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

Abstract

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

New insights into osmobiosis and chemobiosis in tardigrades

“…Currently very few toxicological studies have been conducted within tardigrades (Sobczyk et al, 2015;Hygum et al, 2017). However, recent investigations on metal tolerance, supports the assumption that tardigrades and rotifers have the ability to enter a quiescent state in response to high toxicant concentrations (Hygum et al, 2017;McCarthy et al, 2022;Brown et al, 2023).…”

“…The latter provides evidence of chemobiosis, i.e. , cryptobiosis induced by environmental toxicants ( Møbjerg et al, 2011 ; Hygum et al, 2017 ; Møbjerg and Neves, 2021 ; McCarthy et al, 2022 ; Brown et al, 2023 ). We discuss our data in relation to earlier and more contemporary studies on cryptobiosis in tardigrades and stress that osmobiosis should be defined as a state of cryptobiosis induced by high external osmolyte concentrations.…”

Population growth of two limno-terrestrial Antarctic microinvertebrates in different aqueous soil media

“…However, there is little evidence in the literature to support this; ultrapure water was successfully used as a media in toxicity tests with the Antarctic bdelloid rotifers, Philodina sp. (McCarthy et al 2022 ) and Adineta editae (Brown et al 2023 ). Additionally, low calcium has been found to be beneficial to the reproductive output of the monogonont rotifer Mytilina brevispina (Sincock 1976 ), and phosphorus deficiency in an algae food source was found to have no impact on population growth of the rotifer of Brachionus plicatilis (Matsui et al 2020 ).…”