East China Sea Large-scale Red Tide Calanus Sinicus And The Neomysis Awatschensis The Eco-toxicological Studies

The effects of the large-scale blooms of Prorocentrum donghaiense and Kareniamikimotoi on the survival of Calanus sinicus were studied by in situ experiments andfield investigation in the East China Sea in the spring of 2005. The effects of theabove two algae and Alexandrium catenella(ACDH) on survival, ingestion, eggproduction and egg hatching of C. sinicus were examined under laboratory conditions.Moreover, we preliminarily studied the effects of P. donghaiense, K. mikimotoi andnine strains of Alexandrium spp. on survival, reproduction of Neomysis awatschensisin the laboratory. The results were shown as following:In situ experiments showed that both P. donghaiense and K. mikimotoi blooms atthe densities of 6×10~3 cells/ml reduced the survival rates of C. sinicus significantly.And the investigation showed that the survival percentage of C. sinicus in HABregion is lower than that in non-HAB region obviously. The laboratory studiesshowed that the survival rates of C. sinicus were obviously lower than that of controlwhen cell densities of P. donghaiense and A. catenella (ACDH) exceeded 2×10~4cells/ml and 2.5×10~3 cells/ml respectively. The survival rates decreased linearly withthe increasing of their densities, which 96hLC50 were 4.7×10~4 cells/ml and 3.5×10~3cells/ml respectively. However, K. mikimotoi had no significantly adverse effects onthe survival of C. sinicus in the experimental range. At the density of about 700cells/ml, C. sinicus can ingest P. donghaiense but few or no A. catenella (ACDH) norK. mikimotoi cells. The results also showed that the egg production of C. sinicusdecreased obviously when they were exposed to P. donghaiense (>500 cells/ml), K.mikimotoi (>5000 cells/ml) and A. catenella (ACDH) (>250 cells/ml), respectively,but the egg hatching was not affected by the three HAB species in the experimentalrange.P. donghaiense and K. mikimotoi had no significantly adverse effects on thesurvival of N. awatschensis in the experimental range. The survival rates decreasedlinearly with the increasing of the density of A. catenella(ACDH), which 96hLC50was 4.5×103 cells/ml. The survival rates of N. awatschensis obviously decreased whencell densities of A. catenella(ACDH) exceeded 2.5×103 cells/ml. At cell densities of500cells/ml and 1000cells/ml respectively, A. catenella(ACDH) could have influenceon fecundity of parents shrimp, which total number of juveniles were 82 % and 79 %of that of the control in 42 days. At the density of 4000 cells/ml, Alexandriumspp.(A-K, AL-1), Alexandrium tamarense (AT5-3) had no significantly adverse effectson the survival of N. awatschensis, but A. catenella (ACDH), Alexandrium minutum(AM-1) and Alexandrium tamarense (AT5-1, ATHK, ATCI02, ATCI03) reduced thesurvival rates of N. awatschensis significantly.The above research also indicated that C. sinicus was more sensitive to P.donghaiense and A. catenella(ACDH) than N. awatschensis. When the large-scaleblooms of P. donghaiense, K. mikimotoi and A. catenella(ACDH) occur in theChangjiang Estuary, the survival of zooplankton in this area would decrease, and thenumber of their offspring would be reduced. Moreover, HABs will last about onemonth and have thousands of square kilometers, so the zooplankton living in HABalgae of high density would be more seriously impacted. More species of zooplanktonand marine organisms would be influenced. Therefore, the large-scale algal blooms inthe East China Sea could have adverse effects on the population of zooplankton andfurther on the marine ecosystem.