Browsing by Subject "subarctic"
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(2021)Aims of this study. Previous studies have shown cyanobacterial dominance and harmful cyanobacterial blooms to increase due to recent climate warming. The increase of aggressively blooming species and toxin-producing strains of cyanobacteria has been predicted to further increase in the future. However, information on the response of cyanobacteria communities to environmental forcing in the Arctic region – which is experiencing warming at over twice the rate compared to the global average – has been insufficient. Thus, it is crucial to study how algal and cyanobacterial communities have developed after industrialization to better understand and predict future trends of subarctic algal communities as well as changes within cyanobacteria communities experiencing environmental forcing. This study aims to provide information on the effect of recent climate warming and lake browning on algal communities in subarctic lakes, with a special focus on cyanobacteria and cyanotoxins. Materials and methods. Modern and historical primary producer group abundances of 23 subarctic lakes located on an ideal temperature and vegetation gradient were studied using sedimentary algal pigments as a proxy. The top-bottom method was used to study both changes within algal communities during the last ca. 150 years and the broader trends in algal communities of subarctic lakes. Pigment data was analyzed together with environmental data using ordination analyses (principal component analysis (PCA) and redundancy analysis (RDA)) as well as other statistical analyses in order to determine possible trends of change and to reveal the environmental variables that have the strongest impact on cyanobacterial abundance. Results and conclusions. Algal communities have changed during the last ca. 150 years and show a general trend of increased primary production as well as lake browning in the spruce, pine and birch (SPB) vegetation zone. Siliceous algae generally dominate modern algal communities, and relative abundances of cyanobacteria have declined throughout the vegetation gradient. Within the Barren (Ba)- and mountain birch woodland (MBW) vegetation zones, cyanobacteria communities show a marked decline in the abundance of assumed benthic species based on pigment data, and low abundances of planktic picocyanobacteria. However, due to climate warming and lake browning, abundances of cyanobacteria have increased in several sites within the SPB vegetation zone and are suspected to indicate an increase of harmful planktic species. The most significant environmental variables controlling the abundance of cyanobacteria were total phosphorus, temperature and the amount of organic matter. The results highlight the urgent need to mitigate climate warming in order to preserve the unique biota and characteristics of Arctic and subarctic lake ecosystems, and to prevent the possible harmful increase of cyanotoxins in these sensitive ecosystems.
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(2021)Aims of this study. Previous studies have shown cyanobacterial dominance and harmful cyanobacterial blooms to increase due to recent climate warming. The increase of aggressively blooming species and toxin-producing strains of cyanobacteria has been predicted to further increase in the future. However, information on the response of cyanobacteria communities to environmental forcing in the Arctic region – which is experiencing warming at over twice the rate compared to the global average – has been insufficient. Thus, it is crucial to study how algal and cyanobacterial communities have developed after industrialization to better understand and predict future trends of subarctic algal communities as well as changes within cyanobacteria communities experiencing environmental forcing. This study aims to provide information on the effect of recent climate warming and lake browning on algal communities in subarctic lakes, with a special focus on cyanobacteria and cyanotoxins. Materials and methods. Modern and historical primary producer group abundances of 23 subarctic lakes located on an ideal temperature and vegetation gradient were studied using sedimentary algal pigments as a proxy. The top-bottom method was used to study both changes within algal communities during the last ca. 150 years and the broader trends in algal communities of subarctic lakes. Pigment data was analyzed together with environmental data using ordination analyses (principal component analysis (PCA) and redundancy analysis (RDA)) as well as other statistical analyses in order to determine possible trends of change and to reveal the environmental variables that have the strongest impact on cyanobacterial abundance. Results and conclusions. Algal communities have changed during the last ca. 150 years and show a general trend of increased primary production as well as lake browning in the spruce, pine and birch (SPB) vegetation zone. Siliceous algae generally dominate modern algal communities, and relative abundances of cyanobacteria have declined throughout the vegetation gradient. Within the Barren (Ba)- and mountain birch woodland (MBW) vegetation zones, cyanobacteria communities show a marked decline in the abundance of assumed benthic species based on pigment data, and low abundances of planktic picocyanobacteria. However, due to climate warming and lake browning, abundances of cyanobacteria have increased in several sites within the SPB vegetation zone and are suspected to indicate an increase of harmful planktic species. The most significant environmental variables controlling the abundance of cyanobacteria were total phosphorus, temperature and the amount of organic matter. The results highlight the urgent need to mitigate climate warming in order to preserve the unique biota and characteristics of Arctic and subarctic lake ecosystems, and to prevent the possible harmful increase of cyanotoxins in these sensitive ecosystems.
