Functionalized silver nanoparticles depress aerobic metabolism in the absence of overt toxicity in brackish water killifish, Fundulus heteroclitus.

Engineered nanomaterials (ENMs) tend to precipitate in saline waters so the majority of aquatic toxicity studies have focused on freshwaters, where bioavailability is presumed to be higher. Recent studies have illustrated that some ENM formulations are bioavailable and bioactive in salt water and that their effects are more pronounced at the physiological than biochemical level. These findings raise concerns regarding the effects of ENMs on marine organisms. Therefore, our goal was to characterize the effects of polyvinylpyrolidone-functionalized silver ENMs (nAg) on aerobic performance in the killifish (Fundulus heteroclitus), a common euryhaline teleost. Fish were exposed to 80 µg L-1 of 5 nm nAg for 48 h in brackish water (12 ppt) and routine (MO2min) and maximum (MO2max) rates of oxygen consumption were quantified. Silver dissolution was minimal and nAg remained well dispersed in brackish water, with a hydrodynamic diameter of 21.0 nm, compared to 19.3 in freshwater. Both MO2min and MO2max were significantly lower (by 53 and 30%, respectively) in killifish exposed to nAg and a reduction in MO2 variability suggested spontaneous activity was suppressed. Neither gill Na+/K+-ATPase activity, nor various other biochemical markers were affected by nAg exposure. The results illustrate that a common ENM formulation is bioactive in salt water and, as in previous studies on functionalized copper ENMs, that effects are more pronounced at the whole animal than the biochemical level.