LAUSR

Aquatic ecosystem is greatly affected by metal pollution and global climate change. Mercury (Hg) is one of the most common metal pollutants that pose harmful effects to organisms. In this study, we evaluated the effects of water temperature and Hg2+ on hematological parameters, such as red blood cells (RBCs), hematocrit (Ht) and hemoglobin (Hb) and some indexes involved in energy metabolism, including hexokinase (HK), pyruvate kinase (PK), malate dehydrogenase (MDH), lactate dehydrogenase (LDH), glucose (GLU), electron transport system (ETS) and Na–K-ATPase in grass carp, Ctenopharyngodon idella. Fish (45.37 ± 3.58 g) were acclimated to 15, 20, 25, 30 or 35 °C and co-exposed to 0.000 or 0.039 mg/L Hg2+ for 4 weeks. Three-way ANOVA revealed that all variables were significantly affected by water temperature, Hg2+ concentration, exposure time and their interactions, except the RBCs value corresponding Hg*Time condition. Based on the significant changes of hematological parameters in Hg2+-free groups, the best health status in fish was approximately at 25 °C, appreciating physiological dysregulation in fish under too low (15 °C)/high (35 °C) temperature, especially at 35 °C. Although our data provide evidences that increased temperatures can potentiate Hg2+ toxicity, the combined effects of temperature and metals on aquatic organisms are complex and unpredictable, so we should not ignore the role of environmental factors (such as temperature) while evaluating the harmful effects of metals on aquatic ecosystem.