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Browsing by Subject "BenthoTorch"

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  • Diatom species richness and community composition along an elevational gradient in subarctic ponds 
    Heikkinen, Janne (2020)
    Subarctic ponds are important habitats for many freshwater species. The recent increase in global temperatures have stressed on the study of these habitats as rising water temperatures may have severe consequences to these cold and harsh ecosystems. Despite its importance, this topic has been largely overlooked in scientific research. Diatoms are microscopic, single-celled benthic algae, which are important indicators for environmental quality. Elevation is one of the main environmental variables controlling the composition and richness of diatom species as it shapes communities through several environmental variables such as temperature and water chemistry. The aim of this thesis was to illustrate the variability in diatom species richness and community composition along an elevational gradient in Kilpisjärvi and reveal the most important environmental drivers. As an additional focus, the applicability of the BenthoTorch sampling device was tested in measuring benthic algae biomass. Field and laboratory measurements were done using universal standards. Statistical analyses included multiple univariate and multivariate data analysis techniques. It was found that water pH, aluminium concentration and air temperature explained the variation in species richness and community composition the most. Elevation had only a secondary, non-significant role in shaping the diatom communities in subarctic ponds. Nearby sites showed similar compositions in terms of water chemistry and diatom communities. Biotope characterisation did not provide any further insight into the differences or similarities of diatom community composition or species richness. There were some differences in how genera responded to environmental variables. The centre of distributional range of many taxa was below the mid-point of the elevational gradient but species often occupied the whole elevational gradient. Rare taxa appeared at the ends of the elevational spectrum. The amount of singleton taxa was high (25.8%) and can be expected to increase with climate change. The BenthoTorch did provide reasonable results for benthic algae in the subarctic when compared to previous literature, but further research is required to grasp its full potential. More examination into the relationship between explanatory variables can be suggested (e.g. total phosphorus and ion balance) to gain better understanding on the changes in diatom species richness and community composition along elevational gradients.
  • Leväbiomassan vaihtelu Etelä-Suomen virtavesissä 
    Sirviö, Markus (2022)
    Diatoms, green algae, and cyanobacteria react fast to changing environmental conditions. Algae are important primary producers in stream ecosystems, thus changes in periphyton can influence the whole stream ecosystem. There have not been many studies where algae biomass variation has been explained with a large water chemistry data. Furthermore, there is lack of studies where metal concentrations in the water are near to natural concentration levels. In this master’s thesis I examine how environmental variables affect the changes in algae biomass. Furthermore, the aim of this study is to examine do diatoms, green algae and cyanobacteria have different responses to environmental variables. Competition between three algae biomass groups is also researched. In this study research points were classified to three land use types. The aim of the classification was to enable variation as much as possible in shading and water chemistry variables in the study area. Eventually 51 research points were selected. Algae biomass was measured with BenthoTorch. Total phosphorus, total nitrogen, anions, cations, solid matter, dissolved matter and dissolved metals were measured in laboratory. Total biomass’ and algae groups’ response shapes where analyzed with GAM. Furthermore, competition between different algae groups were studied with Spearman’s correlation. The average total algae biomass was 2.94 μg cm-2 in the study area and diatoms were the most dominant group. Surprisingly the amounts of light and total phosphorus were sufficient in the study area and had no significant effect on the total algae biomass variation. However, total nitrogen, calcium, zinc, iron, and nickel were significant environmental variables in total biomass model. Total nitrogen, calcium, zinc and nickel where significant environmental variables for explaining diatom biomass variation. Total phosphorus and nitrogen were significant in cyanobacteria’s model and only zinc was significant in green algae’s model. Green algae had a weak but a significant negative correlation with diatoms and cyanobacteria. Total algae biomass growth was notable restricted in study area. The average amount of biomass matched a biomass volume in an oligotrophic stream. There were enough of light and total phosphorous in the study area, thus they had no significant effect on algae biomass. At high total nitrogen concentration levels biomass growth was inhibited. In addition, iron and nickel had a significant negative effect on total biomass. Zinc was an important mineral for algae biomass growth, specially to diatoms and green algae. Strong competition on resources did not occur between the algae groups. Negative correlations between algae groups where most likely explained with different responses to iron, nickel, and calcium. There is need for more studies to explain algae biomass in different natural stream ecosystems. For understanding better how different concentrations change algae biomass, more variation on environmental variables is needed. Furthermore, water hydrology and grazing should be measured. In addition, research on how water chemistry changes affect species composition in periphyton is recommended.

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