Mussels behavior as a tool to measure hydrological stressors

Abstract

Freshwater mussels are considered suitable bioindicators and used in real-time remote monitoring systems to detecting disturbances on ecosystems. One of the most successful methods is the valvometric technique that exploits the Hall sensor to measure the valve gaping behavior of mussels. The duration and frequency of valve opening amplitude and closure can therefore be recorded. These technologies have been used in the past to detect pollutants in the water, whereas studies that address the impact of hydromorphological pressures are still lacking. The main aim of the present study is to assess the influence of flow with sediment transport as well, both in steady and in unsteady (transient) conditions, in four endpoints of mussel's behavior: normal activity, resting, transition and avoidance. To this aim, experiments in laboratory flumes with mussels on a bed made of sands, for varying flow discharges, have been conducted. Results suggest that during transients and in the presence of sediment transport, mussels change their behavior, showing an increase of their valve opening-closure frequencies and amplitudes. These results are encouraging to support the use of mussels as biosensor also in their natural habitat (rivers or lakes) to monitor the occurrences of natural events involving hydro-morphological variations, as floods.