Relationships between freshwater sedimentary diatoms and environmental variables in Subarctic Icelandic lakes

Abstract

The distribution patterns of surface sediment diatom assemblages from 49 lakes were used to explore the relationship between limnological variables and diatom assemblages as well as to assess an ecological classifi ca- tion system as a tool for the management and conservation of Icelandic freshwaters. Lakes were limnologically diverse ranging from deep, oligotrophic, ionically dilute lakes, to shallow lakes with a wide range of nutrient and ionic contents. Physical conditions (depth, surface area, surface water temperature) and nutrient and ion concentra- tions differed signifi cantly among ecological lake categories (i.e., plateau, spring-fed, direct-runoff, valley, glacial, and coastal lakes) (ANOVA, p 20 % in all but 4 of the lakes, most likely due to the generally cold lake water conditions in this subarctic region. Variation in diatom distributions was best explained by the combination of mean depth (infl uencing littoral versus planktonic habitats), surface water temperature, specifi c conductivity, alkalinity, total organic carbon, total nitrogen and SiO2 in a canonical correspondence analysis (CCA). However, these variables did not explain distribution patterns amongst small benthic Fragilaria taxa, although some weak relationships between some taxa and these variables were evident. Distinct diatom assemblages and limnological properties among ecological lake categories support the classifi cation of Icelandic freshwaters based on major topographic, geological and hydrological characteristics. More detailed inclusion of lake depth along with lake basin form, as well as more refi ned categories of lake water origin and topographical positioning to better approximate regional climatic conditions, may improve the ecological classifi cation of Icelandic freshwaters for conservation and management practices.