Changes in sediment characteristics in the first year of a realigned saltmarsh

Abstract

Saltmarsh restoration is described as a cost-effective response to coastal biodiversity loss and flood management, although, to date such conservation practices yield different characteristics than natural marshes, such as in plant communities and sediment properties. The outcome of these differences is thought to be influenced by the initial conditions set within the first year of marsh re-establishment, which are often overlooked or neglected as part of the restoration process. Therefore, our study aimed to address this gap by examining the spatial and temporal variations in sediment characteristics of a newly (<15 months) realigned saltmarsh in Essex, UK and the effects of previous land use (arable and pasture). Sediment properties (bulk density, nutrients and pH) were sampled monthly from the realigned site as well as from an adjacent reference natural marsh. After 14 months from initial inundation the two realigned marsh regions (arable and pasture) behaved similarly despite different starting points in terms of pH, water content, bulk density and nutrient load. Physical aspects of the realigned sediments (bulk density and water content) matched those of the reference natural marsh within 14 months post-breach in the 0–5 cm depth range. By contrast, the lower depth sediments within realigned sites remained more dense and drier compared to natural marsh sediments. Chemical properties of the realigned sediments matched those of the natural marsh throughout the sediment profile 14 months post-breach. Success of restoration is measured in the ability of the site to provide the desired ecosystem services and short-term recoveries and set goals may not imply long term sustainability as these observed differences may have ramifications for future biological community development and the success of a restoration.