Browsing by Subject "Virtavedet"

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.