The Citizen Science Stream Index - a simple and effective citizen science biomonitoring protocol using six key macroinvertebrate indicator taxa

Water quality in many European headwater streams is poor, but monitoring these numerous waterways presents logistical difficulties. Citizen scientists can complement professional biomonitoring, given suitable information and training, but simple, rapid methodologies are preferred for CS initiatives. Here we report on the development and trial of a novel Citizen Science Stream Index, (CSSI), which uses just six macroinvertebrate indicator taxa. A national (Ireland) set of stream macroinvertebrate communities and water quality ratings was interrogated to determine the most suitable CS taxa, based on three key criteria: taxa should be readily identifiable by a non-expert, show a strong negative or positive response to water quality and be numerous and geographically widespread. We derived a scoring system, based on the presence/absence of these six taxa in stream kick samples. The CSSI was validated using macroinvertebrate and water chemistry data sets and trialled by citizen volunteers in 40 different streams. CSSI scores were significantly correlated with UK ASPT scores and the Irish Small Stream Risk Score (SSRS) and showed similar spatial and temporal trends. All biomonitoring metrics were also significantly correlated with water quality. Volunteer CSSI scores were also significantly correlated with ASPT and SSRS values. The CSSI system was therefore a good proxy for more complex multi-taxa biomonitoring protocols. The simple and intuitive nature of the CSSI offers citizens a straightforward way to engage with streams, and obtain useful data on water quality, with minimal training and post-sample verification. Our scheme, based on simple principles, can be readily adapted to other regions.