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Macrophytes in Estuarine Gradients

Acronym: MEG
Period: November 2004 till 2009
Status: Completed

Thesaurus terms: Estuaries; Hydrodynamics; Seagrass; Water quality
Geographical term: ANE, Europe, Northwest [Marine Regions]

Institutes (6)  Top 

Estuaries are threatened worldwide by increasing human use and alterations, resulting in losses of estuarine areas. Contrastingly, restoration of estuarine gradients and associated nature areas is a rather new policy topic in the Netherlands. Allowance of seawater penetration into freshwater areas provides an option in sea level rise management.

Aquatic macrophytes strongly characterise shallow and relatively sheltered areas in estuaries, and are known to substantially alter hydrogeochemical processes. They act as eco-engineers, and provide important ecosystem services like seabed and shoreline stabilisation and improvement of water quality.

This research aims to construct a coupled model to (1) predict potential macrophyte development in near-invariant estuarine gradients and (2) predict the consequences of macrophyte development on hydrogeochemical processes (eco-engineering). With this model, we will be able to indicate potential habitats of macrophytes in unvegetated sites, and quantify their hydrogeochemical consequences (ecosystem services). This can be applied in areas that are or will be restored with regards to environmental requirements of estuarine macrophytes, like restoration of estuarine gradients, but also improvement of water quality or reduction of disturbances, etc. Secondly, the model can provide a quantification of losses of ecosystem functions in areas where estuarine gradients are threatened. The models will be coupled using an iterative loop reflecting the feedback coupling: macrophytes alter their own environment, which will in turn influence their subsequent development until a new equilibrium has been reached.

Key factors controlling the distribution of macrophytes are largely known and described in growth models.Large datasets and geographical models describing the abiotic environment (hydrology and geochemistry) are present at the participating institutes, as well as in white and grey literature. Also, the effects of macrophytes on morphodynamics and water quality are studied in recent years. However, (1) this information is scattered and ecological information has hardly been integrated in present hydrogeochemical models, (2) interactive effects among different factors controlling macrophyte development have scarcely been investigated, and appear to be of paramount importance for our understanding of ecosystem functioning, (3) information on feedback coupling between macrophytes and their effect on their own habitat will provide us with a model that will have global rather than local applicability.
We will to integrate available information into a single model (MEG), based on three submodels: MEG1, a box model to predict potential macrophyte development in estuarine gradients, MEG2 to predict the effects of macrophytes on hydrogeochemical characteristics, i.e. physical parameters like wave reduction, sediment stabilisation, resulting sediment transport and morphology (MEG 2), and MEG3 to predict water quality (turbidity and nutrients) (MEG3).
In addition, mesocosm research will be carried out to generate lacking information on interactive effects on macrophytes, particularly of nutrients and salinity, and results will be incorporated in MEG.

MEG, linking hydrogeochemical data to ecological information, will be an important new predictive tool for ecological development in estuarine gradients worldwide, and as such provide a scientific basis for future integrated management of coastal areas on a sustainable basis. Macrophytes on either end of the estuarine gradient (marine or freshwater) have been most thoroughly investigated. The partners in this research look forward to comparing methods, and applying them to the estuarine species in the intermediate zone.

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