Effects of waterborne mercury at different temperatures on hematology and energy metabolism in grass carp ( Ctenopharyng
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ORIGINAL PAPER
Effects of waterborne mercury at different temperatures on hematology and energy metabolism in grass carp (Ctenopharyngodon idella) Z.‑H. Li1,2 · P. Li1 · Y. Wu2 Received: 19 May 2020 / Revised: 30 July 2020 / Accepted: 24 August 2020 © Islamic Azad University (IAU) 2020
Abstract 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 H g2+ for 2+ 4 weeks. Three-way ANOVA revealed that all variables were significantly affected by water temperature, Hg concentration, exposure time and their interactions, except the RBCs value corresponding Hg*Time condition. Based on the significant changes of hematological parameters in H g2+-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 H g2+ 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. Keywords Thermal stress · Mercury · Fish · Physiological adaption
Introduction In the last decades, temperature rise related to climate change caused the structural and functional changes of aquatic ecosystem (Val et al. 2016), that led to the decrease in dissolved oxygen, the acceleration of eutrophication and the decrease in aquatic biodiversity. Besides, the threat of environmental pollutants to aquatic organisms was increasingly serious, so the coupling stress of temperature fluctuation and water pollution on aquatic organisms has attracted more and more attention (Balbus et al. 2013; Lee et al. 2014; Abdel-Tawwab Editorial responsibility: Jing Chen. * Z.‑H. Li [email protected] 1
Marine College, Shandong University, Weihai 264209, Shandong, China
Yangtze River Fisheries Research Institute, Chinese Academy of Fishery Sciences, Wuhan 430223, China
2
and Wafeek 2017). As far as the harmful effects on water ecosystem, metal mercury (Hg) is one of the most studied and most concerned pollutants and has been considered an environmental stressor (Li et al. 2014). In China, environmental concentrations of mercury were ranging from 0.031 to 5.7 μg/L in the natural rivers (Biscere et al. 2015). Once the
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