The Ria de Aveiro is a shallow “bar-built” estuary 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 only connection to the Atlantic Ocean is through a narrow channel 1.3 km in length, 350 m wide and 20 m deep. The bathymetry of the 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. The total fluvial discharge into the lagoon during a tidal cycle is about 1.8 x 106 m3, while the tidal prism is 137 x 106 m3 for maximum spring tide, and 35 x 106 m3 for minimum neap tide. The circulation in the Ria de Aveiro is therefore essentially dominated by tidal forcing. Due to the combined effects of the freshwater discharge and tidal penetration, the Ria de Aveiro exhibits a longitudinal salinity gradient from about 0 in the upper reaches of the channels to about 36 at the bar entrance. The tidal phase lag, relative to the mouth, is in the order of 6 h in the upper reaches of the channels.
Geologically the Ria de Aveiro is a recent feature, formed through the accumulation of marine and riverine sediments during the last 1000 years in a wide and shallow bay, following the flandrian transgression. These mechanisms have not yet attained equilibrium and the present tendency is to silt up. Much of the present-day geomorphology of the Ria has been determined by human intervention directed to counterbalance this silt-up tendency, which culminated in the opening of the present inlet in the central part of the sand bar in the beginning of the 19th century and subsequent consolidation, in order to facilitate tidal flow.
The Ria de Aveiro has a moderately low degree of eutrophication and low overall human influence in comparison to other estuarine environments (Ferreira et al., 2003). The implementation of EU policies with respect to the environment have, furthermore, greatly reduced the discharge of contaminants. There is, however, still substantial contamination in bottom sediments close to contaminant sources and these may become a major source of metals to the water column. The Ria de Aveiro also houses the largest area of contiguous salt marsh in Portugal and one of the largest in Europe in addition to housing important wintering populations of waders.
The main goals of LTER-RAVE are to:
1. Monitor primary productivity and the processes controlling nutrient flows including C, N, P and Si.
2. Develop a whole ecosystem approach to understanding the interaction between biological communities and these processes
3. Collect all available biological, environmental and economic data on the Ria de Aveiro and use these data together with the data collected during this study to monitor temporal changes in biological communities, ecosystem services and environmental conditions
4. Develop an integrated model using data from the previous objectives to simulate long-term scenarios of climate change and their impact on global ecosystem dynamics. The various scenarios will consider changes in the sea level, climate, biogeochemical cycles, and hydrological, physicochemical and biological variables.
5. Quantify the ecological and economic services provided by the Ria de Aveiro and how human activities within and in the vicinity of the estuary are affecting these services.
Ria de Aveiro
Portugal LTER site