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(2020)Global warming caused by the warming effect of greenhouse gases (GHGs) induces permafrost thaw, which could alter Arctic ecosystems from prominent carbon sinks to potential sources of GHG emissions when polar microorganisms become metabolically more active and have access to carbon compounds that were previously largely unavailable. Polar microbes can have significant contributions to the growing emissions of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) and therefore, studies on their metabolism are important. The aim of my study was to investigate polar microbial community composition and diversity as well as functional potential that was related to GHG-cycling in a subarctic environment with genome-resolved metagenomics. Soil cores were collected at the Rásttigáisá fell that is located in Northern Norway. After DNA extraction, ten mineral soil samples were sequenced. Metagenome-assembled genomes (MAGs) were reconstructed using either the combination of human-guided binning and automatic binning or human-guided binning only. Taxonomy was assigned to the MAGs and the functional potential of the MAGs was determined. I recovered dozens of good-quality MAGs. Notably, the MAGs from the mostly unknown phyla Dormibacterota (formerly candidate phylum AD3) and Eremiobacterota (formerly candidate phylum WPS-2) were reconstructed. There were MAGs from the following bacterial phyla as well: Acidobacteriota, Actinobacteriota, Chloroflexota, Gemmatimonadota, Proteobacteria and Verrucomicrobiota. In addition to the bacterial MAGs, MAGs from the group of ammonia-oxidizing archaea were recovered. Most of the MAGs belonged to poorly studied phylogenetic groups and consequently, novel functional potential was discovered in many groups of microorganisms. The following metabolic pathways were observed: CO2 fixation via the Calvin cycle and possibly via a modified version of 3-hydroxypropionate/4-hydroxybutyrate cycle; carbon monoxide oxidation to CO2; CH4 oxidation and subsequent carbon assimilation via serine pathway; urea, ammonia and nitrite oxidation; incomplete denitrification as well as dissimilatory nitrate reduction to ammonium. My study demonstrates how genome-resolved metagenomics provides a valuable overview of the microbial community and its functional potential.
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(2021)Geodiversity, the natural abiotic variety of the Earth’s surface, is an essential part of natural diversity and plays an important role in providing the abiotic ecosystem services that all life depends on. Geodiversity is increasingly threatened by human activities and climate change, and consequently there is a growing importance of including geodiversity in decision-making. However, there is still a lack of studies assessing the spatial variation and key drivers of geodiversity, especially in high latitude and altitude areas, and this study, therefore, aims to contribute to an improved understanding. In this study, the geodiversity of a subarctic mountainous area in Northern Norway was mapped using remotely sensed data and applying a grid-based approach. The spatial variation of geodiversity was assessed using five different measures, and the relationships between geodiversity and several topographical parameters were analysed using correlation analysis (Spearman’s rank correlation, RS) as well as both univariate and multivariate linear regression. The vertical variation of geodiversity was also examined to analyse the variation of geodiversity along altitudinal gradients. A total of 54 geodiversity elements were observed in the study area and the number of elements per grid cell varied from 7 to 36. Four of the geodiversity measures correlated strongly, resulting in relatively similar spatial patterns of diversity. Higher values tended to follow the valley systems and cluster in the vicinity of rivers and larger streams. Topographically diverse grid cells, containing both steeper slopes and smoother areas, also contained a higher diversity. Low diversity occurred mainly on the highest elevations as well as on the steepest slopes. The majority of the univariate relationships between the measures of geodiversity and the topographical parameters were statistically significant, although the correlations generally were relatively weak. The regression models further confirmed the relationship between topography and geodiversity, and revealed various statistically significant relationships, as well as the presence of both linear and unimodal relationships. Higher geodiversity generally occurred in topographically heterogeneous landscapes, as well as in the vicinity of rivers and larger streams, where both erosion and accumulation processes are prominent, leading to a great variety of geomorphological elements and soil deposits. The summits and slopes of the mountain massifs, on the other hand, displayed a lower geodiversity. In these areas, erosion is significant, but accumulation processes are lacking. Furthermore, the hydrological diversity is generally low there. The vertical patterns of geodiversity were related to the spatial patterns since total geodiversity decreased steadily as mean elevation rose above 600 m a.s.l. The influence of topography on geodiversity patterns could also be seen in the statistically significant relationships between several topographical parameters and the geodiversity measures. There was, however, some variation in the strength of the correlations, and the weaker relationships can partly be explained by the contradictory effect of slope angle and elevation on geodiversity. These patterns were further confirmed by the fact that the regression models revealed not only linear, but also unimodal relationships between the topographical parameters and geodiversity. Although topography seems to have an important effect on all geodiversity measures, there is some variation in which topographic parameters are the most important for the different measures. To conclude, this study of a northern high latitude mountainous area shows that high geodiversity occurs in the vicinity of rivers and larger streams, as well as in landscapes with a varied relief. Topography has a statistically significant influence on geodiversity, although the magnitude and direction of the effect varies between the elements of geodiversity. To facilitate the incorporation of geodiversity in education, land use planning, resource management and nature conservation, more research is still required about the patterns and drivers of geodiversity.
