Response of antioxidant defense system in copepod Calanus sinicus Brodsky exposed to CO 2 -acidified seawater
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Response of antioxidant defense system in copepod Calanus sinicus Brodsky exposed to CO2-acidified seawater ZHANG Dajuan1, GUO Donghui2, WANG Guizhong2, LI Shaojing2* 1 Key Laboratory for Aquatic Ecology and Aquaculture of Tianjin, College of Fisheries, Tianjin Agricultural University,
Tianjin 300384, China 2 College of Ocean and Earth Science, Xiamen University, Xiamen 361005, China
Received 20 October 2014; accepted 11 September 2015 ©The Chinese Society of Oceanography and Springer-Verlag Berlin Heidelberg 2016
Abstract
Marine zooplankton responds sensitively to elevated seawater CO2 concentration. However, the underlying physiological mechanisms have not been studied well. We therefore investigated the effects of elevated CO2 concentration (0.08%, 0.20%, 0.50% and 1.00%) on antioxidant defense components, as well as two detoxification enzymes of Calanus sinicus (copepod). The results showed that glutathione peroxidase (GPx) activity exposed to CO2-acidified seawater was significantly stimulated while other antioxidant components, including glutathione-Stransferase (GST) activity, superoxide dismutase (SOD) activity decreased significantly with reduced glutathione (GSH) level and GSH/oxidized glutathione (GSSG) value. CO2-acidified seawater exhibited stimulatory effects on adenosine triphosphatase (ATPase) activity and acetylcholinesterase (AchE) activity was inhibited. Moreover, the results of principal component analysis indicated that 75.93% of the overall variance was explained by the first two principal components. The elevated CO2 concentration may affect the metabolism and survivals of copepods through impacts these enzymes activities. Further studies are needed to focus on the synergistic effects of elevated CO2 concentration and other environmental factors on copepods. Key words: acidified seawater, carbon dioxide, Calanus sinicus, antioxidant defense system Citation: Zhang Dajuan, Guo Donghui, Wang Guizhong, Li Shaojing. 2016. Response of antioxidant defense system in copepod Calanus sinicus Brodsky exposed to CO2-acidified seawater. Acta Oceanologica Sinica, doi: 10.1007/s13131-016-0870-5
1 Introduction Nearly 560 billion tons of fossil fuel-derived carbon dioxide (CO2) have been released into the atmosphere since the dawn of the industrial period (Doney et al., 2009). Although one-fourth to one-third of this has been taken up by the oceans, the atmospheric CO2 concentration raises to approximately 400 million volume (ppmv) (Sabine et al., 2004; Doney et al., 2009; http://www.esrl.noaa.gov/gmd/ccgg/trends/global.html). Ocean CO2 uptake causes decreased pH and increased partial CO2 pressure (pCO2). The pH is 0.1 units lower than that of the pre-industrial state, and it is expected to decrease by another 0.3–0.5 units if the atmospheric concentration of CO2 increases to 750 ppmv by the end of this century (Caldeira and Wickett, 2005; Orr et al., 2005). Sequestrating CO2 into the deep ocean has been proposed as an approach to mitigate the global warming. However, the pH around the sequestrated site
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