Mussels are disappearing from the Thames and growing smaller – and it's partly because the river is cleaner

The population of River Thames freshwater mussels has declined by almost 95% since 1964. BadPixma/Shutterstock

Freshwater ecosystems, including rivers, are home to 10% of all known animal species. Yet at the same time, they are losing their species diversity faster than any other ecosystem type globally. Because species of animals respond to different threats in various ways, it makes it difficult to assess the health of these river systems.

But the population status of species such as freshwater mussels can reveal wider trends in the ecosystem. Freshwater mussels live in riverbeds and feed by filtering algae and other organic particles from the water. As they burrow into the riverbed and remain largely stationary, they are exposed to many of the stressors threatening rivers and are therefore a useful indicator the health of the river in which they live.