Effects of increased temperature and aquatic fungal diversity on litter decomposition

Climate warming and biodiversity loss are two major factors threatening freshwaters. Aquatic hyphomycetes are fungi that play a key role in organic matter turnover in streams. To assess the impacts of temperature increase and aquatic hyphomycete diversity on plant-litter decomposition, we manipulated fungal assemblage composition at two levels of diversity (four and eight species) under ambient temperature of 16 °C and two regimes of temperature increase differing in 8 °C: abrupt versus gradual increase from 16 to 24 °C. The effects were evaluated on leaf-litter decomposition, fungal biomass and reproduction. Results showed faster leaf decomposition under increased temperature, but no differences were found between an abrupt and a gradual increase in temperature. Assemblage composition was the major factor controlling fungal biomass and reproduction, while fungal diversity was only critical to maintain reproduction.

► Aquatic fungi are recognized as playing a key role in plant-litter decomposition.
► We manipulated the identity and diversity of fungi under increased temperature.
► Temperature affected the structure of fungal assemblages and litter decomposition.
► Assemblage composition was mainly controlling fungal biomass and reproduction.