Zooplankton are important biocontrol agents for algal blooms in temperate lakes, while their potential in tropical and subtropical environments is not well understood. The aim of the present study was to evaluate the influence of increased zooplankton biomass on phytoplankton community and cyanotoxins (microcystins and saxitoxin) content of a tropical reservoir (Ipojuca reservoir, Brazil) using in situ mesocosms. Mesocosms consisted of 50 L transparent polyethylene bags suspended in the reservoir for twelve days. Phytoplankton populations were exposed to treatments having 1 (control), 2, 3 and 4 times the biomass of zooplankton found in the reservoir at the beginning of the experiment. Filamentous cyanobacteria such as Planktothrix agardhii and Cylindrospermopsis raciborskii were not negatively influenced by increasing zooplankton biomass. In contrast, the treatments with 3 and 4 times zooplankton biomass negatively affected the cyanobacteria Aphanocapsa sp., Chroococcus sp., Dolichospermum sp., Merismopedia tenuissima, Microcystis aeruginosa and Pseudanabaena sp.; the diatom Cyclotella meneghiniana; and the cryptophyte Cryptomonas sp. Total microcystin concentration both increased and decreased at different times depending on zooplankton treatment, while saxitoxin level was not significantly different between the treatments and control. The results of the present study suggest that zooplankton biomass can be manipulated to control the excessive proliferation of non-filamentous bloom forming cyanobacteria (e.g. M. aeruginosa) and their associated cyanotoxins.

浮游动物是温带湖泊中藻华的重要生物防治剂，但它们在热带和亚热带环境中的潜力尚未得到很好的了解。本研究的目的是使用原位中观介导评估增加的浮游生物量对热带水库（巴西伊波茹卡水库）浮游植物群落和藻毒素（微囊藻毒素和沙毒素）含量的影响。中观膜由50 L透明聚乙烯袋组成，该聚乙烯袋在水库中悬浮十二天。在实验开始时，对浮游植物种群进行的处理具有在储层中发现的浮游动物生物量的1（对照），2、3和4倍。丝状蓝细菌，如浮游植物琼脂（Planktothrix agardhii）和浮游动物生物量的增加不会对圆环柏有负面影响。相反，用浮游生物量的3倍和4倍处理对蓝细菌Aphanocapsa sp。，Chroococcus sp。，Dolichospermum sp。，Merismopedia tenuissima，Microcystis aeruginosa和Pseudanabaena sp。产生负面影响。硅藻Cyclotella meneghiniana ; 和隐藻类隐孢子虫sp。根据浮游动物的治疗方法，总微囊藻毒素浓度在不同时间都有所增加和减少，而各处理和对照组之间的毒素含量没有显着差异。本研究的结果表明，可以控制浮游生物的生物量，以控制非丝状形成蓝藻的蓝藻（例如铜绿假单胞菌）及其相关的蓝藻毒素的过度繁殖。