LTER-ESTUARIES - Portugal

Basic Information

Site Name: 

LTER-ESTUARIES

Site Code: 

LTER_EU_PT_010

Country (Site Location): 

Portugal

LTER Member Network: 

Subsite Name(s): 

Contact: Site Manager: 

General Site Description: 

3M_RECITAL - MINHO, MONDEGO, AND MIRA ESTUARIES observatory: Long term vaRiation of ECOLOGICAL sTAtus as a response to naturaL and human induced changes. Implications for management and restoration. The Minho River estuary is located in the western Iberian margin (SW Europe), in the border region between the Minho (north of Portugal) and Galicia (Spain) regions. It is classified as a mesotidal estuary, covering a total area of 23 km2. The estuary has a great socio-economic importance, providing goods and services to about 80,000 of persons. It has also a high ecological value, mainly due to its large diversity of habitats and biodiversity (it is included in NATURA 2000; it is classified as a “Zona de Protecção Especial para Aves” (ZEP), an “Important Bird Area” (IBA) and is a CORINE Biotope). The high productivity of this estuary makes it a refuge place for nursery and feeding of marine species, essential to ecosystem functioning. The Minho estuary is still relatively low impacted by anthropogenic activities, however, in the last decades, the environmental pressures and impacts have been increasing, with the most important at the present being: physical and hydrological alterations mainly due to the construction of dams and other facilities to support human activities (e.g. fluvial transport of people and goods, touristic activities, etc); the presence of non-native (exotic) invasive species that have been contributed to the decline of several native species, including some with high economic and conservational interest; and organic and chemical contamination produced or increased by anthropogenic activities (industrial, urban and agricultural sources) still found in low concentrations in water, sediments and organisms but with a general increasing trend over the years; and alterations resulting from global climate changes.This ecosystem has been intensively studied, especially in the last two decades, in relation to hydromorphological characteristics, water quality, communities diversity and functioning, populations health, pollution, among other aspects. However, more knowledge is still needed on environmental chemical contamination and on the effects of complex mixtures of those pollutants in wild populations, communities and ecosystem functioning. In addition, more attention should be given to alterations resulting from global climate changes, in particular in relation to extreme events (e.g. heat waves, floods) and interactions between pollution, invasive species, and abiotic factors variation. Knowledge on plants and microorganisms (especially pathogens and parasits) is lacking. Mondego estuary site is located in the 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. 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 harbour 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. 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. The Mira estuary is a small system (2 km2) located at the Southwestern coast of Portugal that extends between Vila Nova de Milfontes at the mouth and Odemira at its upper limit. It is a narrow entrenched system, with a length of more than 40 km and a mean depth of about 6 m. Saline variability is higher in the middle estuary and sediments are usually dominated by mud and/or fine sand, except in both ends of the system where coarse sediment particles predominate. Near the river mouth presents ecologically important seagrass beds of Zostera marina and Zostera noltii in the subtidal and intertidal areas, respectively. Given the knowledge already available for fishes, benthic macroinvertebrates and saltmarshes communities in the Mira estuary, these are the biologic groups that will be studied with more detail in order to monitor their evolution and assess the hypothetic influence of climatic change and human activities in such evolution. In addition, zooplankton studies will be performed to investigate the impact of the hydromedusae exotic invader Blackfordia virginica in the different compartments of the Mira estuary ecosystem. It is usually considered a well preserved system due to reduced human population and industry. It has high conservation status because the entire estuary is included in a nature protected area (Parque Natural do Sudoeste Alentejano e Costa Vicentina) limiting fishing activities that currently are not allowed. The major threat to this ecosystem is the increasing touristic pressure in all the southwestern coast of Portugal, which may have serious implications to the estuarine water quality. Moreover, several fish farms were installed and agriculture (mainly rice fields) and forestry activities (mainly eucalyptus plantations) occupy an important extension of the water margins. The upstream estuarine areas show a slight contamination by heavy metals due to previous mineral extraction activities in the river basin. Several studies have been conducted in the estuary since the 1980’s. Little information is available for phytoplankton and macroalgae but data about saltmarshes and seagrass beds are much more abundant. Zooplankton data is also scarce but has increased in recent years, particularly with studies on the exotic invasive species Blackfordia virginica. Meiofauna was only studied in Zostera beds but benthic macroinvertebrates and fishes have been studied in more detail along the entire estuarine gradient. Nevertheless, investigation of modifications in these communities related with climate change, human activities and introduction of exotic species must proceed.

UUID: 

664177a4-a21a-4f59-9601-00909e275868
General Characteristics, Purpose, History

Site Status: 

existing

Year Site Established: 

2011

Size : 

4 530.00ha

Purpose of Site : 

