Changes on plasmatic electrolytes and behavior of freshwater fish, Luciobarbus bocagei, as a function of acute copper exposure

Abstract

Copper is continuously increasing in water and its toxic effects on aquatic organisms arise, among others, from biochemical interactions. In Northeastern Portugal, different watercourses are suffering negative impacts, namely in the Portelo stream, affected by collapse and continuous input of mining deposits, including Cu content. Therefore, the impact of sub-lethal Cu concentrations on fish Na+, K+ and Ca2+ plasma concentrations was evaluated to assess osmoregulatory adverse effects. Also, the same evaluations were conducted after fish were changed to clean water, to assess fish ability to revert electrolytes levels. Acute toxicity tests were conducted, using barbels (Luciobarbus bocagei) under two different copper concentrations. Fish behavior and Condition Factor (K) were also evaluated. Barbels under Cu exposition showed several changes at physiological and behavioral levels, such as ion imbalance, lowere aerobic scope and mortality and reduced K. According to our results, plasma K+ and Ca2+ levels may increase, while Na+ levels may decrease in fish exposed to Cu, allowing fish to an osmotic adjustment and reduced susceptibility to Cu, in an attempt to survive under environmental stress. Under the conditions of these experiments, fish also showed a capacity to reverse levels of electrolytes, when they cease to be exposed to Cu; however, that depends upon exposure concentration.