Bioaccumulation and Subchronic Physiological Effects of Waterborne Iron Overload on Whitefish Exposed in Humic and Nonhumic Water

One-year-old whitefish, Coregonus lavaretus, were exposed to three types of iron-rich water, two dilutions for each, in a subchronic (30-day) experiment. In natural iron-rich humic water, both the bioaccumulation and physiological effects of iron exposure were negligible. In humic-free water with high amount of additional inorganic iron (nominally 8 mg Fe/L), Fe accumulated in gills, liver, and gut. This accumulation was accompanied by decreased glycogen phosphorylase activities and microsomal EROD activity in the liver as well as decreased plasma sodium and potassium concentrations. The third group of whitefish were exposed by adding inorganic iron (nominally 2 and 8 mg Fe/L) to natural iron-rich humic water. Fish exposed to the higher concentration of waterborne iron exhibited a physiological stress response as indicated by increased blood lactate and plasma cortisol concentrations. Additionally, plasma 17β-estradiol concentration was increased in fish kept in both water conditions with high amounts of additional iron. The observed dissimilarities in bioaccumulation and in physiological responses were not connected with the measured amounts of total or disolved iron in water, but to the amount of additional iron in tanks and to the different water conditions with or without organic matter. The dissimilarity of physiological responses, which was also shown by statistical classification through multivariate discriminant analysis, points to the necessity of variable and complementary physiological endpoints in describing the effects of similar kind of exposures.