Turveraportti kestää kritiikin

Keskustelu

Kirpulla menneisyyteen – järvien pohjakerrostumat kertovat Suomen ilmaston kehityksen

Viime vuosien aikana monen luonnontutkijan huomio on suuntautunut kauas menneisyyteen. Syynä on, yllättävää kyllä, lisääntynyt tarve tuntea tulevaisuutta. Kun luonto muuttuu, pitkää aikaväliä koskevalla ympäristötiedolla on kasvava kysyntä. Sitä tarvitaan erottamaan ihmisen osuus luonnon omasta muutoksesta. Esimerkiksi tulevaa ilmastomuutosta ja se vaikutuksia ennustettaessa luontaisen vaihtelun tunteminen on osoittautunut välttämättömäksi. Tarkka tieto aiemmasta ilmastokehityksestä on erityisen tärkeää ilmastoa kuvaavien mallien toimivuuden ja luotettavuuden testaamisessa

Biogeography and ecology of freshwater chrysophyte cysts in Finland

The occurrence of various chrysophyte cyst morphotypes is unknown in Finland, with the exception of a few isolated lake studies. We set out to chart which cyst types are found in Finland and what their ecological preferences are, focusing on cyst-air temperature relationships that could be further utilized in reconstructing past winter/spring air temperatures and ice-free periods from sedimentary cyst assemblages. Surface sediment samples from lakes across Finland were analysed for their chrysophyte stomatocyst assemblages. Multivariate ecological techniques (e.g. canonical correspondence analysis, principal component analysis) were used to identify the environmental variables that most strongly affected the distribution of the cysts. This survey expanded the known geographical range for several cyst types. Lake water pH and ice-free periods (surrogate for air temperature) explained the statistically significant distribution and composition of the cyst assemblages studied. The results broaden our knowledge of cyst biogeography and strengthen the findings of previous studies of the environmental factors contributing to the occurrence of cysts. Highly variable and rich chrysophyte cyst assemblages in Finland are clearly associated with temperature, pH, electrical conductivity and total phosphorus, with good potential in contemporary and retrospective environmental assessment.Peer reviewe

Mining pollution triggered a regime shift in the cladoceran community of Lake Kirkkojärvi, southern Finland

Mining is one of the key industries in the world and mine water pollution is a serious threat to aquatic ecosystems. Historical monitoring data on the pollution history and impacts in aquatic ecosystems, however, are rarely available, so paleolimnological methods are required to explore the consequences of past pollution. We studied the history of cladoceran community dynamics in Lake Kirkkojarvi, southern Finland, including the periods before, during and after mining. We analyzed the geochemical composition and cladoceran subfossil remains in a Pb-210-dated sediment core to evaluate the magnitude, rate, and direction of cladoceran community changes through time. The cladoceran community was altered significantly by mining activity that occurred during the mid-twentieth century. During more recent times, however, eutrophication effects have overridden the impacts of mining. After mining ceased, the cladoceran community underwent an abrupt regime shift towards taxa that reflect more eutrophic conditions. This change was caused by intensive farming activity and fertilizer use over the past few decades. The recent history of Lake Kirkkojarvi is a textbook example of a regime shift triggered by multiple human-caused stressors. Our findings also highlight the utility of cladocerans as bio-indicators in pollution research and illustrate the sensitivity of aquatic ecosystems to anthropogenic modification.Peer reviewe

Paleolimnological Fingerprinting of the Impact of Acid Mine Drainage After 50 Years of Chronic Pollution in a Southern Finnish Lake

Acid mine drainage (AMD) is acknowledged to have long-lasting impacts on aquatic environments. Hence, mines have also been detected to pose problems years after closure due to the leaching of toxic drainage initiated by sulfide oxidation. To assess the effects of chronic but relatively low volume acid mine drainage derived from the Haveri copper-gold mine operating between 1938 and 1960 on a freshwater bay in southern Finland, we compared cladoceran assemblages from the pre-mining period with contemporary populations using paleolimnological approaches and multiple sediment cores. The cladoceran community of the pre-mining era differed significantly from the contemporary community of the lake (ANOSIM R = 0.91; p = 0.0001), but closely resembled the contemporary community of a nearby non-polluted reference site. Our results suggest that the differences in species compositions between pre-mining and contemporary samples are most likely caused by eutrophication and not by the AMD impact. Because AMD at our study site is most intense during the spring snowmelt period, cladocerans may avoid seasonal pollution peaks through winter dormancy. Possible pollution peaks resulting from heavy rains during the summer may have negative impacts on the cladoceran community, but such short-term impacts are probably rapidly counteracted by immigration from cleaner areas of the lake.Peer reviewe

