有毒亚历山大藻对卤虫存活率和摄食率的影响

研究了有毒亚历山大藻对卤虫存活率和摄食率两方面的影响，得出以下结论：在卤虫存活率实验中，有毒亚历山大藻在2000cells／ml的密度下，对卤虫具有致死效应，卤虫在24-168h内全部死亡；在摄食实验中，有毒亚历山大藻对卤虫的摄食产生明显的抑制作用，卤虫对有毒藻的平均摄食率明显低于无毒藻组和混合实验组。在加入无毒藻东海原甲藻的混合培养状态下。卤虫存活率上升，30-60min摄食率增加，东海原甲藻在一定程度上可以减轻塔玛亚历山大藻对卤虫的毒害作用。有毒藻产生的PSP毒素并非导致卤虫死亡的主要原因，毒害作用可能与出现在卤虫体外的黏附物质有关。通过对3个不同生长期卤虫的研究发现，后无节幼体卤虫对有毒亚历山大藻的毒害作用最为敏感。

The effects of toxic Alexandrium species on thesurvival and feeding rateof brine shrimp Artemia salina

Zooplankton is an important link between phytoplankton and higher consumers in the marine food chain. To investigate the harmful effects of the toxic dinoflagellate Alexandrium species on zooplankton, 4 strains of Alexandrium spp., isolated from the Chinese coast, were used to test the species' effects on the survival and feeding rates of the brine shrimp, Artemia salina. The experiment was designed to assess the response of A. salina in each stage of its life cycle: nauplii, metanauplii, and adult. Each experiment was conducted in a 500 ml treatment that was added. The toxic treatments consisted of single strains of A. minutum, A. catanella, and A. tamarense (Nanhai and Donghai strain), while non-toxic species (dinoflagellate Prorocentrum donghaiense and diatom Chaetoceros minutissimus) were used as control treatments. An additional phytoplankton treatment consisted of, a mixture of A. tamarense (Nanhai strain) and P. donghaiense. Alexandrium spp. species were found to have lethal effects on the brine shrimp at a density of 2000 cells/ml. All the brine shrimps died within 24-168 hours of inoculation with the 4 treatments each containing single toxic Alexandrium species. During the feeding experiment, toxic Alexandrium spp. caused a reduction in the feeding rates in all the three stages of the life cycle of A. salina, whereas this response was not obvious in the treatment involving the nontoxic species P. donghaiense. The body surface of the brine shrimp that were fed on Alexandrium species was consistently covered by a sticky floc. Mortality of A. salina was observed to increase with the occurrence of the floc. The toxicity of the paralytic shellfish poisons (PSP) produced by the Alexandrium species was not significantly correlated with the survival or the feeding rate of the brine shrimp. When A. tamarense was mixed with P. donghaiense, the lethal effect of A. tamarense decreased, as shown by an increase in the survival and the feeding rates of the brine shrimp. A. salina metanauplii were found at the life stage most sensitive to the toxic algae and hunger. In summary, toxic Alexandrium spp. were found to have lethal effects on A. salina and to restrain the brine shrimp's feeding rate. Nontoxic Prorocentrum mitigated the toxicity of Alexandrium to a certain extent. The results also imply that the sticky material on the surface of the body of the brine shrimp may have been an important lethal factor rather than the PSP toxins.