Toxic effects of metals on two euryhaline ciliate species adapted to variable salinities

Brackish waters having salinity lower than seawater but higher than fresh water are of high importance for mankind. They serve as waterways, sources of sea food, sand or gravel, and play role in number of biogeochemical cycles including nutrients. However, human activities lead to serious pollution in these ecosystems affecting aquatic biota, migrating birds and others. The available aquatic ecotoxicity assays use either organisms from freshwaters or species from marine waters. Tools to assess the toxic effects of chemicals under the intermediate salinities are thus limited. The present study developed a 72-h growth inhibition assay in 48-well microplates using two euryhaline ciliates Paramecium dubosqui and Paramecium nephridiatum, each adapted to two different salinities: 0.5‰ and 5‰. The toxicities of metals under variable salinity conditions differed (HgCl