SUSTAINABLE ESTUARINE ZONE MANAGEMENT FOR CONTROL OF EUTROPHICATION, TOXIC BLOOMS, INVASIVE SPECIES AND CONSERVATION OF BIODIVERSITY (GUADIANA ESTUARY, PORTUGAL)

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Updated: 15/12/2025
SUSTAINABLE ESTUARINE ZONE MANAGEMENT FOR CONTROL OF EUTROPHICATION, TOXIC BLOOMS, INVASIVE SPECIES AND CONSERVATION OF BIODIVERSITY (GUADIANA ESTUARY, PORTUGAL)

Project Overview

Guadiana River Basin is the 4th largest basin in the Iberian Peninsula: 83% in Spain and 17% in Portugal. | There exists 1824 dams in the basin. The Guadiana estuary and the coastal areas are affected by the biggest one called the Alqueva dam. It modified the hydrological regime of the estuary and also its ecological functions reducing the ecosystem service of water regulation. | There are three main protected areas in Guadiana estuary and its floodplains: RAMSAR site, National Reserve, Special Protection Zone (ZPE), Important Bird Area.

Conserve Process NO
Enhance Process YES
Apply Complementary YES

Ecosystem Services

Provisioning

  • Provisioning Services are ecosystem services that describe the material or energy outputs from ecosystems. They include food, water and other resources.
  • Food: Ecosystems provide the conditions for growing food. Food comes principally from managed agro-ecosystems but marine and freshwater systems or forests also provide food for human consumption. Wild foods from forests are often underestimated.

Regulating

  • Regulating Services are the services that ecosystems provide by acting as regulators eg. regulating the quality of air and soil or by providing flood and disease control.
  • Moderation of extreme events: Extreme weather events or natural hazards include floods, storms, tsunamis, avalanches and landslides. Ecosystems and living organisms create buffers against natural disasters, thereby preventing possible damage. For example, wetlands can soak up flood water whilst trees can stabilize slopes. Coral reefs and mangroves help protect coastlines from storm damage.

Habitat / Supporting

  • Ecosystem services "that are necessary for the production of all other ecosystem services". These include services such as nutrient recycling, primary production and soil formation.
  • Habitats for species: Habitats provide everything that an individual plant or animal needs to survive: food; water; and shelter. Each ecosystem provides different habitats that can be essential for a species’ lifecycle. Migratory species including birds, fish, mammals and insects all depend upon different ecosystems during their movements.
  • Maintenance of genetic diversity: Genetic diversity is the variety of genes between and within species populations. Genetic diversity distinguishes different breeds or races from each other thus providing the basis for locally well-adapted cultivars and a gene pool for further developing commercial crops and livestock. Some habitats have an exceptionally high number of species which makes them more genetically diverse than others and are known as ‘biodiversity hotspots’.

Cultural

  • Cultural Services corresponds nonmaterial benefits people obtain from ecosystems through spiritual enrichment, cognitive development, reflection, recreation, and aesthetic experiences.

Major Issues

Risk of eutrophication and harmful algal blooms

Risk of eutrophication and harmful algal blooms

The Alqueva dam

The Alqueva dam

Loss of saltmarsh (loss of nursery functions)

Loss of saltmarsh (loss of nursery functions)

Coastal erosion

Coastal erosion

Loss of biodiversity due to changes in

Loss of biodiversity due to changes in salinity spatial distribution and colonization of alien species

EH Engineering Solutions

Use of two species of bivalves and

Use of two species of bivalves and saltmarsh plants as indication of water quality (fig. 1).

Release of freshwater pulses from the reservoir

Release of freshwater pulses from the reservoir to control the risks of harmful algal blooms.

Project Activities

  • Monitoring biota and water quality in estuarine areas.
  • Analysis of the role of salt marsh plants as buffer vegetation.
  • Control of the risks of eutrophication.
  • Academic research (ICCE) and academic training course (Erasmus Mundus Master of Science in Ecohydrology).

Expected Outcomes

Adapt and restore the ecological functions of estuaries and coastal areas impacted by dams and climatic changes.

Latest Results

Modelling simulations indicate that a discharge of 50 m³/s every day during critical periods, such as summer/autumn, could be enough to avoid cyanobacteria blooms (L. Chicharo et al, 2006). | The Guadiana estuary is expected to be strongly impacted by climatic changes in the next decades (M.A. Chicharo et al, 2009).

Social-Ecological System

Integrated view of principles, objectives, stakeholders and methodology.

Ecohydrology Principles and Solutions

Hydrological Quantification
  • Quantification of the hydrological processes at catchment scale and mapping the impacts | Distribution of ecosystems and their relevant processes (ex: metabolism=water and nutrient uptake and retention; biomass production) | Ecological engineering (integration, dual regulation and biotechnologies in catchment scale for enhancement of ecological potential)
Ecological Identification
Ecological Engineering & Nature-based Solutions
  • Use of two species of bivalves and saltmarsh plants as indication of water quality (fig. 1). | Release of freshwater pulses from the reservoir to control the risks of harmful algal blooms.

Objectives

EH Objectives
Water 3/5
Biodiversity 3/5
Services 5/5
Resilience 5/5
Cultural Heritage 0/5
Project Objectives
  • Discuss trade off between water allocation for agriculture and hydroelectric power production against sustainability of estuarine ecosystems and coastal services.

Key Stakeholders

Researchers (ICCE, University of Algarve). Major industries. Protected areas representatives. Hydroelectric power station at the Alqueva dam. EU Water Framework Directive.

Methodology

  • Quantification of river flows, residence time and productivity on estuarine and coastal ecological functioning and services.