Biomonitoring of intermittent rivers and ephemeral streams in Europe: Current practice and priorities to enhance ecological status assessments

Abstract

Intermittent rivers and ephemeral streams (IRES) are common across Europe and dominate some Mediterranean river networks. In all climate zones, IRES support high biodiversity and provide ecosystem services. As dynamic ecosystems that transition between flowing, pool, and dry states, IRES are typically poorly represented in biomonitoring programmes implemented to characterize EU Water Framework Directive ecological status. We report the results of a survey completed by representatives from 20 European countries to identify current challenges to IRES status assessment, examples of best practice, and priorities for future research. We identify five major barriers to effective ecological status classification in IRES: 1. the exclusion of IRES from Water Framework Directive biomonitoring based on their small catchment size; 2. the lack of river typologies that distinguish between contrasting IRES; 3. difficulties in defining the 'reference conditions' that represent unimpacted dynamic ecosystems; 4. classification of IRES ecological status based on lotic communities sampled using methods developed for perennial rivers; and 5. a reliance on taxonomic characterization of local communities. Despite these challenges, we recognize examples of innovative practice that can inform modification of current biomonitoring activity to promote effective IRES status classification. Priorities for future research include reconceptualization of the reference condition approach to accommodate spatiotemporal fluctuations in community composition, and modification of indices of ecosystem health to recognize both taxon-specific sensitivities to intermittence and dispersal abilities, within a landscape context.

Streamlined eco‐engineering approach helps define environmental flows for tropical Andean headwaters

“…Extreme low‐flow conditions (<20% of median annual flow) in managed streams simulated patterns extensively reported for intermittent streams (Datry et al., ; Stubbington et al., ), where habitats such as pools provide, to some extent, favourable conditions between flow releases. Andean streams with unmanaged conditions are known for their high levels of dissolved oxygen and low nutrient concentrations, providing suitable conditions for benthic fauna colonisation (Ríos‐Touma, Encalada, & Prat Fornells, ).…”

Flow intermittency influences the trophic base, but not the overall diversity of alpine stream food webs

“…IRES likely make up at least 50% of the world's waterways (Datry et al 2014), and flow intermittency is further increasing in extent and duration in response to changes in climate and land use (Leigh et al 2016). Despite a continually growing body of research on IRES (Datry et al 2017), substantial knowledge gaps of flow intermittencyecosystem function relationships still exist (Leigh et al 2016, Stubbington et al 2018. In particular, little is known regarding the ecology of intermittent alpine streams, which can experience up to 90% intermittency in fluvial networks (Robinson et al 2016).…”

“…Collection of high-resolution data on flow intermittency is often time and labor intensive (Stubbington et al 2018). Further, gauging stations are most often placed on large, perennial channels, rather than the extensive upper network of low-order streams that are more likely to dry (Meyer et al 2007, Snelder et al 2013.…”

High stream intermittency in an alpine fluvial network: Val Roseg, Switzerland

“…Furthermore, it also can be difficult to assess whether missing gauge data are due to surface‐water drying, malfunction and maintenance, or transition to a lentic state (Oueslati et al ; Stubbington et al ). Many other direct measures (field mapping, aerial photos, remote sensing, citizen science; Fritz et al , Gallart et al , Robinson et al , Spence and Mengistu ) and indirect indicators of intermittency (temperature, modeling, aquatic community structure; Constantz et al , Cid et al , González‐Ferreras and Barquín ) are used, often in combination, to identify the distribution of IRES at finer spatial resolution ( see Stubbington et al ). However, these are largely time, labor, and cost‐intensive for measuring fine‐scale temporal variation in flow intermittency, especially for whole river networks.…”