INFLUENCE OF WATER CHEMISTRY ON NICKEL ACCUMULATION AND SUB-LETHAL TOXICITY IN MARINE AND ESTUARINE ANIMALS

Abstract

Nickel (Ni) is a metal that is anthropogenically enriched in aquatic settings. It has been reported as having three main modes of toxicity in freshwater animals (ionoregulatory disturbance, respiratory impairment, and the generation of oxidative damage), but there is little understanding of Ni toxicity in marine and estuarine environments. The mechanism(s) of Ni uptake and toxicity were investigated using three model species (adult green shore crab, Carcinus maenas; adult Atlantic killifish, Fundulus heteroclitus; early life-stages of the New Zealand sea urchin Evechinus chloroticus). In crabs, sea water protected against Ni accumulation and toxicity. In more dilute salinities, however, all three modes of Ni toxicity were identified at a sub-lethal level, with effects noted at Ni exposure levels as low as 8.2 µg/L, the US EPA environmental regulatory limit. In killifish, similar protective effects of SW were observed, however this species was much more resilient to Ni toxicity, with only minor changes in ionoregulation and oxidative stress noted, and no evidence of respiratory toxicity. Sea urchin larvae were found to be the most sensitive marine organisms to Ni toxicity yet reported, with a 96 h median effect concentration of 14.1 µg/L measured. Toxicity in this species was related to Ni impairment of calcium influx, consistent with proposed mechanisms of uptake observed in the other two models. Overall, the elevated ion levels associated with salinity were shown to be protective, suggesting a role for water chemistry in modifying Ni accumulation. However, physiology, which varies between species, developmental stages, and as a function of environmental salinity, also influenced organism sensitivity to Ni. These data contribute novel information regarding the relationships between water chemistry, Ni accumulation, and Ni toxicity, and as such, will be integral in the future development of predictive modelling tools for protecting marine and estuarine animals against environmental Ni.