Browsing by Author "Granqvist, Sonja"

Substratum and environmental variables influence benthic algal species richness and community composition. Benthic habitats form complex connections within and between communities leading to unique water ecosystems. In order to better understand substratum relationships and the effects of environmental covariates towards microorganisms, this study focused on benthic diatoms in subarctic mountain ponds living in different substrata. Moreover, methodological choices are important for field survey in freshwater environments and thus in this study, we also compared sponge and brush sampling techniques to examine possible differences in benthic diatom species richness and community composition. We sampled 23 subarctic ponds between July and August 2022 in northern Fennoscandia. The samples were taken from stones and sediment. To analyse the differences between species richness for substrata and methods, we used paired Wilcoxon signed-rank test and paired t-test. In order to find out the most significant environmental variables influencing diatom species richness, we used generalized linear models (GLM). Differences in diatom community compositions were analysed using non-metric multidimensional scaling (NMDS), analysis of similarities (ANOSIM), and Jaccard similarity index. Finally in order to visualise the variation in community composition between stone and sediment samples explained by environmental variables, a redundancy analysis (RDA) was used. Benthic diatom species richness significantly differed between rock and sediment substrata where sediment was the most species rich substratum. Local environmental variables were influential towards diatom species richness, where water pH was the major determinant for both substrata. Diatom community composition did not differ significantly between rock and sediment substrata but was defined by environmental variables such as pond surface area and water pH having a strong influence on both substrata. No significant differences were found between sampling methods in terms of diatom species richness or community composition. Our results support the theory that sediment substratum contains the highest diatom species richness. Furthermore, the study highlights the importance of water pH on benthic diatoms regardless of substratum, supporting diatom reliability as bioindicators for water pH.