Diatom distribution in an alpine basin (central China) in relation to environmental factors and substrata

This study examines the habitat preferences of diatom species for bogs, ponds and streams, and explores the effects of environmental variables and substrata on diatom distribution in an alpine basin (Dajiuhu Basin, central China). Ponds and streams were characterized by high pH and high ionic strength, while bogs were acidic and heavy metal-rich habitats. Diatom samples of the epiphyton (attached to Sphagnum), the epipelon (associated with the mud) and the epilithon (attached to stones) were collected from bogs, ponds and streams, respectively. Diatom assemblages in bogs were characterized by acid-tolerant species, such as Eunotia paludosa, Eunotia seminulum and Frustulia rhomboides. In streams, the indicator species preferred circumneutral or alkaline conditions, and included Achnanthidium minutissimum, Nitzschia perminuta and Reimeria sinuata. The characteristic taxa in ponds included Achnanthidium catenatum, Aulacoseira ambigua and Discostella pseudostelligera. Canonical correspondence analysis (CCA) revealed that variations in diatom communities were significantly correlated with two environmental factors (i.e., concentrations of Si and ) and two substratum types (i.e., Sphagnum and stones). Substrata were found to influence diatom composition, probably through mediating the availability of microhabitats, moisture and nutrients. Our results point out the importance of substrata for diatom-based environmental monitoring. This study provides baseline information on diatom communities in the Dajiuhu Basin, for future comparisons, highlighting the utility of diatoms for monitoring environmental change in alpine landscapes.