Harmful algal blooms formed by the mixotrophic dinoflagellate Akashiwo sanguinea are toxic to multiple aquatic organisms, although the relationship between toxicity and grazing is unknown. In this study, the effects of irradiance and nutrient levels on the grazing rate of A. sanguinea on the cryptophyte Rhodomonas salina were investigated using an optimized stable isotope method. Under light-limited conditions (0–30 μmol photons m −2 s −1 ), A. sanguinea exhibited higher hemolytic activity and grazing rate. Under the same level of irradiance, the growth and respiration rates were higher in co-culture treatments, while the oxygen release rate was higher in monoculture treatments. The growth rate, hemolytic activity, and grazing rate of A. sanguinea increased significantly with higher nutrient levels or an unbalanced N:P ratio. The hemolytic activity and grazing rate were higher in urea treatment, while the growth rate was higher in ammonia treatment. This study suggests that toxicity is involved in the feeding process of the mixotrophic dinoflagellate A. sanguinea ; the unique feeding flexibility adapting to low irradiance, increased nutrients, unbalanced N:P ratio, and organic nitrogen urea gains an advantage in interspecific competition among phytoplankton.
The non-steroidal anti-inflammatory drug (NSAID) diclofenac is one of the most frequently studied as well as controversially discussed pharmaceutically active drug on the subject of its relevance to the environment. This study was conducted to assess the bioconcentration potential of diclofenac and its behavioral and biochemical effects in Daphnia magna . The bioconcentration factors of diclofenac determined after 48 h of aqueous exposure in Daphnia magna were 70.94 and 8.02 for the nominal exposure concentrations of 5 and 100 μg/L, respectively. Diclofenac exposure obviously decreased the filtration and ingestion rates of the daphnids. A significant increase of the acetylcholinesterase activity that was observed in this study indicates that diclofenac might not have neurobehavioral toxicity in Daphnia magna . Significant induction of malondialdehyde content is an indication of overproduction of reactive oxygen species leading to oxidative damage in daphnids after diclofenac exposure. Moreover, significant inhibition of the superoxide dismutase, catalase, and glutathione reductase activities implies that the antioxidant defense system of Daphnia magna was overwhelmed. Also, significant inhibition of glutathione s-transferase activity might point to the fact that the enzyme was not capable to detoxify diclofenac in Daphnia magna . These findings indicate that diclofenac can accumulate and consequently stimulate behavioral and biochemical disturbances in Daphnia magna .
危险品化学品经营许可证（带存储）