Nitrate-N-mediated toxicological responses of Scenedesmus acutus and Daphnia pulex to cadmium, arsenic and their binary mixture (Cd/Asmix) at environmentally relevant concentrations

[摘要] Several biomarkers used for ecological risk assessment have been established for single contaminant toxicity, many of which are less predictive of the influence of media and/or dietary nutrients on toxicity outcomes of contaminant mixtures. In this study, we investigate toxicological responses and life traits of Scenedesmus acutus and Daphnia pulex to heavy metals (cadmium-Cd, arsenic-As, binary mixture-Cd/As-mix) in media and diets with varied nutrient (nitrate-N) conditions (low-LN, median-MN, optimum - COMBO). Results showed that nitrate-N-mediated metal inhibitory effects on growth and productivity of primary producer (S. acutus) were significantly interactive (p < 0.05; effect size, eta(2) <= 56 %). Cadmium toxicities (Cd-IC50 s) in S. acutus were 1.2 x , 5.3 x , and 4.3 x As-IC(50)s in LN, MN and COMBO media, respectively, while mixture (Cd/As-mix) toxicities were synergistic in MN medium and partial additivity in COMBO and LN media. Nitrate-N and metal exposure effects on S. acutus nutrient stoichiometry, metal uptake and bioaccumulation were significantly interactive (p < 0.05, eta(2)<= 100 %). Moreover, survival of primary consumer (D. pulex) was significantly impaired by single and mixed dietary-metal exposures with greater effect under LN condition coupled with significant interactive effects on reproductive capacity (p < 0.05, eta(2)<= 21.2 %) but not on swimming activity. We recommend that nitrate-N-mediated metal exposure effects/toxicity in bioindicator species should be considered during ecological risk assessments.

[发布日期] 2020-12-05

[关键词] Nitrogen availability;Heavy metals;Contaminant mixtures;Interactive effects;Ecotoxicological risk assessment