Fungal biomass associated with decaying leaf litter in a stream

Area of Science:

• Aquatic Ecology
• Mycology
• Biogeochemistry

Background:

• Leaf litter decomposition is a key process in aquatic ecosystems.
• Fungal communities play a crucial role in breaking down organic matter.
• Quantifying fungal biomass and production is essential for understanding stream ecosystem functioning.

Purpose of the Study:

• To measure fungal biomass on decomposing alder leaves in a Pyrenean stream.
• To estimate fungal production and growth efficiency during leaf decomposition.
• To assess the contribution of fungi to the decomposition process.

Main Methods:

• Ergosterol content was used as a measure of fungal biomass.
• Alder leaf litter was incubated in a softwater stream during autumn.
• Fungal production and growth efficiency were calculated based on ergosterol measurements and leaf mass loss.

Main Results:

• Ergosterol content in leaf litter increased rapidly, reaching a maximum of 462 μg/g detrital dry mass.
• Peak fungal mass represented 9.2% of total system mass and 10.2% of leaf dry mass.
• Net fungal production was estimated at 2.3 mg/day/g leaf mass, with a growth efficiency of 105 mg mycelial mass per gram leaf mass degraded.

Conclusions:

• Fungi achieve significant biomass and production during the decomposition of alder leaves in softwater streams.
• Ergosterol analysis provides a reliable method for estimating fungal biomass in stream ecosystems.
• Fungal activity is a major driver of leaf litter decomposition in this environment.