Higher temperature reduces the effects of litter quality on decomposition by aquatic fungi

Abstract

Summary 1. We investigated the effects of riparian plant diversity (species number and identity) and temperature on microbially mediated leaf decomposition by assessing fungal biodiversity, fungal reproduction and leaf mass loss. 2. Leaves of five riparian plant species were first immersed in a stream to allow microbial colonisation and were then exposed, alone or in all possible combinations, at 16 or 24 °C in laboratory microcosms. 3. Fungal biodiversity was reduced by temperature but was not affected by litter diversity. Temperature altered fungal community composition with species of warmer climate, such as Lunulospora curvula, becoming dominant. 4. Fungal reproduction was affected by litter diversity, but not by temperature. Fungal reproduction in leaf mixtures did not differ or was lower than that expected from the weighted sum of fungal sporulation on individual leaf species. At the higher temperature, the negative effect of litter diversity on fungal reproduction decreased with the number of leaf species. 5. Leaf mass loss was affected by the identity of leaf mixtures (i.e. litter quality), but not by leaf species number. This was mainly explained by the negative correlation between leaf decomposition and initial lignin concentration of leaves. 6. At 24 °C, the negative effects of lignin on microbially mediated leaf decomposition diminished, suggesting that higher temperatures may weaken the effects of litter quality on plant litter decomposition in streams. 7. The reduction in the negative effects of lignin at the higher temperature resulted in an increased microbially mediated litter decomposition, which may favour invertebrate‐mediated litter decomposition leading to a depletion of litter stocks in streams.

Diversity and community composition of aquatic ascomycetes varies between freshwater, estuarine and marine habitats in western Scotland

“…Highest diversity in the present study was in the river habitat, with lowest salinity and temperature as observed previously for temperature (Fernandes et al 2012, Hyde et al 2016) and salinity (Shearer 1972, Tsui et al 2001, 2004, Fryar et al 2004, Pearman et al 2010, Richards et al 2012. However, a multitude of factors affect aquatic fungal diversity and a combination of these result in the diversity seen across habitats.…”

“…Aquatic hyphomycetes are adapted to lotic freshwater environments growing on dead plant material such as leaf litter (Ingold 1942, Medeiros et al 2009, Fernandes et al 2012) and submerged lignicolous material (Yuen et al 1998, Vijaykrishna et al 2006, Shearer et al 2007, Kuehn 2016. Sexual ascomycetes also display adaptations to aquatic environments (Willoughby & Archer 1973, Pearman et al 2010, and facilitate decomposition and softening of lignicolous wood substrates (Hyde et al 2016).…”

In-stream litter decomposition along an altitudinal gradient: does substrate quality matter?

“…In these environments, some authors (Fierer et al, 2005;Conant et al, 2008;Wetterstedt et al, 2010) have reported that low-quality material decomposition (structurally complex C substrates) appears to be more sensitive to temperature increase than high-quality ones, possibly because the microbial enzymatic reactions require a higher net activation energy to metabolise structurally complex C substrates (Bosatta & Å gren, 1999). This suggests that organic substrate quality would have a significant and predictable influence on the sensitivity of microbially mediated decomposition to temperature, which might also occur in freshwater ecosystems (Fernandes et al, 2012). However, whereas studies on individual effects of these two factors on litter processing are common in the literature, few studies have so far addressed the interaction between temperature and detritus quality and their implications on litter processing in freshwater ecosystems (see Ferreira & Chauvet, 2011a;Fernandes et al, 2012;Gonçalves et al, 2013).…”

The leaf breakdown of Picramnia sellowii (Picramniales: Picramniaceae) as index of anthropic disturbances in tropical streams

“…The increase in water temperature can accelerate the leaching of soluble compounds and favor microbial activity, positively influencing the leaf breakdown (Fernandes et al, 2012). However, we observed that urbanization (increase in electrical conductivity, water temperature, turbidity and NO 2 ; and decrease in dissolved oxygen) had a negative effect on the leaf breakdown of P. sellowii, probably due to the fact that these streams contain lower fungal biomass and no invertebrate shredders.…”