Hydromorphological changes, physicochemical parameters and biological communities are basic targets of any estuarine long-term ecological research plan, reflecting the system’s response to natural and anthropogenic stress. Physical disturbances are normally associated with hydrodynamic processes that alter the sediment erosion and depositional cycles and the freshwater flow variability is also a major factor influencing temporal and spatial changes in estuarine physical, chemical and biological conditions, particularly in rivers with strong seasonal regime. In addition to the physical washout effect, strong salinity changes associated to river discharge fluctuations also constitute an important controling factor, which may be substantially influenced by water flow regulation by dams. Likewise, natural phenomena such as storms, floods and droughts can also generate regenerative or degenerative processes, which can cause over or underestimation of the human pressures effects in short-time scales. Three estuaries - Minho, Mondego, and Mira - have been selected as targets for this LTER project because they have already been monitored for long periods and are eventually the most comprehensively studied Portuguese transitional waters ecosystems. The Minho is an international river in the West Iberian Coast, more than 300 Km long, which drains a basin of 17.080 Km2, with a mean flow higher than 300 m3 s– 1, presenting a mesotidal partially mixed estuary, with a maximum width of 2 Km. During high floods it tends towards a salt wedge estuary, with the influence of spring tides extending for about 40 Km upstream. The estuary, which is still relatively low impacted by human activities, has high socio-economic importance, providing goods and services to 80.000 people, and high ecological value, presenting large diversity of habitats and biodiversity (included in Natura 2000; “Zona de Protecção Especial para Aves” (ZEP); Important Bird Area (IBA); CORINE Biotope). Its biological communities have been studied at least since the 40s. However, regular and quantitative studies published in international journals took place mostly in the last two decades, mainly focusing on the benthic macroinvertebrates, namely mollusks, and fish communities. Illustrative publications addressing the most relevant aspects: Antunes et al., 1994; Antunes and Weber, 1996; Cabral et al., 2007; Guimarães et al., 2009; Sousa et al., 2005 ; 2006; 2007a;b; 2008 a; b; c; d; e; Vasconcelos et al., 2009). 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 harbour 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 noltii) and green macroalgae distribution in relation to morphological alterations. Illustrative publications addressing the most relevant aspects: Cardoso et al., 2004; Dolbet et al., 2003; Lopes et al., 2005, Marques et al., 1997; 2003; Martins et al, 2001; Patrício & Marques, 2006; Patrício et al., 2009; Teixeira et al., 2008; in press). The Mira estuary, located in the south-west coast of Portugal, is a narrow entrenched system, with a length of more than 40 km and a mean depth of about 6 m. Until 2007 near the river mouth the estuary presented ecologically important macrophytes’ beds in the intertidal and shallow subtidal areas, which during 2008 collapsed due to unknown causes. Despite this, this estuary is considered well preserved, namely because the river basin has low human population densities and scarce industry, although some of its areas show a slight contamination by heavy metals, probably related to rice cultivation in its upper and middle reaches. In general, the system exhibits minor hydromorphological changes, mainly built for irrigation purposes, and touristic developpment appears presently to be the major threat, which is related to the fact that the Mira estuary is entirely included in a nature protected area (Parque Natural do Sudoeste Alentejano e Costa Vicentina). The Mira estuary has been monitored for the physicochemical characteristics and biological communities, namely the fishes’ community, since the 1980s. Illustrative publications addressing the most relevant aspects: Adão, 2004; Adão et al, 2009; Andrade, 1986; Almeida, 1988; Chainho et al., 2008; Costa et al., 1994; 2008; Marques & Bellan-Santini, 1987). A comprehensive scientific data base on these three estuaries is already available, which allows assessing the effects of both natural and anthropogenic pressures over time on the ecosystems.

History of Site: 

In estuaries, hydromorphological changes, physicochemical parameters and biological communities reflect the systems’ long-term response to natural and anthropogenic stress. Physical disturbances are usually associated with hydrodynamic processes, altering the sediment erosion and depositional cycles, and freshwater flows variability may also be a major factor influencing temporal and spatial changes in physical, chemical and biological conditions. Moreover, strong salinity changes associated to river discharge fluctuations also constitute an important controling factor, which may be substantially influenced by dams’ construction. Likewise, natural phenomena such as storms, floods and droughts can also generate regenerative or degenerative processes, determining over or underestimation of the human pressures effects in short-time scales. Three estuaries - Minho, Mondego, and Mira - have been selected as targets for this LTER project because they have already been monitored for almost two decades, being eventually the most comprehensively studied Portuguese transitional waters ecosystems. The rationale of proposing an L-TER project focusing on these three estuarine systems is to understand the ongoing processes and their evolution under the combined effects of human pressure and climate change, helping in providing answers regarding their sustainable use and management. Estuaries are part of our natural capital, and their sustainable use may be seen from two clearly opposite positions. Weak sustainability holds that utility must be maintained over intergenerational time scales, assuming that natural capital and man-made capital are substitutes within specific production processes. As a result, weak sustainability accepts that the natural capital can be depleted, unless its utility declines over time. On the contrary, strong sustainability states that the natural capital and man-made capital have to be viewed as complementary. Therefore, we should preserve the whole stock of natural capital for present and future generations in the long run. In any case, uncertainties and change are a key question, which makes the systems’ resilience a critical factor with regard to the economic goods and services supply and the maintenance of ecological goods and services. This implies dealing with problems such as: a) losses of habitats and species diversity, b) decrease in habitats size and heterogeneity, c) decrease of many species populations size and changes in their dynamics and distribution, d) habitat fragmentation and increased vulnerability of the remaining isolated pockets; e) decrease of economic goods and services naturally provided by ecosystems. Regarding the systems’ resilience, at least two meanings can be distinguished. The first, engineering resilience, is defined as the time required for a system to return to an equilibrium point following a disturbance event, or system´s recovery. The second, ecological resilience, is defined as the capacity to absorb shocks and still maintain “function”, and can be seen much more as renewal, regeneration, or re-organization following disturbance than as system’s recovery. Establising the relation between critical natural capital and ecological resilience requires information on ecosystem’s function to estimate environmental criticality, i.e. the state in which the system’s carrying capacity is exceeded. Linking these ecological concepts and the management framework is essential to understand, manipulate and manage estuarine systems, and the data to approach such problematics can only be provided by L-TER programmes. In our case, data comparison, integration, and interpretation, regarding present and past events in the three systems, will be complemented with new data acquisition to provide a) better knowledge on ongoing processes and changes, and b) management recommendations.

Research Topics: 

Parameters: 

Photos
  • LTER Estuaries Sites Location
Geographic

Coordinates: 

Latitude: 41.869700000000
Longitude: -8.864980000000