High Sensitivity of the Antarctic Rotifer Adineta editae to Metals and Ecological Relevance in Contaminated Site Risk Assessments.

Anthropogenic activities in Antarctica have led to contamination of terrestrial sites, and soils in ice-free areas have elevated concentrations of metals, particularly around current and historic research stations. Effective management of Antarctic contaminated sites depends on the assessment of risks to a representative range of native terrestrial species. Bdelloid rotifers are an abundant and biodiverse component of Antarctic limnoterrestrial communities and play a key role in nutrient cycling in Antarctic ecosystems. The present study investigates the toxicity of five metals (cadmium, copper, nickel, lead, and zinc) to the endemic bdelloid rotifer Adineta editae, both singly and in metal mixtures. Based on the concentrations tested, zinc was the most toxic metal to survival with a 7-day median lethal concentration (LC50) of 344 µg Zn/L, followed by cadmium with a 7-day LC50 of 1542 µg Cd/L. Rotifers showed high sensitivity using cryptobiosis (chemobiosis) as a sublethal behavioral endpoint. Chemobiosis was triggered in A. editae at low metal concentrations (e.g., 6 µg/L Pb) and is likely a protective mechanism and survival strategy to minimize exposure to stressful conditions. Lead and copper were most toxic to rotifer behavior, with 4-day median effect concentrations (EC50s) of 18 and 27 µg/L, respectively, followed by zinc and cadmium (4-day EC50 values of 52 and 245 µg/L, respectively). The response of rotifers to the metal mixtures was antagonistic, with less toxicity observed than was predicted by the model developed from the single-metal exposure data. The present study provides evidence that this bdelloid rotifer represents a relatively sensitive microinvertebrate species to metals and is recommended for use in contaminant risk assessments in Antarctica. Environ Toxicol Chem 2023;42:1409-1419. © 2023 SETAC.