Responses of diatom composition and teratological forms to environmental pollution in a post-mining lake (SW Poland)

Various types of environmental stressors, such as heavy metals, lignite residues, or extremely low water pH, cause the formation of teratological forms of diatoms during the reproductive cycle. The damage mainly includes an abnormal diatom valve outline, changes in the striation pattern, anomalies in the raphe line/sternum, reduction in the cell size, metabolism alterations, or combined deformities. Diatom remains with such morphological deformities occur in the sediments of post-mining lake ŁK-46 (SW Poland). This lake was formed by excavation after the end of lignite exploitation in the mid-1960s. The percentage of teratological valves in the studied lake ranged from 12 to 33% of the relative abundance. The majority of abnormal diatoms have been observed in species of Eunotia. The reconstruction of the diatom-inferred pH (DI-pH), together with the concentration of heavy metals in the sediments and contemporary measurements of the water pH, indicates that the lake was contaminated to varying degrees and was acidic from the beginning of lake creation until today. The lake is located in an area of acid mine drainage (AMD), and in its vicinity, there are overburden heaps containing lignite residues, which are eroded and supplied to the lake, constantly acidifying the water. In the youngest sediments, the concentration of heavy metals increased, while the percentage of abnormal diatoms decreased. Determining which factor, i.e., extremely low water pH and the presence of lignite or heavy metals, was responsible for the formation or reduction of teratogenic forms of diatoms is very difficult.