Mansano A S, Hisatugo K F, Hayashi L H, Regali-Seleghim M H
Departamento de Ecologia e Biologia Evolutiva, Universidade Federal de São Carlos - UFSCar, São Carlos, SP, Brazil.
Braz J Biol. 2014 Aug;74(3):569-78. doi: 10.1590/bjb.2014.0081.
This study evaluated the importance of heterotrophic nanoflagellates (HNF) and ciliates bacterivory in a mesotrophic subtropical environment (Lobo-Broa Reservoir, Brazil) by the quantification of their ingestion rates. The in situ experiments using fluorescently labelled bacteria (FLB) were carried out bimonthly over one year (three surveys in the dry season and three in the rainy one) at the sub-surface of two sampling points that have different trophic degrees. The ingestion rates for both ciliates and HNF were higher in the meso-eutrophic region (point 2) due to the higher water temperatures, which accelerate the metabolism of protozoans and the higher bacteria densities. Concerning total protozoan bacterivory, the HNF had the greatest grazing impact on bacterial community, especially the HNF <5 µm. The data showed that HNF grazing, in addition to regulating the bacteria abundance, also induced changes to the bacterial community structure, such as increasing size and numbers of bacterial filaments. The ciliates were also important to the system bacterivory, especially in point 2, where there were high densities and ingestion rates. The protozoan bottom-up control was more important in the dry season and the top-down control was more important in the rainy season, so, these two forces are equally important to the bacterial abundance regulation in this reservoir in an annual basis.
本研究通过量化异养型纳米鞭毛虫（HNF）和纤毛虫的食细菌率，评估了它们在亚热带中营养环境（巴西洛博-布罗阿水库）中的重要性。使用荧光标记细菌（FLB）的原位实验在一年中每两个月进行一次（旱季三次调查，雨季三次），在两个营养程度不同的采样点的次表层进行。由于水温较高，中富营养区域（点2）的纤毛虫和HNF的摄食率均较高，水温升高会加速原生动物的新陈代谢，且细菌密度也更高。关于原生动物的总食细菌量，HNF对细菌群落的放牧影响最大，尤其是<5 µm的HNF。数据表明，HNF放牧除了调节细菌丰度外，还会引起细菌群落结构的变化，例如增加细菌丝状体的大小和数量。纤毛虫对系统的食细菌作用也很重要，特别是在点2，那里有高密度和高摄食率。原生动物的自下而上控制在旱季更为重要，自上而下控制在雨季更为重要，因此，这两种力量在一年中对该水库细菌丰度的调节同样重要。
