Limnological effects of growth and cessation of agricultural land use in Ladoga Karelia: sedimentary pollen and diatom analyses

Reference conditions and changes in limnological conditions during the 20th century have been inferred in a palaeolimnological study of sediments from six lakes of the District of Sortavala, Karelian Republic, Russia. The area is former Finnish territory, which was in intensive use for arable field cultivation until the World War II, when the area was ceded to the Soviet Union. After the war, farming was resumed by cattle sovkhozes, and the fields were mainly used as pasture without regular ploughing. We have studied the history of eutrophication and recovery in some lakes related with the changes of agricultural intensity. The trophic level of the lakes was studied by sedimentary diatom assemblages, including reconstructions of total phosphorus levels in the lakes based on a weighted averaging transfer function. Pollen analyses were used to assess the changes in the land use near the lakes. Valuable background data on all the lakes used in the present study are provided by a doctoral thesis done on their limnology from the 1920s. According to our results, the four lakes situated on the clayey lowlands near the coast of Lake Ladoga were eutrophicating during the first half of the 20th century, and in two of them, a rapid recovery is evident. In two lakes situated in hilly landscape with limited agricultural activities, only minor changes are recorded in the diatom profiles.     

Subarctic catchment water storage and carbon cycling – Leading the way for future studies using integrated datasets at Pallas,Finland

Subarctic ecohydrological processes are changing rapidly, but detailed and integrated ecohydrological investigations are not as widespread as necessary. We introduce an integrated research catchment site (Pallas) for atmosphere, ecosystems, and ecohydrology studies in subarctic conditions in Finland that can be used for a new set of comparative catchment investigations. The Pallas site provides unique observational data and high-intensity field measurement datasets over long periods. The infrastructure for atmosphere- to landscape-scale research in ecosystem processes in a subarctic landscape has recently been complemented with detailed ecohydrological measurements. We identify three dominant processes in subarctic ecohydrology: (a) strong seasonality drives ecohydrological regimes, (b) limited dynamic storage causes rapid stream response to water inputs (snowmelt and intensive storms), and (c) hydrological state of the system regulates catchment-scale dissolved carbon dynamics and greenhouse (GHG) fluxes. Surface water and groundwater interactions play an important role in regulating catchment-scale carbon balances and ecosystem respiration within subarctic peatlands, particularly their spatial variability in the landscape. Based on our observations from Pallas, we highlight key research gaps in subarctic ecohydrology and propose several ways forward. We also demonstrate that the Pallas catchment meets the need for sustaining and pushing the boundaries of critical long-term integrated ecohydrological research in high-latitude environments.     

Bioavailability and radiocarbon age of fluvial dissolved organic matter (DOM) from a northern peatland-dominated catchment: effect of land-use change

The radiocarbon age and biodegradability of dissolved organic matter (DOM) from a northern peat-dominated river system was studied and the effects of land-use were compared. Samples were obtained from streams and ditches comprising sub-catchments of the Kiiminki River, Northern Finland. Sample sites included areas of natural mire, areas subjected to moderate disturbance (ditching to enhance forestry), and areas subjected to serious land use change (agriculture and peat excavation). The study employed a 55 day bioassay that measured the biodegradation potential of surface-water DOM. We identified release of modern (mean 6–13 year old) DOM from natural sites, and material aged up to 1,553 years from disturbed sites. The proportion of biodegradable DOC ranged from 4.1 to 17.9 %, and bacterial DOC removal was modelled using twin-pool and reactivity-continuum (beta distribution) approaches. Bacterial growth efficiency ranged from 0.11 to 0.26 between areas of different land use, and these relatively low values reflect the humic-rich DOM released from boreal peatland. Despite the range of land-use types studied, including intensive peatland excavation areas, there was no detectable relationship between the biological lability of DOM and its radiocarbon age.     

A Bayesian network for analyzing biological acute and long-term impacts of an oil spill in the Gulf of Finland

Knowledge of oil-induced impacts from the literature and experts were used to develop a Bayesian network to evaluate the biological consequences of an oil accident in the low-saline Gulf of Finland (GOF). Analysis was carried out for selected groups of organisms. Subnetworks were divided into subgroups according to a predicted response to oil exposure. Two scenario analyses are presented: the most probable and the worst-case accident.The impact of the most probable accident in the GOF is rather small. In most of the groups studied oil-induced long-term effects are evaluated to be minor at least from the perspective of the whole GOF. After the worst-case accident negative effects are more likely. The model predicts that the most vulnerable groups are auks and ducks. Amphipods, gulls and to a lesser extend littoral fishes and seals may show delayed recovery after an accident. Also annual plant species may be susceptible to oil-induced disturbances.     

