Ecological Indicators (Nov 2021)
Stream drying bioindication in Central Europe: A Biodrought Index accuracy assessment
Abstract
With ongoing climate change and increasing water resource pressures, the knowledge and predictability of stream drying is essential for water management. However, the hydrological data for assessing the flow regime of temporary streams are often non-existent or scarce. The flow regime strongly affects stream ecological functioning and ecosystem processes. A few biological indices have been developed in the past decade to assess community responses to flow intermittency. One of them – the Biodrought Index, used to recognise antecedent stream drying based on benthic invertebrate assemblage composition – was initially intended for deployment in the Czech Republic. Here we report on a test of how reliably this index can be used in Central Europe. We used five independent data sets of macroinvertebrate samples collected during the flowing phase in five countries: Austria, Czech Republic, Germany, Hungary and Slovakia. Altogether 89, 26 and 220 samples were assessed from intermittent, near-perennial and perennial sites, respectively. Each sample was assigned to one of three flow intermittence categories according to the Biodrought Index and then compared with the flow regime recognised by hydrological observations and gauging station data. In most cases, the Biodrought Index clearly reflected the previous flow state and identified streamflow cessation. The misidentification rate between intermittent and perennial samples was very low, ranging from 0% to 6%. Classification rate of correctly recognised samples ranged from 54% to 93% and misclassification rate between near-perennial and perennial/intermittent category was 6% to 46%. Overall, this study confirmed the robustness and the reliability of the Biodrought Index, which proved to be an effective tool in assessing the recent hydrological history of small and medium-sized streams. The index can improve the interpretation of the macroinvertebrate assemblage data collected for ecological status assessment, can help to evaluate the effectiveness of river restoration projects or identify water resource pressures. Hence, we consider the Biodrought Index a useful method for indicating antecedent stream drying in the extensive area of Central Europe and thus helpful in monitoring and managing river ecosystems.
