Freshwater mussels as a flood early warning system

Abstract

Future climate scenarios predict an increase of extreme events. Thus, understanding how floods impact freshwater ecosystems and their organisms is important for their conservation. Changes in freshwater mussels’ behaviour can be used as an early indicator of environmental disturbances. However, studies that focus on the effect of physical disturbances on freshwater ecosystems related to climate change are lacking. In this sense, the first aim of this work was to perform laboratory experiments in artificial flumes to evaluate the eligibility of mussels’ behaviour as a biomonitoring tool used in real-time remote systems. To this end, we used the valvometric technique (that exploits the Hall sensor) to measure the mussels’ valve gaping behaviour when subjected to different hydrological and sediment transport conditions mimicking the onset of floods. Freshwater mussels promptly reacted to extreme discharge conditions with sediment transport by increasing valve gaping frequencies, shifting their behaviour. After this validation in laboratory conditions, the second objective was to test their valvometric behaviour in the field to improve the reliability of the data and standardize the use of this methodology for its practical application. For this purpose, experiments were performed in a natural river where we built cages and attached the mussels. The preliminary results of this field work confirmed that mussels sharply increase their valve gaping in response to extreme conditions promoted by natural floods. Both laboratory and field experiments suggest that mussels’ behaviour is a suitable indicator of the change of hydrological conditions and can be used as biomonitoring tool in biological early warning system (BEWS).