Streams and rivers provide important services to humans (e.g., drinking water, food) and therefore preserving their health, or their ecological integrity, should be a societal goal. Ecological integrity is defined by both structural integrity (the good status of communities of aquatic plants, fish, invertebrates, etc.) and functional integrity (the good status of the processes that control fluxes of energy and matter in the ecosystem, such as photosynthesis, organic matter decomposition, etc.). Stream and river bioassessment, however, rarely considers ecosystem functioning even though this is critical because communities and their function not always respond equally to environmental change, and there can be important changes in function without noticeable changes in communities. Among potential indicators of stream and river functional integrity, measurements of organic-matter decomposition and ecosystem metabolism (e.g., oxygen production and consumption through photosynthesis and respiration) are good candidates because they respond to environmental change in a predictable manner and are relatively easy to assess. We have performed a review of studies that used organic-matter decomposition and ecosystem metabolism for stream and river bioassessment since the year 2000, and show that in most occasions (~ 75% studies), these two ecosystem functions perform well at detecting environmental changes such as those resulting from agricultural activities, forestry or urbanization. Interestingly, both functions were sensitive to restoration practices in all studies examined, meaning that they are also effective indicators for detecting whether restoration is having an effect at a given site. Although in Europe stream and river bioassessment relies only on structural indicators (for example, aquatic communities, water quality), functional indicators are already being integrated in stream and river bioassessment in New Zealand and Australia. Given that assessing only structural features may provide an incomplete and potentially misleading picture of stream and river ecological status, incorporating functional indicators is an essential step towards improving their management and conservation.

Read the full study  here:

Ferreira V., Elosegi A., Tiegs S., von Schiller D. & Young R. 2020. Organic-matter decomposition and ecosystem metabolism as tools to assess the functional integrity of streams and rivers – a systematic review. Water 12: 3523

Text written by Verónica Ferreira and edited by Clara Ruiz and Félix Picazo