Anoxia threatens inland waters worldwide. Once it has occurred in a lake, the lack of oxygen even sets in motion a downward spiral that accelerates with increasing global warming. This is indicated by the results of an international study involving researchers of TU Bergakademie Freiberg, which were published in the scientific journal "Global Change Biology". According to the study, lakes that were once affected by a lack of oxygen in deep water are affected again the following year. As a result, the living conditions for fish and invertebrates continue to deteriorate, greenhouse gases are increasingly released and nutrient cycles are intensified.