Different types of environments resulting from the dynamic equilibrium between the sea, the river and freshwater can be found in the Baix Ter plain. The interaction between the sea, the river and the sediments it carries has given rise to a wide variety of ecosystems, with very subtle variations in the duration of floods, depth, salinity, nutrient content or type of substrate. The variety of environments and the diversity of organisms that can be found in them are two of the most important ecological aspects of the area. A description of the main aquatic ecosystems found in the Baix Ter follow.

- marshlands and coastal lagoons
- coastal freshwater ponds
- springs
- inland temporary ponds
- river Ter estuary
- strongly humanized aquatic atmospheres