Mussel survey reveals alarming degradation of River Thames ecosystem since the 1960s

(Image: Pixabay CC0) Scientists replicated a 1964 River Thames survey and found that mussel numbers have declined by almost 95%, with one species - the depressed river mussel - completely gone. This dramatic decline in native mussel populations is very worrying, and we are not sure what's driving it David Aldridge The detailed study measured the change in size and number of all species of mussel in a stretch of the River Thames near Reading between 1964 and 2020. The results were striking: not only had native populations severely declined, but the mussels that remained were much smaller for their age - reflecting slower growth. Mussels are important in freshwater ecosystems because they filter the water and remove algae. As filter feeders they are exposed to everything in the water, and this makes them a valuable indicator of ecosystem health. Mussel shells also provide places for other aquatic species to live. -Mussels are a great indicator of the health of the river ecosystem.