Conditions for development of anthropogenic meromictic reservoirs in the workings of crystalline rocks (based on the examples of the quarries of the Zulovska pahorkatina, NE Czech Republic)

Abstract

There are numerous anthropogenic water reservoirs in the vicinity of the Z ˇ ulovska´ pahorkatina (northern Czech Republic). The vast majority of them have developed as a result of the flooding of the abandoned quarries of crystalline rocks (granites or granodiorites). The surface area of these water bodies is small and is \6000 m2. These are, however, very deep reservoirs of up to 25 m. Permanent water stratification has been recorded in some of them; these are meromictic reservoirs. The development of the phenomenon of meromixis in the reservoirs that were studied was conditioned by the supply of organic matter from the catchment. The biochemical process of organic matter decomposition led to the release of ions, mainly NH4 ?. The accumulation of dissolved substances in the benthic zone initiated the meromixis phenomenon. Therefore, the water bodies that were tested can be classified as reservoirs of the biogenic type of meromixis. This article presents the stages of the evolution of a holomictic reservoir into a meromictic one. Three water bodies in which meromixis was recorded were selected for the study. The control object was an abandoned quarry reservoir with no meromixis.