Biology and ecological functions of aquatic hyphomycetes in a warming climate

• Global warming effects on AH ecology are contradictory and conclusions context specific.
• Rising water temperature stimulates overall AH metabolism.
• Shifts in AH energetic allocations may affect litter quality and upper trophic levels.
• We expect warming to increase AH contribution to litter processing in streams.

The average global temperature is predicted to increase by 4 °C by the end of this century. Biotas of running waters, especially of low order streams, depend heavily on imports from the riparian vegetation. Autumn-shed leaves are decomposed and conditioned for invertebrate consumption by aquatic hyphomycetes. Overall metabolism, growth and reproduction of these fungi will be directly affected by rising temperatures and associated changes. Both resource (leaves) and consumers/competitors (leaf-eating invertebrates) will react to the same changes; their responses may indirectly influence fungal activities. Published studies on fungal reactions to climate change often reach contradictory and location-specific conclusions. Most commonly, at least in temperate streams, higher temperatures stimulate fungal metabolism, though there may be shifts in fungal allocations to enzyme activities, growth and reproduction. On a global scale, there is some evidence that rising temperatures will increase the contribution of aquatic hyphomycetes to litter processing in streams at the expense of invertebrates.