The effects of sample storage duration on tardigrade density and community composition in moss samples

In studies on micrometazoans, sample storage and processing methods are mostly decided based on sample quality (e.g., substrate type and moisture level), and the choice of methods may affect the reliability of the data. However, these methods are poorly studied and rarely reported in detail. Our aim was to determine the methodological compromise between efficiency and reliability required for large-scale quantitative meiofaunal ecological studies. Specifically, we tested whether storage duration (necessary for large number of samples) affects the density or community composition of tardigrades in moss samples. We focus on a largely unexplored limnoterrestrial ecosystem – boreal peatlands, where moss moisture levels are naturally variable across different microhabitats and moss species. We collected seven moss samples from a peatland in Central Finland, kept them in a refrigerator and extracted tardigrades using the Baermann wet funnel at 1, 24, 48 and 96 h post sampling. We found a significant decrease in tardigrade density (32 % on average), but no changes in community composition, after the first 24 h of storage. Based on these results, we recommend that samples collected from wet limnoterrestrial habitats should be processed within 24 h to ensure accuracy and comparability of large-scale quantitative data on tardigrade ecology.