The controlled reduced tide system (CRT) is a new technique for restoring tidal marshes and is being tested in the Schelde estuary (Belgium). Biogeochemical processes within a CRT were hypothesized to support and improve several estuarine functions such as sediment trapping and nutrient burial. In 2006, the first pilot CRT was implemented in the freshwater zone of the estuary. Fifteen sediment physicochemical descriptors were intensively monitored over 3 years in the newly created CRT and in reference habitats from the adjacent estuary. Soil transformed rapidly in the CRT; in the most frequently flooded zones, the formation of a nutrient-rich estuarine sedimentary substrate contrasted with the estuarine sand flats where shear stress is sustained by coastal squeeze. The temporal dynamics of the sediment descriptors were investigated to identify key processes involved in the flooding of the CRT sediment. Although many processes were specific to the CRT, both reference and CRT sediment characteristics experienced similar long-term oscillations. However, despite such variations, successful CRT nutrient trapping and fine particles burial were demonstrated. This study proves that the CRT, in accordance with restoration goals, can restore ecological functions in impacted estuaries. In addition, the results highlight the complex timing of abiotic patterns in intertidal sediments. |
