Browsing by Author "Tupola, Vilja"

Distribution and abundance of organisms are in constant interaction with spatial and temporal factors. In addition to local environmental variables, micro-organisms are also affected by large-scale regional and historical factors, such as macro-organisms. Diatoms occur diversely in aquatic ecosystems and react sensitively to physical, chemical and biotic variables of water, thus they are well suited indicators of environmental conditions and change. Diatoms play an important role as primary producers and as participants of the cycle of materials. Particularly, streams in the northern and alpine regions are more sensitive to the effects of climate change than other locations. Especially in Iceland, global warming can lead to a significant increase of agriculture that increases the amount of nutrients received by streams. An elevation gradient represents how organisms react to environmental change in a small geographical area. This study examines the effects of environmental factors to diatom species richness and community composition in the arctic-alpine streams in Iceland. In this research, environmental variables include physical and chemical characteristics of water, elevation above sea level and channel and sample stone measurements. As a special topic, the study examines how the effects of elevation change affect to diatoms. This phenomenon has had minor studies in the past. In addition, the study examines the effects of geographical location on community composition, species richness and environmental conditions by comparing to this data and the data collected from Northern Finland and Norway. The data of this study was collected in August 2016 in Iceland from streams in areas with strong elevation gradients. There were 45 sample sites in total. The interdependencies of the environmental variables and relation between the environmental variables and the species richness were examined using Spearman’s order correlation coefficient and scatter patterns. The variation of species richness was examined with generalized linear models (GLM). The variation of community composition was analyzed with redundancy analysis (RDA). The data of Iceland was compared to the data of North Fennoscandia with non-metric multidimensional scaling (NMDS), principal component analysis (PCA) and analysis of similarities (ANOSIM). The species richness was best explained by current velocity, pH of water, channel depth, conductivity and elevation. The community composition was most affected by total phosphorus, pH, channel depth and temperature. The local species richness in Iceland and North Fennoscandia were quite similar, but the species composition differed mostly between the regions. There were also differences in environmental variables between the regions, but less than the case of species. The local environmental variables affected the species richness and the community composition more than elevation. The most significant factor to determine the diatom communities was pH of water. An isolation of Iceland can affect the regional differences of community composition despite the good dispersal ability of diatoms. However, the environmental variables differed regionally, so communities can occur in both areas, but local environmental variables determine the success of the species in each habitat.