Ecosystem Service Assessment of TIDE Estuaries

In the Scheldt (Figure 29), provisioning services show a low supply in freshwater and oligohaline zones. However, food provision supply is very low (less than 1% of scale). Low scores for food provision, were attributed since high levels of pollution prevent consumption of fish and filter feeders from the estuary. However, historically as well as potentially, this supply could thus be higher than shown here.
The increase in supply scores of provision of water and regulating functions for water quantity, as well as the higher proportions of deep and moderately deep subtidal habitats towards the mouth provoke an increase in supply of these services, while decreases in most other regulation services (regulation of extreme events and water quality) and habitat services are observed. Supply by marsh habitat is very low in the polyhaline zone. This is caused by the low surface of this habitat, as the supply does not vary much (see section 5.2).
The same holds for tidal flat habitat in the oligohaline and freshwater zone, and shallow subtidal habitat in all zones. Supply scores are high (see section 5.2), but due to low relative surfaces, the contribution to overall ecosystem service delivery is relatively low.

In the Weser (Figure 31), the overall contribution of tidal flat habitat to ecosystem service supply is remarkably high in the mesohaline and polyhaline zone. This is caused by the high proportional surface and the relatively high potential supply scores of this habitat.
The same holds for marsh habitat in the freshwater and oligohaline zone. Provisioning services are quite equally supplied along the estuarine gradient. The supply of supporting services is high and also quite stable along the estuarine gradient.
Water quality regulation and regulation of disturbance services are doing less in the meso- and polyhaline zone, since the proportion of marsh habitat is very low.

In the Elbe (Figure 32), the contribution of marsh habitat to ES supply decreases towards the mouth in favor of tidal flat habitat, as can be seen from for instance climate regulation and flood water storage services. This decrease is mainly driven by the difference in relative surface.
Provisioning services, such as water for industrial use and water for navigation, are mainly supplied in fresh and oligohaline zone, as the port activities are located in the more upstream area. Supporting services are mainly provided by intertidal flats and marshes, while subtidal habitats are more important for provisioning and water quantity regulating services.

In the Humber (Figure 33), the very low proportion of tidal flats and even lower for marshes in fresh and oligohaline zones yields a clearly different picture for the Humber. In the fresh water zone, shallow subtidal habitats are very important, while the deeper habitats increase importance towards the mouth.