Work

Past flow intermittence duration influences microbial and invertebrate community structure and ecological processes after flow resumption

Year: 2026

Type: article

Abstract: Intermittent streams represent over half of the global river network and are becoming increasingly prevalent due to climate change and water abstraction. Despite their importance, knowledge of their functioning remains limited, especially in temperate regions. Here, we assessed the effects of past flow intermittence duration on functional processes during the flowing period in two temperate streams of northeastern France, using functional indicators (i.e., organic matter decomposition and primary production) and monitoring aquatic fungal and invertebrate communities. Indicators were deployed at 12 stations distributed along an intermittence gradient in two contrasting watersheds. We tested whether (1) past drying duration influences functional processes during the flowing phase, (2) drying effects differ between the two streams, and (3) functional indicators are relevant to intermittent stream systems and discriminant enough for assessing drying duration stress. Our results revealed contrasting functional responses between the two systems despite comparable flow intermittence duration. In Orge stream, organic matter decomposition, fungal activity and macroinvertebrate diversity varied along the flow intermittence gradient, exhibiting higher levels for intermediate flow intermittence, whereas the Ormançon stream maintained high and invariable ecological processes intensity regardless of variations in flow intermittence. Effects of drying on macroinvertebrates functional diversity were observed in the Orge, where highly intermittent stations selected traits adapted to flow intermittence. Functional indicators demonstrated their relevance for characterizing the impact of flow intermittence gradients, supplementing conventional taxonomic indicators. Studies covering a larger number of intermittent streams are needed not only to better characterize and understand their functioning, but also to define reference values that will help improve the environmental management of this ecosystem type that is rapidly increasing in proportion.

Source: Ecological Indicators

DOI: 10.1016/j.ecolind.2026.115517