Ria de Aveiro
The diversity of habitats contained within the Ria is the reason for its enormous ecological wealth. The water provides a habitat for a wide variety of fish. Full of countless varieties of seaweed, it is also an important source of food for certain birds. The uniform-looking marshland is home to a profuse biological life. Intersected by canals and full of islands, it has its own quite characteristic appearance.
Crustaceans and molluscs can be found in the silt and mud deposits revealed at low tide, whilst countless birds are to be seen concentrated on the salt flats. In the farmland surrounding much of the lagoon area, where rice and corn are grown, reeds and rushes, alders, poplars and willows provide shelter for a sizeable bird population. Ponds and ditches are inhabited by numerous frogs and toads, whilst the less conspicuous watercourses are inhabited by otters.
Besides providing an important natural barrier holding back the sea´s advance, the sand dunes are also the home to a number of specific plant communities.
Nowadays, the Ria de Aveiro extends from Ovar to Mira. It is very shallow and there are several watercourses that flow into it, most notably the River Vouga. It is separated from the sea by a long line of sand dunes, of varying width, interrupted only by an artificial bar built in the 19th century. The delta has four main arms - Ovar, Murtosa, Vagos and Mira - and the lagoon has several islets dotted around it.