Establishing a national ore data file in Finland

Summary The Finnish Ore Data File has already provided valuable experience on building, maintaining, and using an extensive data file with a great diversity of data. The file attempts to accommodate all relevant data on ore deposits in metamorphosed and strongly deformed Precambrian terrain. Because the deposits dealt with are generally well-studied and documented, they provide a great deal of precise information on ore deposits. The question arises as to how the system could be used internationally, especially bearing in mind developing countries. The two problems which should be solved for this purpose are: first, the forms, codes, and programs should be translated from Finnish into English; second, the structure of the file should be simplified to meet the demands of less studied areas and deposits. However, both problems could be resolved relatively easily without changing the basic principles involved.This paper was presented at the International Geological Correlation Program (IGCP) Project 98 entitled Standards for Computer Applications in Resource Studies held at Loen, Norway, September 27–October 1, 1976.     

Nitrogen, Silicon and Zooplankton Controlling the Baltic Spring Bloom: An Experimental Study

The importance of nitrogen, silicon and grazing for the development of the planktonic spring bloom of the transition area between the Baltic Proper and the Gulf of Finland was studied in a laboratory experiment. Water for this experiment was collected prior to the onset of the spring bloom in early April 1991. At this time, inorganic nutrient concentrations were still at their annual maxim. In the experiment, conducted in plastic tanks, the nitrate level was doubled and silicate level tripled by single and combined additions. One tank was filtered with a 100 μm net to exclude large grazers of phytoplankton. Two unmanipulated controls were used. The tanks were maintained at +2 °C for a 3 week period in 12 h of daylight (60 μE m⁻²s⁻¹), during which time their nutrient and phytoplankton dynamics were followed. All added inorganic nitrogen was swiftly taken up inducing rapid phytoplankton growth; consequently, available phosphorus must have met the needs of growth. The results showed the limiting nature of nitrogen on the maximum primary productivity and chlorophyll aconcentration. Silicate additions affected the structure of the phytoplankton assemblage by promoting specifically the growth of the diatomChaetoceros holsaticusSchütt, which produced resting spores at later stages of the bloom, whileChaetoceros wighamiiBrightwell was the dominant diatom species in other tanks. The absence of large grazers had no effect on phytoplankton dynamics.     

Processing of humic-rich riverine dissolved organic matter by estuarine bacteria: effects of predegradation and inorganic nutrients

The bioavailability of predegraded dissolved organic matter (DOM) from a humic-rich, boreal river to estuarine bacteria from the Baltic Sea was studied in 39-day bioassays. The river waters had been exposed to various degrees of bacterial degradation by storing them between 0 and 465 days in dark prior to the bioassay. The resulting predegraded DOM was inoculated with estuarine bacteria and the subsequent changes in DOM quantity and quality measured. During the incubations, dissolved organic carbon (DOC) and oxygen concentrations decreased, indicating heterotrophic activity. Coloured DOM was degraded less than DOC, indicating a selective utilization of DOM, and humic-like fluorescence components increased during the incubations. The amount of DOC degraded was not affected by the length of DOM predegradation. The percentage of bioavailable DOC (%BDOC) was higher in experiment units with added inorganic nitrogen and phosphorus than without addition (on average 13.5 % and 9.0, respectively), but had no effect on the degradation of fresh, non-predegraded, DOC (%BDOC 12.0 %). Bacterial growth efficiency (BGE) was highest (65 ± 2 %) in the units with fresh DOM, and lowest in units with predegraded DOM and no added inorganic nutrients (11 ± 4 %). The addition of inorganic nutrients increased the BGE of predegraded DOM units by an average of 28 ± 4 %. There was no significant effect on BGE by length of predegradation after the initial drop (<3 months). This study suggests that both the length of predegradation and the inorganic nutrient status in the receiving estuary has consequences to carbon cycling and will determine the amount of terrestrial-derived DOC being ultimately assimilated into marine food webs.     

Till and bedrock geochemistry in Sn exploration: A case study

The youngest intrusive phases of the rapakivi granites are known as Sn granites. The endocontact and exocontact zones of the Viipuri rapakivi massif and its satellites have been considered on theoretical grounds as critical areas for Sn deposits. The area between the Viipuri rapakivi massif and its satellite, the Ahvenisto massif, was selected for prospecting as one Sn critical area.Heavy-mineral geochemistry was used in the reconnaissance phase. Samples (10 1) from the surficial part of the till deposits were taken from a sparse sampling grid. Heavy minerals of the samples were concentrated by washing on a riffle box and by subsequent heavy-liquid separation. The non-magnetic heavy fraction was analyzed by XRF. Quite a large and coherent glaciogenic Sn anomaly was found, the head of which terminated in the southern part of the Ahvenisto rapakivi massif.The source of the anomaly was sought by taking basal till and bedrock samples with a tractor-mounted percussion drill. The fine fraction of till was analyzed by AAS and the bedrock samples by XRF and AAS. Mainly on the basis of Sn and Cu anomalies in basal till and bedrock 10 holes were diamond drilled into bedrock. Several topaz-bearing greisen bodies with uneconomic Sn content were penetrated. The results demonstrate the soundness of the theory and the methods used.