The river mussel, like all freshwater mussels, has an important ecological function in flowing waters through its filtering activity.
One mussel can filter 3 to 4 litres of water per hour. The filtered volume per day is about 85 litres.
Healthy populations consist of 50 to 100 mussels per m2 river bed. This results in a filtering effort of 7000 litres per day. Populated areas of this density can take up several hundred metres. The mussels are therefore able to filter the whole water body over short distances.
Their enormous filtering effort has additional effects on flowing waters:
Undigested particles are deposited on the river bed. These particles provide food for water insects and crustaceans who will consequently increase in numbers. An increasing availability of prey results in growing numbers of fishes including the hosts of the river mussel.
The substrates on the river bed are cleaned and rearranged by the mussels as they anchor to the substrate by the foot and by the movement of young mussels through the gravel beds. Fishes that spawn only in clean river beds profit from this cleansing mechanism.
The mussel shell in itself provides a habitat to many organisms.
Large quantities of nutrients are extracted by the mussels and stored in the mussel’s body. Long-lived species such as the river- and freshwater pearl mussel safe these nutrients over long periods of time and only slowly rerelease them into the water body.
In future years, drinking water will increasingly be produced through ultrafiltration of river water. The mussel’s cleaning activity will reduce the expenses. The mussels provide this service 24 hours a day, 365 days a year- without remuneration. It is us, as humans, that depend on clean drinking water.
Additionally, the river mussel is an indicator for healthy rivers and streams. Water bodies that harbour these mussels are generally in a good condition and have an intact fauna and flora (fish stock, invertebrate numbers, water plants).
Healthy mussels= healthy rivers= healthy humans