Studies focused on the relationship between biodiversity and ecosystem functioning have increased in recent decades due to concerns about the potential ecological consequences of biodiversity loss (Cardinale et al., 2012; Naeem et al., 1994; Tilman et al., 2014). Ecosystems are often valued for their capacity to maintain multiple processes, yet most studies assessing biodiversity–ecosystem functioning relationships have examined single processes in isolation (Hector & Bagchi, 2007). Among the different pathways of ecosystem functioning, biodiversity and ecosystem functioning studies have mostly focused on two opposite and fundamental processes controlling carbon and nutrient cycles globally (Field et al., 1998; Gessner et al., 2010): primary production, and how it is affected by the diversity of primary producers in the green compartment (Cardinale et al., 2011); and leaf litter decomposition, and how it is affected by the diversity of litter or consumers in the brown compartment (López-Rojo et al., 2019; Sanpera-Calbet et al., 2009). Biodiversity effects on these processes have mostly been considered separately, possibly because they are often dominant in different parts of the river network (Vannote et al., 1980). However, both processes generally co-occur, and studies should consider how biodiversity in both food web compartments and the processes occurring within them may interact to influence one another.