Analysis of Periphyton Features in Post-mining Lakes in Northern Bohemia

Abstract

One possible way of post-mining landscape restoration is hydric recultivation when the mining lakes emerge. Due to the recent growing numbers of post-mining lakes connected with coal mine suppression, a better understanding of the post-mining lake´s ecosystem is needed. The presented dissertation thesis aimed to study periphyton, which is often a predominant component of the littoral zone of post-mining lakes. The work was conducted in the years 2019?2021 in the three oligo- to mesotrophic post-mining Lakes Medard, Most and Milada in Northern Bohemia. Several periphyton characteristics were assessed: biomass per area, nutrient composition, and autotrophic diversity. Since the periphyton of investigated lakes exists under conditions of severe phosphorus (P) limitation, special focus was paid to the ability of periphyton to acquire P from the water column. Results showed that diatoms, Chlorophyta and Cyanobacteria are the main autotrophic groups of periphyton in all investigated lakes. Their contribution was changing with the increasing trophy and age of the lake from the dominance of diatoms in the highly oligotrophic youngest Lake Medard to the co-dominance of diatoms and Chlorophyta in Lakes Most and Milada. A high fraction of diatom species (25%) in the respective watershed (Ohře river) were found exclusively in the studied post-mining lakes. Contradicting our expectations, specific P uptake affinity decreased in the season and was not correlated with lake water phosphorus concentration. We assume that two main processes concerning the limiting nutrient phosphorus exist: 1) phosphorus acquisition from the lake water and 2) phosphorus internal recycling in the periphyton mats. The obtained knowledge can be used for identifying future changes in the lakes as well as for the prediction of the development of other newly developed lakes established during the restoration of post-mining lands.