Microalgal biovolume and taxonomic composition along a restoration chronosequence in sandy post-mining soils

This study examined microalgal biovolume and taxonomic composition across a restoration chronosequence in sandy post-mining soils and their relationships with abiotic soil properties. The research was conducted in a single sand pit in Central Europe, representing a case study of a typical regional post-mining environment. Samples were collected in winter, spring, and summer from nine experimental plots representing a 4–43-year chronosequence after mining cessation, and from three control plots where mining did not occur. The microalgal biovolume was higher in recently restored plots and lower in older plots. Although biovolume varied seasonally, seasonal changes in taxonomic composition were limited. Biovolume showed a significant negative correlation with organic matter content in all studied seasons, and a similar pattern was observed for Oscillatoriales and Zygnemales, whereas correlations for other taxa varied among seasons and were not consistently significant. In this study, microalgal characteristics did not provide sufficient information for assessing the restoration of sandy post-mining soils under field conditions. However, the decrease in biovolume along the restoration chronosequence, its negative relationship with organic matter content, and the similar relationships observed for taxa identified in this study suggest directions for further investigation. These findings require verification across multiple post-mining sites.