Effect Of Simulated Ocean Acidification Condition And Heavy Metals Of Cu And Cd On The Development, Reproduction And SOD Activity Of Tigriopus Japonicus

Heavy metals pollution in marine environment has caused great harm to themarine biological and ecological system. The excessed carbon dioxide in theatmosphere has caused the ocean acidification.The decreasing of pH value willseriously affect the growth,development and reproduction process of the marineorganism,and threaten the normal development of marine ecosystem.Copepods play an important role in the marine ecosystem. There is animportant scientific value to study the response of copepods to the ocean acidificationand heavy metal pollution. In the present study, we evaluated the effects of simulatedfuture ocean acidification and the toxicological interaction between ocean acidity andheavy metals of Cu and Cd on the development, breeding and SOD activity ofTigriopus japonicus. The harpacticoids were exposed in Cu and Cd concentrationgradient seawater which equilibrated with CO2and air to reach pH8.0,7.7,7.3and6.5. The main conclusions are as follow:1. Survival was not significantly suppressed under single sea water acidificationand the final survival rates were more than93%in both experimental groups andcontrols. The toxicity of Cu to T. japonicus was significantly affected by the sea wateracidification,96hLC₅₀decreased nearly threefold from1.98to0.64mg/L with pHdecreasing.96hLC₅₀of Cd showed a downtrend with pH decreasing but there was nosignificant difference of mortalities among pH treatments. The present resultsdemonstrated that the predicted future ocean acidification would potentiallynegatively affect survival of T. japonicus through exacerbating toxicity of Cu. Thecalculated safety concentration of Cu was11.9（pH7.7）and10.5（pH7.3）μg/L, whichless than the class I and very approximate the class II level of China National QualityStandard for Sea Water. It meant the Chinese coastal sea would face contamination threat from Cu with ocean acidification worsening in the future.2. The standard24days test indicates that: seawater acidification lengthened thedevelopment time of nauplius stage, but did not decrease its survival rate, the numberof egg clutch of T. japonicus, the number of nauplii and did not change thefemale/male ratio. The high concentrations of Cu delayed development of T.japonicus to adult stage under the natural water conditions, but there was nosignificant impact on the survival rate, the female/male ratio, the number of naupliiand the number of egg clutch of T. japonicus. The high concentrations of Cd alsolengthened development time of T. japonicus under the natural water conditions, butdid not decrease the survival rate, the female/male ratio and the number of eggs of T.japonicus. But with the increasing concentrations of Cd, the number of nauplius issignificantly reduced. In addition to affecting the development of T. japonicus, the Cuand Cd did not have a significant impact on the survival rate, the female/male ratio,the number of nauplii and the number of eggs of T. japonicus under the oceanacidification condition.3. The experiment showed that: Under the acidification conditions, the activityof SOD of T. japonicus increased at pH7.3, but the activity of SOD increased firstand then decreased at pH7.7and pH6.5. Under the natural seawater,there was not aobvious change tendency on the effect of Cu on the SOD activity.In the early stage ofthe experiment, the Cd made the activity of SOD being stimulated and increased. Butwith the extension of time, the activity of SOD was inhibited and decreased. Underthe acidification conditions, there were no significant differences on the activity ofSOD at different times under different concentrations of Cu. But the effects of Cd onthe activity of SOD of T. japonicus had a significant difference.