Mondego Estuary
The Mondego River drains a basin of approximately 6670 Km2 and its valley is considerably steep in upstream sections, forming a large alluvial plain consisting of good agricultural land in downstream areas. Since the 1960s, the Mondego catchment area underwent a large scale morphological modification, involving the construction of stone walls, to regulate the river water flow and enlarge harbor facilities, and water reservoirs to control floods, improve the uses of water resources, and produce electric power, which modified the riverbed topography and changed the system hydrodynamics. The river contributes presently with a high anthropogenic loading of nutrients and several chemicals into its relatively small estuary (1600 ha, splitting in two arms separated by an island in the terminal part), causing eutrophication. Besides, the estuary - Western coast of Portugal - North Atlantic Ocean Eco-region - supports industrial activities, salt-works, and aquaculture farms, and is the location of Figueira da Foz, a harbour and a centre of seasonal touristic activity. A comprehensive study on the Mondego estuary environmental quality has been carried out during the last two decades, focusing on water quality, hydraulics and sediments dynamics, plankton communities (phyto, zoo, and ichtyoplankton), the term evolution of the benthic communities (intertidal and subtidal), and the changes in macrophytes’ beds (Zostera noltei) and green macroalgae distribution in relation to morphological alterations.
Ecology of Mondego estuary
The environment is characterized by a great variety of flora and fauna, which includes the presence of:
- Phytoplankton community;
- Zooplankton community; the Copepoda is the main holoplanktonic group and Acartia tonsa revealed to be the more abundant taxa. Other holoplanktonic important groups are Cladocera and Siphonophora.
- Macroalgae and Macrophytes (mainly Zostera meadows); survey will provide information on macroalgae and macrophytes as ecological indicators of ecological status.
- Benthic invertebrates; the most frequent species found in the intertidal area of the southern arm of the Mondego estuary are the polychaetes Alkmaria romijni, Hediste diversicolor, Heteromastus filiformis and Streblospio shrubsolii, the amphipod Melita palmate, the decapod Carcinus maenas, the isopod Cyathura carinata, the gastropoding ulvae and the bivalves Cerastoderma edule and Scrobicularia plana; while, the most frequent species found in the subtidal samples of the Mondego estuary are the polychaetes Glycera convoluta, Hediste diversicolor and Nephtys hombergii, the decapod Crangon crangon, the isopods Cyathura carinata and Lekanesphaera levii, the gastropod Peringia ulvae and the bivalves Cerastoderma edule and Tellina tenuis.
- Fish community; it is characterized by the presence of important commercial species as the eel
(Anguilla anguilla), the bream (Diplodus vulgaris), the sole (Solea solea), the flat fish (Platichthys flesus) or the seabass (Dicentrarchus labrax).
- Shorebirds; the Mondego estuary is an important ornithological site, where it is possible to admire water birds including: white-faced cormorant, egret, heron, flamingo, fish eagle, sandpiper, knight of Italy, rock curlew, common winch, dark gull, herring gull, herring gull, common tern. Among the rarities it is possible to observe: small flamingo, reddish duck, yellow thigh, striped beaked gull, herring gull. Morraceira Island is used by various species of water birds as a refuge from the high seas, such as flamingos (often very aboundant), egrets and herons. The island is located in the middle of the estuary and is mainly composed of salt marshes, many of which are still active. The island can be accessed via the bridge over the Mondego river, and from the road it is already possible to see many birds.
Socio-economical value
The Mondego estuary has an important regional socio-economic value as it provides various ecosystem services for the population. It is the basis of some fundamental activities for economic development, such as agriculture (mainly rice cultivation), industry, supports the merchant harbour, fishing, aquaculture, tourism and salt production. Indeed, the Mondego River estuary constitutes one of the main salt production factories in Portugal that are still active.
Figueira da Foz salt factories are located in the estuary of the Mondego River and extend on the south side of the river and on Morraceira Island. The salt factories are made up of small units with a large number of rooms, connected by a dense network of canals. These salt pans were one of the main economic activities of Figuiera da Foz, today its historical and cultural heritage. A particular feature is the existence of the typical salt warehouses, wooden constructions, based on a platform, with a capacity to store 150 to 200 tons of salt (currently, some of them are in ruins). To safeguard this important heritage, a museum has been created in one of the salt factories in Figueira da Foz (dedicated to the production of salt, housed in a wooden house in the middle of the salt flats along the Mondego river), a pedestrian path (3 km long) and a boat ride. These three options allow you to learn more about this ancient practice, which has characterized the landscape of Figueira for many years and which today wants to be preserved.
Furthermore, the Mondego river basin is one of the Portuguese basins with a greater use of water resources, especially in the agricultural and hydroelectric sector, which highlights the system that produces an annual average of 360 GWh, which regulates the volumes of water for public supply in some counties of the Lower Mondego and the irrigation of the Lower Mondego.
In Figueira da Foz, in the Mondego estuary, there is a small harbour, also used by researchers to enter the estuary and carry out campaigns to collect samples to analyse in the laboratory.
Mondego waters are also used to practise various sports such as sailing, rowing and canoeing.