In what type of water do mussels suffocate?

Mussels are marine creatures that typically thrive in salty water, which contains a higher concentration of salt than fresh water. In freshwater environments, mussels lack the salinity necessary for their respiratory system to function effectively. They use gills to extract oxygen from the water, and when placed in freshwater, their gills can become overwhelmed, leading to suffocation due to the inability to process the lower salt concentration they are ill-equipped to handle. Therefore, fresh water is not only unsuitable for their survival but can also lead to their decline or death, as mussels are adapted to brackish or saline environments.

The other types of water mentioned can also affect mussels but in different ways. Salty water is their natural habitat; brackish water is a mix of salt and fresh water that can potentially support them, though in lower concentrations of salinity. Polluted water may harm them but does not inherently lead to suffocation, unless the pollution affects oxygen levels. Thus, fresh water is the correct context for understanding how mussels can suffocate.