| 其他摘要 | Concentration of carbon dioxide (CO2) has went up sharply, as a result of fossil fuel use and human activities including deforestation and overgrazing since the Industrial Revolution. Being the largest carbon sink, the ocean has absorbed more than 30% of CO2 caused by activities of humankind, leading to a decrease of seawater pH to 0.1, as this process was defined as ocean acidification. Papers have showed ocean acidification could have influence on the carbonate buffer system, chemical environment of seawater and biological activities, such as gene expression, energy metabolism and cellular stress. Besides, the seawater acidification would also affect the development, reproduction, and biological calcification of marine organisms.
Simultaneously, a large amount of Cu2+-containing industrial wastewater, domestic sewage, and agricultural water along with human activities are brought into the offshore waters through river runoffs, causing a high enrichment of the copper content in some offshore areas. As one of the most widely distributed environmental pollutants, High concentration of copper can cause the occurrence of abnormal antioxidant system abnormalities, energy metabolism disorders, and genotoxic effects on marine organisms, do damages to tissues, even result in death of marine organisms at high concentrations. Ocean acidification may change the form of heavy metals in the water environment, and promote the migration of metal ions such as Cu2+ from sediments to seawater, hence increasing the concentration of Cu2+ in the seawater environment and the bioavailability of aquatic organisms. Furthermore, literatures also pointed out ocean acidification would affect the physiological metabolic processes of marine biological populations indirectly by changing the biological effects and potential toxicity of pH-sensitive metals.
Aurelia coerulea is a widely distributed glial zooplankton in the ocean, plays an important role in the biogeochemical cycle of important elements consist of carbon, nitrogen, phosphorus the energy flow and material cycle of the marine ecosystem. In the present study, we focused on the polyps and ephyrae in the early stages of A. coerulea, and addressed the current acidification and heavy metal pollution in the ocean. Moreover, this study explored the physiological responses of the polyps and ephyrae to ocean acidification and Cu2+ stress, we expected to provide a scientific basis for ecological risk assessment of ocean acidification and heavy metal pollution in the context of global climate change.
The main research process and results are as follows:
（1）The effects of ocean acidification and Cu2+ stress on polyps could be reflected on activities of catalase (CAT), superoxide dismutase (SOD), Ca2+-ATPase, Na+K+-ATPase, acid phosphatase (ACP) and alkaline phosphatase (AKP). Physiological indicators including budding asexual reproduction rate, respiration rate, feeding rate and histopathological changes were also determined to evaluate the toxic effects of ocean acidification and Cu2+ exposure on polyps of A. coerulea. The results exhibited that ocean acidification and Cu2+ exposure inhibited the activities of CAT, Ca2+-ATPase, ACP, AKP of polyps notably, resulting in antioxidative stress effects and significantly increasement on respiratory metabolism. In addition, the combination of ocean acidification and Cu2+ exposure would also do severe tissue toxicological damages to polyps, which in turn affected the predation behavior of polyps and reduced feeding rate and asexual reproduction rate. The two environmental stress factors showed synergistic effects in terms of Ca2+-ATPase activity, feeding rate, reproduction rate, and injury index.
（2）In the study of A. coerulea ephyrae, the activities of physiological metabolic enzymes including CAT, SOD, Ca2+-ATPase, Na+K+-ATP, ACP and AKP, as well as respiration rate, contraction frequency and umbrella diameter were measured. The physiological response of A. coerulea ephyrae under ocean acidification and Cu2+ stress was analyzed as well. The results suggested that ocean acidification and Cu2+ stress had different effects on the activities of six enzymes. Cu2+ exposure significantly inhibited the activities of CAT, Ca2+-ATPase and AKP, as well as the contraction frequency and growth rate of A. coerulea ephyrae, resulting in an abnormal increase in SOD activity and respiratory rate. Moreover, copper pollution might affect the movement ability of A. coerulea, leading to the decline in the predation ability of A. coerulea, and significantly inhibits growth. There’s a positive correlation between the umbrella diameter of A. coerulea ephyrae and pH, whereas a negative correlation was observed between the umbrella diameter and Cu2+ concentration. Single-factor exposure to ocean acidification also restrained the growth of ephyrae, but had an antagonistic effect on Cu2+ toxicity. Ocean acidification alleviated the stimulating effect of Cu2+ on the respiration rate of A. coerulea ephyrae, the inhibitory effect of contraction frequency and growth rate. This may indicate that with ocean acidification being the background, it seems probably that the adaptability of A. coerulea ephyrae to copper pollution is enhanced.
（3）The sensitivity of A. coerulea to the two environmental stress factors consist of ocean acidification and Cu2+ was different in polyps and ephyraes. Under the same exposure conditions, Na+K+-ATPase, ACP, AKP and other physiological indicators such as oxygen consumption rate showed different patterns. The interactions between ocean acidification and Cu2+ exposure was different in two life history stages. Ocean acidification and Cu2+ exposure had a synergistic effect on the toxic effects of A. coerulea polyps, while ocean acidification could alleviate the toxic effect of Cu2+ on the ephyrae, reduce the oxidative stress effect caused by Cu2+ exposure, and increase the contraction frequency and growth rate of ephyrae.
This study identified the different physiological effects of ocean acidification and Cu2+ exposure on the two stages of the polyps and ephyrae of A. coerulea. This differential response might change the survival strategy of A. coerulea in the future, affecting marine biological diversity sexuality and ecosystem stability. The results of this study will provide a theoretical basis and technical support for assessing the impact of global and regional marine environmental problems on marine life and marine ecosystems, as well as marine environmental monitoring. |
修改评论