Effects of Deicing Salt in Protected Areas: Water Quality Monitoring in the River Basin with the Occurrence of a Rare Pearl Mussel

Abstract

The effects of deicing salt on water ecosystems have been studied in the Šumava National Park and Protected Landscape Area. A pilot study was conducted in the Upper Vltava River basin, a habitat of the strictly protected pearl mussel. Dataloggers were used to investigate conductivity, often recommended as an important indicator of water quality. In this pilot project two pairs of dataloggers were installed in two streams crossed by the roads with different road maintenance regime. The first site was established in location, where deicing salt has not been allowed at all, but preliminary results of soil and vegetation monitoring indicated some impacts of deicing salts in this location. The records from dataloggers confirmed this, but conductivity was not so high at the second site. The second site was established on a priority road, permanently maintained by deicing salt. In this site, we often recorded conductivity higher than 75 μS/cm, water quality limit for suitable habitats of the strictly protected pearl mussel. High conductivity may negatively affect viability of the population. From a methodological point of view, there are two main outputs of this pilot project. (1) We found that dataloggers can be frozen and out of records in shallow water during longer frost period. (2) We also confirmed hypotheses that not all ions are transported rapidly through the soil and groundwater. Conductivity was lower during winter and increased with snow melting. During vegetation season dataloggers recorded decrease of conductivity after heavy rains or longer rain period. Conductivity increased again in dry period. We conclude that the dataloggers improve our knowledge of impact of deicing salt in water ecosystems and offer relevant arguments for EIA in the area of high conservation value. Of course more statistical analyses are necessary; more detail information about annual differences in weather conditions and amount of deicing salt applied in different locations (not only a total amount of salt for a whole road) could help to interpret our data.