The role of cladocerans in green and brown food web coupling

ABSTRACT Cladocerans, an important zooplankton community, are consumers from the base of the food web of aquatic environments. We investigated the contribution of producers (phytoplankton and periphytic biofilm) and particulate organic carbon (POC). Collections were carried out in lakes of the Upper Paraná River Floodplain, the last stretch free of dams in the second-largest South American basin. Isotope ratios (δ13C and δ15N) were measured, besides the contributions of probable food sources to the cladocerans biomass. The phytoplankton constituted the source of carbon for cladocerans, followed by POC. Thus this work, in addition to emphasizing the importance of cladocerans in nutrient cycling, highlighted the need for the conservation of environments surrounding the lakes as they are the sources of organic matter for aquatic communities. Besides, the analyzed zooplanktonic organisms demonstrated their role in the interconnection between the green and brown food webs, which have been studied separately for a long time.

摘要：枝角类(Cladocerans)是一类重要的浮游动物类群，为水生环境食物网基底层级的消费者。本研究探讨了初级生产者（浮游植物(phytoplankton)、周生生物膜(periphytic biofilm)）与颗粒有机碳(POC)对枝角类的食物贡献。样品采集工作在南美洲第二大流域内最后一处未受大坝阻隔的河段——巴拉那河上游泛滥平原的湖泊中开展。研究测定了碳稳定同位素比值(δ¹³C)与氮稳定同位素比值(δ¹⁵N)，并估算了各类潜在食物源对枝角类生物量的贡献份额。结果显示，浮游植物是枝角类的主要碳源，其次为颗粒有机碳。本研究不仅强调了枝角类在营养盐循环中的重要作用，同时也指出需加强湖泊周边环境的保护——因为这些环境是水生生物群落的有机质来源。此外，本次分析的浮游动物类群证实了其在绿色食物网与棕色食物网之间的连接作用，而这两类食物网长期以来均为独立研究的对象。