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(2019)Soil microbial communities have a critical role in the biogeochemical processes on Earth, but their response to the ongoing climate change is poorly understood. Arctic permafrost harbors approximately 50% of Earth’s below ground carbon, and warmer climate leads to increased rate of microbial decomposition of soil organic matter in polar regions. Without a comprehensive understanding of the soil microbial ecology, the overall impact of climate change to nutrient cycles and greenhouse gas emissions is difficult to predict. My aim was to improve the knowledge of active microbes and their energy sources in subarctic soil. I studied the activity and functions of soil microbial communities by applying metatranscriptomics to soils along a natural climate gradient in subarctic Kilpisjärvi, northwestern Finland. The gradient represents the possible soil conditions, that microbial communities live in as the climate changes. Additionally, I studied the relationship of microbial activity and various environmental factors, including pH and soil organic matter. Results of the thesis showed that the active microbial communities in subarctic soils are diverse taxonomically and by their energy metabolism, and that pH, soil organic matter content and moisture are the main drivers of soil microbial activity and functions.
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(2019)Soil microbial communities have a critical role in the biogeochemical processes on Earth, but their response to the ongoing climate change is poorly understood. Arctic permafrost harbors approximately 50% of Earth’s below ground carbon, and warmer climate leads to increased rate of microbial decomposition of soil organic matter in polar regions. Without a comprehensive understanding of the soil microbial ecology, the overall impact of climate change to nutrient cycles and greenhouse gas emissions is difficult to predict. My aim was to improve the knowledge of active microbes and their energy sources in subarctic soil. I studied the activity and functions of soil microbial communities by applying metatranscriptomics to soils along a natural climate gradient in subarctic Kilpisjärvi, northwestern Finland. The gradient represents the possible soil conditions, that microbial communities live in as the climate changes. Additionally, I studied the relationship of microbial activity and various environmental factors, including pH and soil organic matter. Results of the thesis showed that the active microbial communities in subarctic soils are diverse taxonomically and by their energy metabolism, and that pH, soil organic matter content and moisture are the main drivers of soil microbial activity and functions.
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(2022)Nitrous oxide (N₂O) is a powerful greenhouse gas, and its global warming potential is almost 300 times more compared to carbon dioxide. In the soil ecosystem, N₂O is mainly released into the atmosphere in the microbiological process, denitrification. Subarctic tundra soils are important sources of N₂O and due to global warming, N₂O can be released an increasing amount from these soils in the future. Snow cover and ice layers influence to production of greenhouse gases during winter. In this master’s thesis, active microbial communities and their functional genes were studied from subarctic tundra soils across the five different vegetation types in northern Finland in early April. Additionally, various environmental factors (pH, soil temperature, soil organic matter, soil water content, and snow depth) and gas fluxes of nitrous oxide, methane, and carbon dioxide were studied together with metatranscriptomic data. The study focuses on the genes involved in denitrification, as it is the main process of releasing N₂O. This study showed that microbial activity was notable already in early April and indicated that microorganisms stayed active in these subarctic soils in winter and can continue producing greenhouse gases throughout the year. Kilpisjärvi tundra soils are complex systems, and various environmental factors shaped the abundance and diversity of active denitrifiers, their functional genes, and the production of N₂O. Transcripts of genes involved in denitrification were active and N₂O fluxes ranged from -4 to 21 μg m-2 d-1. Overall production of N₂O from these tundra soils was small, yet evident, and the soils can be notable sources of N₂O in winter.
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(2022)Nitrous oxide (N₂O) is a powerful greenhouse gas, and its global warming potential is almost 300 times more compared to carbon dioxide. In the soil ecosystem, N₂O is mainly released into the atmosphere in the microbiological process, denitrification. Subarctic tundra soils are important sources of N₂O and due to global warming, N₂O can be released an increasing amount from these soils in the future. Snow cover and ice layers influence to production of greenhouse gases during winter. In this master’s thesis, active microbial communities and their functional genes were studied from subarctic tundra soils across the five different vegetation types in northern Finland in early April. Additionally, various environmental factors (pH, soil temperature, soil organic matter, soil water content, and snow depth) and gas fluxes of nitrous oxide, methane, and carbon dioxide were studied together with metatranscriptomic data. The study focuses on the genes involved in denitrification, as it is the main process of releasing N₂O. This study showed that microbial activity was notable already in early April and indicated that microorganisms stayed active in these subarctic soils in winter and can continue producing greenhouse gases throughout the year. Kilpisjärvi tundra soils are complex systems, and various environmental factors shaped the abundance and diversity of active denitrifiers, their functional genes, and the production of N₂O. Transcripts of genes involved in denitrification were active and N₂O fluxes ranged from -4 to 21 μg m-2 d-1. Overall production of N₂O from these tundra soils was small, yet evident, and the soils can be notable sources of N₂O in winter.
Now showing items 1-8 of 8