Fine sediment on leaves: shredder removal of sediment does not enhance fungal colonisation

Abstract

Inorganic fine sediments are easily carried into streams and rivers from disturbed land. These sediments can affect the stream biota, including detritivorous invertebrates (shredders) and impair ecosystem functions, such as leaf litter decomposition. We hypothesized that fine sediment (kaolin) deposited on leaves would reduce or suppress fungal development, reducing decomposition rates of leaves. Moreover, we predicted that shredders would act as ecosystem engineers by perturbing sediment deposition, reducing its impact on decomposition and fungi. We used a fully crossed experimental design of sediment addition (control, 400 mg L -1 ) and shredders (none, Gammarus, Potamophylax) in laboratory aquaria. Leaf mass loss, suspended solids, microbial respiration, fungal biomass and spore production were measured. Sediment addition had no significant effects on the leaf mass remaining nor on shredders' consumption rates. However, sediment slightly reduced fungal assemblage richness and the sporulation rate of three fungal species. The presence of shredders substantially increased the resuspension of fine sediments ([300%), resulting in higher suspended loads. However, the action of shredders did not have a significant effect on fungal biomass nor on leaf mass loss. Even if shredders did not enhance fungal colonisation, they affected the settlement of fine sediment, serving as allogenic engineers. Our study suggests that concentrations of fine sediment of 400 mg L -1 with short exposure times (192 h) can have some effect on leaf decomposition.

Small stonefly predators affect microbenthic and meiobenthic communities in stream leaf packs

“…At the end of the experiment, the amount of sediment trapped in leaf packs in the high predator density treatments (6 and 9 Chloroperlidae) was nearly twofold lower than in controls. This finding is fully in line with empirical evidence of the strong control by macrobenthos of fine sediment deposition and retention on stones (Zanetell & Peckarsky, ; Lecerf & Richardson, ) and decaying plant litter (Zhang, Richardson & Negishi, ; Sanpera‐Calbet, Chauvet & Richardson, ; Majdi et al ., ). Specifically, bioturbation caused by actively hunting predators, such as Chloroperlidae, may reduce the amount of deposited sediment (Zanetell & Peckarsky, ; Zhang et al ., ).…”

“…Biotic disturbance and the consolidation of fine sediments, whether mediated by predacious or non-predacious species (e.g. Zhang et al, 2004;Sanpera-Calbet et al, 2012;Majdi et al, 2014), may be critically important in determining the colonisation of leaf litter by the micro-and meiobenthos. The negative effects of predators on the density and biomass of putative prey (i.e.…”

Forest canopy cover determines invertebrate diversity and ecosystem process rates in depositional zones of headwater streams

“…There are at least of two mechanisms accounting for this correlation between the two processes. First, fine particle reworking and excavation behaviour can reduce the adverse effect of sedimentation on litter breakdown by making leaf litter more accessible to consumers (Creed et al, 2010;Sanpera-Calbet, Chauvet & Richardson, 2012). Second, bioturbation in lentic habitats could promote the conditioning and mineralisation of leaf litter by microbial decomposers through enhanced nutrient transfer from sediment to leaf litter (Mermillod-Blondin, 2011;Hunting et al, 2012).…”

Effects of two sorbents applied to mercury-contaminated river sediments on bioaccumulation in and detrital processing by Hyalella azteca

“…2 and 3), a process that is central in many aquatic ecosystems, especially in those with a dense canopy and relatively low autotrophic production (Fisher and Likens 1973). However, detrital processing can also be reduced by natural fine particles settling onto leaf litter in streams (Sanpera-Calbet et al 2012). Therefore, the reduction in detrital processing induced by Sedimite ® should be related to the potential implications of such natural particles.…”