Benthic diatom communities in high-Arctic streams across a water chemistry gradient in Zackenberg Valley, Northeast Greenland

Arctic streams are highly sensitive to climate change and their biological communities are subjected to considerable changes. Benthic diatom communities are an important basal resource for higher trophic levels in these oligotrophic streams. However, our knowledge on how they respond to stream physicochemical characteristics in the Arctic is limited. The objective of this study was to describe diatom communities’ characteristics and assess how they are related to physicochemical parameters in 15 stream reaches in Northeast Greenland. Overall, we found 36 species across the streams from which Planothidium frequentissimum was the most abundant followed by Nitzschia palea. Based on physicochemical variables, including water nitrogen concentration, dissolved organic carbon concentrations and conductivity, the sampling sites were separated into three stream types: headwater, valley and glacial and snowpack runoff streams. Trait analyses showed that the majority of the species belonged to the ‘macro’ cell size category, strongly correlated with higher concentration of nitrogen. Diatom diversity was negatively affected by water velocity with glacial and snowpack runoff streams to be characterized by the lower number of species. Very small variation was explained solely by the physicochemical variables indicating that the distribution of diatom communities is influenced significantly by catchment characteristics. Overall, our study underlines the need for more comprehensive assessments in order to understand how diatom community composition is controlled by larger scale environmental variables in Arctic streams.