days. Moreover, 46% of the TP increase was in the form of SRP and thus significantly affected the availability of phosphorus for phytoplankton growth. The results demonstrated that resuspension brings substantial amounts of soluble phosphorus into the water column, providing that it occurs during algal blooms when pH in the water column is high. The effect of sediment resuspension on the availability of phosphorus in the shallow Kirkkojärvi basin thus depends on conditions in the water column, which vary with the phase of the growing season.

Hájek, T. 2009: Habitat and species controls on Sphagnum production and decomposition in a mountain raised bog. Boreal Env. Res. 14: 947–958.

I evaluated production and decomposition characteristics of six dominant Sphagnum species in their natural microhabitats distributed along the gradient of water table in an open ombrotrophic bog. The growth in length was much higher in pools and hollows than in hummocks but the resulting annual production was roughly similar in the microhabitats due to a greater shoot density and consequently higher bulk density in hummocks. Although hummocks provided much higher potential for decomposition than hollows, the Sphagnum litter decomposed more slowly in hummocks due to much lower litter quality of the hummock sphagna. Thus the hummock Sphagnum species possess both principal mechanisms participating in maintaining hummocks above hollows — a sufficient production rate and limited decomposition rate. These mechanisms emphasize the role of Sphagnum mosses as autogenic ecosystem engineers controlling also the microhabitat diversification in patterned mires.

Toming, K., Arst, H., Paavel, B., Laas, A. & Nõges, T. 2009: Spatial and temporal variations in coloured dissolved organic matter in large and shallow Estonian waterbodies. Boreal Env. Res. 14: 959–970.

Spatial and temporal variations in coloured dissolved organic matter (CDOM) were studied in two large, shallow and eutrophic Estonian lakes (Peipsi and Võrtsjärv), and in the CDOM-rich Pärnu Bay (in the Gulf of Riga, Baltic Sea). The concentration of CDOM, determined by its absorption coefficient at wavelength [lambda] = 380 nm, ranged from 4.17 to 22.3 m^–1 in Peipsi, from 3.96 to 15.7 m^–1 in Võrtsjärv and from 2.24 to 32.9 m^–1 in Pärnu Bay. The amount of CDOM was spatially variable in all investigated waterbodies. It was highest in the coastal/onshore areas and in the estuaries of the main rivers. It usually decreased from spring towards autumn, and the seasonal patterns were most distinct in the onshore areas. In standing water bodies, the short-term dynamics of discharges had a more significant effect on CDOM concentration in onshore areas than in offshore areas, where the influence of the discharges became visible over a longer period. The results suggest that in large and shallow water bodies the share of the allochthonous component in the CDOM pool decreases towards offshore areas. The impact of CDOM discharged into the inflowing rivers reaches further from shores if the ratio of the catchment area to the volume of the standing water body (C/V) is larger. The influence of precipitation on CDOM absorption proved to be insignificant.

Rasmus, K. & Huttunen, O. 2009: Evaluating the diffuse attenuation coefficient of dry snow by using an artificial light source. Boreal Env. Res. 14: 971–980.

A novel and non-destructive method is proposed for measuring the diffuse attenuation coefficient (K_d) of snow which helps to solve the problem of snow cover disturbance whilst making the measurements. The method is based on the measurement of backscattered upwelling light from an artificial light source above the snow cover. A Monte Carlo model of this measurement system was developed and model runs were made with different sized snow grains. The model produced results that show that the K_d obtained from the new method is higher than the K_d that would be obtained using vertical profiles of downwelling irradiance. The coincidence is better for larger grain sizes. A pilot study of the new measurement system was made in Kilpisjärvi in northern Finland in early January 2003. The measurement results for dry snow show that in the visible wavelengths the attenuation coefficients obtained are in reasonable agreement with those obtained using more traditional methods for snow with similar properties. However, in the near infrared the values are much lower.

Salonen, M., Urho, L. & Engström-Öst, J. 2009: Effects of turbidity and zooplankton availability on the condition and prey selection of pike larvae. Boreal Env. Res. 14: 981–989.

Along with increasing eutrophication the pike (Esox lucius) has decreased in numbers in some parts of the Baltic Sea. We undertook a field study to identify the environmental factors affecting condition of pike larvae around the southwestern coast of Finland. We also sampled the natural zooplankton community to reveal food preferences of pike larvae. Our mixed model showed that larval condition decreased with increasing turbidity, whereas temperature, salinity and stomach content were non-significant factors. One third of the variation in larval condition was explained by sampling site, indicating that site characteristics influenced the condition index significantly. The prey selection index showed that pike larvae preferred adult copepods and cladocerans, whereas they ignored rotifers and seemingly copepod nauplii as well. Together, our data show that food availability and several environmental factors are crucial for the condition of pike larvae, and probably also survival and recruitment.