Diffusive Gradients in Thin Films Can Predict the Toxicity of Metal Mixtures to Two Microalgae: Validation for Environmental Monitoring in Antarctic Marine Conditions.

Anthropogenic contamination in the Antarctic near-shore marine environment is a challenge for environmental managers because of its isolation, high costs associated with monitoring and remediation activities, and the current lack of Antarctic-specific ecotoxicological data. The present study investigated the application of diffusive gradients in thin films (DGT) with a Chelex-100 binding resin for metal contaminant assessment in Antarctic marine conditions. Diffusion coefficients for cadmium (Cd), copper (Cu), nickel (Ni), lead (Pb), and zinc (Zn), determined at 1 °C, ranged between 2.1 and 2.6×10-6  cm2 /s and were up to 32% lower than those derived by theoretical calculations. Competition of metals on the DGT binding resin was observed at subsaturation concentrations, reducing the effective capacity for metal uptake by approximately 60%. The lability of the dissolved (0.45 µm filterable) Cd, Cu, Pb, and Zn metal fraction to DGT was generally >90% and unaffected by the presence of the Antarctic marine microalga Phaeocystis antarctica. Both DGT and dissolved metal concentrations gave equivalent mixture toxicity predictions in independent action and concentration addition models to P. antarctica and Cryothecomonas armigera; that is, predictions using DGT-labile concentrations also showed antagonism to P. antarctica, which agrees with previously determined mixture interactivity. The benefits of DGT over traditional sampling techniques (i.e., discrete water sampling) include lower method detection limits (MDLs), in situ assessment, and time-averaged concentrations which capture pulses of contamination typical of the Antarctic near-shore marine environment. The present study provides MDLs and recommended minimum deployment times to guide field deployments in Antarctica. Environ Toxicol Chem 2019;38:1323-1333. © 2019 SETAC.