Rivers have dead zones?

Question

I don't think that a river can have a dead zone, it is always moving , right? so oxygen moves everywhere....Does Danube river have a dead zone? if yes, what is the size of it's dead zone?

Answer 1

A river's dead zone is usually considered the area where it empties into an ocean.  This large influx of organic matter and fresh water creates an area in the ocean where normal aquatic life cannot survive.  They cannot survive due to the low oxygen in that dead zone water.  My sources are very helpful.