Biological Responses Of Three Marine Copepods To UV-B Radiation Enhancement

The copepod is one of the key loops of matter cycle and energy flow of the marine ecosystem. Its dynamics could significantly affect the primary productivity and the fluctuation of fish resource. Population dynamics and the productivity of the copepod would directly affect the structure and function of the whole marine ecosystem.Three marine copepods-Schmackeria inopinus, Eurytemora pacifica, Harpacticus were selected to serve as experimental materials. The present study of UV-B radiation enhancement on their growth, development, reproduction, ingestion and interspecific competition were estimated under controlled laboratory conditions. Moreover, the possible effective mechanism were studied from studying the effects of UV-B radiation enhancement on the physiological and biochemical aspects.Results showed:1. Comparison sensitivity of three marine copepods to UV-B radiation enhancement.E. pacifica was the most one and Harpacticus was the lest one to UV-B radiation enhancement among the three marine copepods. The order of sensitivity of the three marine copepods was E. pacifica > S. inopinus > Harpacticus. Among the three main development stage, the nauplii of S. inopinus and E. pacifica were more sensitive than these copepodites to UV-B radiation enhancement, and the copepodites was more sensitive than the adults. So the order of sensitivity of the main development stage is nauplii > copepodites > adults. Moreover, the female was more sensitive than male.2. The influence of UV-B radiation enhancement to reproduction of S. inopinus.UV-B radiation enhancement had stronger inhibitory effect reproduction of S. inopinus. The higher of UV-B radiation, the longer of the time of egg-bearing and gravid interval, and UV-B radiation enhancement could directly inhibit the gravid of S. inopinus.3. The influence of UV-B radiation enhancement on growth and development of S. inopinus and Harpacicus.UV-B radiation enhancement had no obvious influence on growth of S.inopinus and Harpacicus (p> 0.005), but remarkably inhibited the entire development progress of them. For S. inopinus, the time from Nâ…¡to adult significant prolonged (p< 0.001) when the UV-B agents were set at 0.0423 KJ/m2 and 0.0864 KJ/m2, and the time for the other stages increased as well as compared to the control. As to Harpacicus, an significance of the time from Nâ…¡to adult and for the whole development stage were observed as compared to the control when the UV-B agent was set 0.0423 KJ/m2 (p< 0.005), and an obvious significant difference was found when the agent was set at 0.0423 KJ/m (p< 0.001).4. The influence of UV-B radiation enhancement on metabolism of S. inopinus and Harpacicus.UV-B radiation presented similar effects on the oxygen consumption and ammonia excretion of female S. inopinus: higher UV-B radiation agents would result in more obvious damage on them. Conversely, different changing tendency was observed in the male S. inopinus. Its oxygen consumption rate decreased firstly and then increased and just the opposite change was found in the ammonia excretion rate. For Harpacicus, the male oxygen consumption rate was higher than the female, but no significant increase in oxygen consumption rate of female and male with UV-B radiation enhancement.5. The influence of UV-B radiation enhancement on ingestion of S.a inopinus and Harpacicus.The female S. inopinus had higher level of both filtration rate and ingestion rate than the male. High level of UV-B radiation decreased the ingestion rates than the male. While the low level of UV-B radiation (0.29 KJ/m2) not only couldn't decreased the filtration rate and ingestion rate of the female, but also stimulated the male to increase the filtration rate and ingestion rate. The filtration rate and ingestion rate of Harpacicus obviously decreased with UV-B radiation enhancement. The low levels of UV-B radiation (0.29, 0.58 and 0.87 KJ/m2) had no significantly influence on filtration rate and ingestion rate of the male Harpacicus (p> 0.005). While the high levels of UV-B radiation (1.16, 1.45 and 1.74 KJ/m2) obviously decreased the filtration rate and ingestion rate of the male.6. The influence of UV-B radiation enhancement on the interspecies competition between S.a inopinus and Harpacicus.In co-culture system of S. inopinus and Harpacicus, S.a inopinus play dominant role in the co-culture at the first 6 d, thereafter the amount of Harpacicu increased significantly and play the dominant role. UV-B radiation was more benefit for the Harpacicu, leading to the replacement of comparative advantage after 6 ds.7. The influence of UV-B radiation enhancement on the antioxidant system of S. inopinus.With the UV-B radiation enhancement, the concentration of O2- increased ,and there was no an obvious trend of the concentration of H2O2. The higer concentration of O2-, the more serious lipid peroxidation of S. inopinus happened, and the concentration of MDA continuously increased. Low agent of UV-B radiation could stimulate the antioxidant system, and high agent of UV-B radiation had an obvious inhibitory effect on it.UV-B radiation enhancement obviously influenced the S. inopinus, the possible effective mechanism was: UV-B radiation inhibited the antioxidant system of S. inopinus, leading to the high concentration of O2-. And the lipid peroxidation which coursed by O2- resulted in the membrane damage. So the growth, development, reproduction, ingestion and interspecific competition of S. inopinus were influenced by UV-B radiation enhancement.