Mussels are effective cleaners of the water in the Baltic Sea. Each little mollusc filters several litres of water an hour and consumes substances such as nitrogen and phosphorus that would otherwise fuel algae growth in the sea. Since the blue mussel in particular is so common here, it is estimated that all the mussels together filter the entire volume of the Baltic Sea at least once a year. That can be compared with the inflow and outflow at Denmark, where it takes about 20 years to replace the water of the Baltic.

And on top of that, mussels are incredibly beautiful – just think how an opened blue mussel actually forms a heart!