Environmental concentrations of metals (Cu and Zn) differently affect the life history traits of a model freshwater ostracod

Abstract

Zinc (Zn) and copper (Cu) are common contaminants of inland water bodies under severe anthropogenic pressure. The main aim of this study was to test the influence of environmental aqueous concentrations of Zn and Cu on the fitness-related life history traits of the cosmopolitan freshwater ostracod Heterocypris incongruens. Overall, eight subchronic laboratory experiments were conducted to test the effects of exposure to two Cu (260 and 460 µg Cu L−1) and Zn (230 and 410 µg Zn L−1) concentrations compared to the control conditions using asexual individuals originating from a wild population and from a commercial toxicity test (Ostracodtoxkit f). The response of ostracods to exposure to Zn and Cu differed considerably. The Cu treatments significantly reduced the total hatching success and hatching dynamics of resting eggs, increased the mortality of juveniles and reduced the survival of adults, dramatically decreasing the fitness of ostracods. On the other hand, the Zn treatments were less harmful and did not affect adult survival or the timing of juvenile hatching from subitaneous eggs but extended the timing of laying eggs at lower concentrations and stimulated hatching dynamics and success at higher concentrations. It seems that the increased Zn body burden did not strongly impact the fitness of the studied specimens. Moreover, the different responses of the laboratory and wild populations in the Zn experiments may suggest a genetic variation in the tolerance of ostracods to metals. Therefore, experiments involving laboratory H. incongruens as analogues of wild ostracods should be cautiously interpreted. We concluded that the major toxicant in our study was Cu, while Zn could be considered a micronutrient even supporting ostracod fitness, although its higher levels are likely to exert strong toxic effects.

Keywords

• Ostracodtoxkit f
• heavy metals
• aqueous exposure
• eggs viability
• bioconcentration