The potential for perimarine wetlands as an ecohydrological and phytotechnological management tool in the Guadiana estuary, Portugal

Climate and human impact on terrestrial sediment flux, nutrient and pollutant delivery to the coastal zone in the Algarve can be clearly demonstrated with both past and recent examples. A Holocene period of high sediment input, supporting a depositional coastal response to relative sea-level rise, has now given way to a period of coastal retreat where increased damming of rivers has led to reduced river flow and terrestrial sediment input. These changes in water and sediment budget are coupled with increased nutrient and pollutant influx associated with agriculture and industrial/urban development. Solutions to these problems may only be addressed through integrated river basin management, and with ecohydrological principles playing a critical role in the development and routine use of sustainable management techniques. Whilst riparian wetlands and saltmarshes are recognised as ecohydrological management tools with which to regulate hydrology, sedimentation, nutrient status and pollutant sequestration and the conservation of biodiversity, the same is not true of perimarine wetlands that occupy the transition zone between catchment and sea. Evidence from Holocene examples of estuarine and back-barrier perimarine wetlands in the UK suggests that they are well adjusted to the conditions of high relative sea-level rise (3e6 mmyr 1) and low terrestrial sediment supply. Whilst Holocene examples in Portugal are sparse, the present conditions of reduced sediment input due to damming and enhanced relative sea-level rise due to Greenhouse warming now makes perimarine wetlands a viable coastal management option. Here, the benefits and practical aspects of perimarine wetland development are considered with a view to establishing a demonstration pilot project in the Guadiana