The gravel pit lakes' water quality, their aquatic ecosystem function, and the effects of environmental changes in northern Poland

Water quality is an important factor to determine a development of living organisms, including the presence of amphibians. It this article we compared the water quality of both, natural infield reservoirs in areas with intensive cultivation of cereals and the recently created reservoirs in the gravel pits in Central Pomerania, northern Poland. We tested all the physico-chemical properties that may impact species richness and reproductive success of amphibians. We observed that gravel ponds were better oxygenated, with higher pH and conductivity, and were less fertile in nutrients. In Pomerania, the water reservoirs in gravel pits had better breeding conditions than in-field ponds with higher total nitrogen and total phosphorus concentrations. There are many scientific papers identifying a negative role of sand and gravel mines, including a release of heavy metals from sediments, a high non-metalic minerals concentration, a destruction of native species of vegetation and occurrence of alien species. Therefore, we should be careful in assessing the role of newly emerging reservoirs in sand and gravel mines. The purpose of our research is to show that sand/gravel mines can be used to protect nature and that they can have also a positive impact. Few previous studies indicate that they may be a favorable place for creating new breeding sites for amphibians, which may ultimately help to preserve species in the face of environmental pollution and climate change.