Fungal alteration of the elemental composition of leaf litter affects shredder feeding activity

Abstract

1. Leaf litter from riparian vegetation provides the main source of matter and energy for food webs of small forest streams. Shredding macroinvertebrates mostly feed on this litter when it has been colonised and conditioned by microorganisms, especially by aquatic hyphomycetes. Since shredders feed selectively, they must make foraging decisions based on the physical and chemical characteristics of the food resource, which can change depending on the identity of fungal species. 2. Here, we addressed the effect of changes in fungal assemblage structure on the elemental composition of oak (Quercus robur) leaf litter and how variation in litter quality affects the feeding of a stream shredder. Leaf discs were incubated in microcosms for 2 weeks, inoculated with various fungal assemblages comprised of three species each, and offered to a shredder (Schizopelex festiva, Trichoptera: Sericostomatidae) as food. 3. This shredder ate more leaves with a high mycelial biomass, which depended on fungal assemblage composition. Leaf litter conditioned by different fungal assemblages resulted in different litter N and P concentrations. Mycelial biomass was positively related to litter P concentration, with the lowest and highest P concentrations differing by 40% at most, but not to litter N concentration, even though the lowest and highest N concentrations differed by as much as 35%. The caddisfly larvae ate more leaves with a low C/P ratio. 4. These findings suggest a key role of litter P concentration in eliciting fungal conditioning effects on shredder-mediated litter decomposition.

Detritivore stoichiometric diversity alters litter processing efficiency in a freshwater ecosystem

“…As detritivores in fresh water ecosystems maintain low N: P ratios in their bodies relative to detritus (Evans‐White et al ), they might respond to P availability rather than N availability. Furthermore, fungal biomass on leaf litter alters feeding activity of shredders through effects on nutrient composition of litter (Cornut et al ). RB species in our experiment also ate more Alnus japonica and Styrax obassia with high microbial biomass (Table , , Fig.…”

Fungal contributions to carbon flow and nutrient cycling during decomposition of standing Typha domingensis leaves in a subtropical freshwater marsh

“…This paradigm contrasts sharply with our knowledge of other freshwater ecosystems, such a streams, where aquatic hyphomycete fungi have been widely recognised as an important microbial group that is central to litter decomposition and detrital food resources for inhabitant consumers (e.g. B€ arlocher, 1992;Gessner & Chauvet, 1994;Suberkropp, 2001;Gulis & Suberkropp, 2003a,b;Gulis et al, 2006;Gessner et al, 2007;Chung & Suberkropp, 2009;Cornut et al, 2015).…”

High-quality algae attached to leaf litter boost invertebrate shredder growth

“…The effect of fungi on invertebrate growth depends on different fungal assemblages (Cornut et al 2015), and fungal growth and production may be stimulated by algae under open-canopy conditions (Kuehn et al 2014). The high abundance of low-quality algae contributed to smaller shredder size in the O treatment.…”