The Ria de Aveiro is a shallow coastal lagoon on the NW coast of Portugal. It is c. 45 km in length (NNE-SSW), 10 km wide and in a spring tide covers an area of approximately 83 km2 and 66 km2 of wetland at high water and low water, respectively. The Southern European coastal lagoon is a Nature 2000 site that covers the downstream area of the Vouga river until the Northeast Atlantic Ocean, encompassing all types of aquatic realms from freshwaters to marine waters (Lillebø et al., 2019), one of the largest continuous salt marshes in Europe.

Ria de Aveiro consists of three main channels which radiate from the mouth with several branches, islands and mudflats: the Mira channel runs to the south and is narrow and shallow; the S. Jacinto - Ovar channel lies to the north and is wide and deep in its southern part but changes northwards, forming secondary narrow and shallow channels and bays; the Main channel bifurcates leading to the Ílhavo channel to the south and to the Espinheiro chanel, through which the major river, the Vouga, flows. 

Due to its ecological complexity and diversity, it attracts very different types of socio-economic activities (Dolbeth et al., 2016). Despite the pressures it sustains, this system is recognized as model of biodiversity and balance between man activities and wildlife. Such natural richness is protected under several environmental policies, and regulatory competencies are shared by many institutions.

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The lagoon area is also a Long Term Ecological Research (LTER) site (http://www.lter-europe.net/). link