Postglacial spatiotemporal peatland initiation and lateral expansion dynamics in North America and northern Europe

Peer reviewe

An expanded calibration model for inferring lakewater and air temperatures from fossil chironomid assemblages in northern Fennoscandia

Chironomid-temperature inference models based on an expanded data set of surface-sediment and limnological data from 53 Subarctic lakes in northern Fennoscandia have been developed using eight different numerical techniques, each based on slightly different underlying statistical models or ecological assumptions. The study sites are mostly small, shallow, bathymetrically simple, oligotrophic lakes, with a pH range from 5.0 to 7.8, a total organic carbon range from 2.5 to 12.6 mg l- 1, a mean July lakewater temperature ranging from 6.1 to 15.4°C, and a mean July air temperature ranging from 8.5 to 14.9°C. A series of redundancy analyses (RDA) identified sediment organic content, maximum lake depth, and lakewater temperature as being the most important explanatory variables. Variance partitioning by partial RDAs further suggested that each of these variables accounted for a significant fraction of variance independent from each other. Different cali bration models were assessed on the basis of their statistical performance, with particular reference to prediction errors and the amount of bias along the temperature gradient. Of the eight calibration models, modern analogue techniques, weighted averaging partial least squares, simple weighted averaging with an‘inverse’ deshrinking regression, and linear partial least squares consistently performed best. These methods can all be used to develop transfer functions for surface-water and air July temperatures with a root mean squared error of predic tion (RMSEP) of about 1.5–1.6°C (water temperature) and 0.8–1.1°C (air temperature), as assessed by leave-one-out cross-validation. The resulting models do, however, have relatively high maximum biases (up to 3.9°C) in the lowest segments of the air and water temperature gradients, highlighting the need for enlarging and expanding the calibration data set to include lower temperatures

Dissolved organic matter concentration, optical parameters and attenuation of solar radiation in high-latitude lakes across three vegetation zones

High-latitude lakes are usually transparent, due to their low productivity and low concentration of dissolved organic matter (DOM), but large variations in lake optical properties can be found within and between regions. We investigated the light regimes in relation to DOM in 18 oligotrophic, high-latitude lakes across mountain birch woodland, shrub tundra and barren tundra in north-west Finnish Lapland. In 12 lakes >1% of photosynthetically active radiation (PAR) reached the lake bottom, while 1% UV-B depth ranged from 0.1 to >12 m. Lakes located in barren tundra had highest transparency, lowest dissolved organic carbon (DOC) concentration and lowest DOM absorption (a440) (mean values: Kd PAR 0.3m–1, DOC 2.1mg l–1, a440 0.4m–1), while lakes in shrub tundra and mountain birch forest were less transparent (DOC 4.7 mg l–1, a440 1.4 m–1). Solar attenuation and lake transparency was best explained by a440. Our survey emphasizes the importance of catchment type on DOM characteristics and lake optics. We predict that even small changes in DOM quality may largely change the UV radiation exposure of lakes while changes in PAR may have smaller biological effects in these shallow lakes that are already illuminated to the bottom. Les lacs en hautes latitudes sont généralement transparents due à de faibles productivité et concentration en matière organique dissoute (MOD). Toutefois, ceux-ci présentent une grande variabilité en propriétés optiques. Nous avons étudié le régime lumineux avec la MOD dans 18 lacs oligotrophes des forêts (bouleau pubescent) et toundras (arbustive et herbacée) du nord-ouest de la Laponie finlandaise. Dans 12 lacs, >1% du rayonnement photosynthétique actif (RPA) a atteint le fond, tandis que le UVB 1% atteint entre 0.1 et >12m. Les lacs de la toundra herbacée avaient les transparences les plus élevées mais des concentrations en carbone organique dissout (COD) et en MOD chromophore (a440) les plus faibles (moyennes: RPA Kd 0,3m–1, COD 2,1mg.l –1, a440 0,4m–1), tandis que ceux de la toundra arbustive et des forêts étaient moins transparents (COD 4,7mg.l–1, a440 1,4m–1). L’atténuation de la radiation solaire et la transparence étaient liées à a440. Notre étude montre l’importance du type de bassin versant pour les caractéristiques de la MOD et l’optique des lacs. Nous prédisons que de faibles changements de la MOD pourront causer des changements dans l’exposition aux UV, mais des changements du RPA pourraient avoir de faibles effets biologiques dans ces lacs déjà illuminés jusqu’au fond