环境浓度下多菌灵、啶虫脒和草铵膦对微小亚历山大藻生长和产毒效率的影响OA

[Objective]Pesticides play a critical role in agriculture development and food security.China has been a major pesticide producer and consumer with an annual usage of over 1 million tons for the past two decades.Large amounts of pesticides continuously enter the aquatic environment through atmospheric deposition,surface runoff,etc.,threatening the health of aquatic ecosystems.Algae are the primary producers in aquatic environment.Frequently occurring algal blooms in the marine environment pose significant threats to ecosystem health.However,the interaction mechanisms between pesticides and algae are not thoroughly understood.[Methods]In this study,the individual and combined effects and mechanisms of pesticides on red tide algal growth and toxin production efficiency at environmental concentration levels were investigated using carbendazim,acetamiprid,and glufosinate,which are frequently detected in various aquatic environments,as target compounds,Alexandrium minutum as the testing alga,and with cell density,chlorophyll a content,maximum photochemical efficiency of photosystem Ⅱ(PS Ⅱ)(Fv/Fm),maximum relative electron transport rate(rETRmax),and algal toxins(GTX1-4)changes used as evaluation parameters.[Results]All three target pesticides individually inhibited algal growth by affecting photosynthesis,and the inhibition intensity significantly increased under different combinations(P＜0.05).In the study of individual effects on algal growth,the inhibitory effects of three target pesticides all increased with increasing concentration and cultivation time extension.The inhibition degree was ranked as glufosinate＞acetamiprid＞carbendazim.Among them,glufosinate exhibited significant inhibitory effects on cell density at all concentrations(P＜0.05).With the extension of the cultivation time,the degree of inhibition decreased first and then increased,reaching the highest value(37.07％-57.29％)on the 9th day.Acetamiprid and carbendazim at high mass concentration(100 ng/L)showed significant inhibitory effects on cell density(P＜0.05)with inhibition rates of 34.50％and 28.00％on the 9th day,respectively.At 1 and 10 ng/L,weaker inhibition with rates generally below 20％were observed.All three target pesticides inhibited chlorophyll a production and Fv/Fm,but did not significantly affect rETRmax,indicating that the impact of individual target pesticides on photosynthesis is mainly through the inhibition of maximum photochemical efficiency.In the study of combined effects on algae growth,all target pesticide combinations showed inhibitory effects.Carbendazim-acetamiprid and carbendazim-acetamiprid-glufosinate showed synergistic effects while carbendazim-glufosinate and acetamiprid-glufosinate showed antagonistic effects.The combined pesticides significantly inhibited chlorophyll a production,Fv/Fm,and rETRmax.Overall,low-concentration combinations inhibited algae growth,and the inhibitory effect increased with the extension of culture time.The influences during cell decline phase were significantly stronger than those during cell growth phase,indicating that the presence of pesticides accelerated algae death.In the study of the individual and combined effects of target pesticides on algal toxin production efficiency,all pesticides promoted toxin production during the cell decline phase,and the carbendazim-acetamiprid-glufosinate combination showed the greatest effect with a promotion rate of 75.61％-384.07％.[Conclusion]Overall,although pesticides exist in the aquatic environment at ng/L level,they can still affect the growth and photosynthesis of algae,and accelerate the release of cell toxins especially in the cell decline phase.These findings reveal that although pesticides can inhibit the growth of toxic red-tide algae to a certain extent,the rapid toxin release during cell decline phase may exacerbate environmental risks.The results of this study not only contribute to a more comprehensive understanding of the interaction between pesticides and toxic red-tide algae but also provide a scientific reference for developing effective environmental protection strategies.