A comparison of short-term sediment deposition between natural and transplanted saltmarsh after saltmarsh restoration in the Eden Estuary (Scotland)

Abstract

Background: The fringe saltmarsh in the Eden Estuary is suffering severe erosion and its die-back will expose the shoreline to an increase in wave and tidal energy, especially given rising sea levels.

Aims: To investigate the effect of vegetative transplants on saltmarsh sedimentation, the present study aimed to compare short-term sediment deposition and accretion in transplanted sites of Bolboschoenus maritimus and Puccinellia maritima with those in natural stands of these species and with upper unvegetated mudflats. The effect of tidal height and wind direction on sediment deposition in the different systems was also studied.

Methods: Sediment deposited each day was collected on pre-weighed filter papers placed on the sediment surface and the sediment accreted each month was weighed in relation to the zero bed level by using a bar placed across marker poles.

Results: Older transplants of B. maritimus retained significantly higher quantities of sediment than natural P. maritima or the upper mudflats, but had similar amounts to that deposited in natural B. maritimus. Deposition rates in younger transplants were found to be similar to those on the upper mudflats. Sediment surface elevation in natural P. maritima remained constant throughout the year, but increased in all other sites during the summer. The upper mudflat was the only site to erode during winter. A significant positive association was found between tide height and sediment deposition, while winds from the south-east were associated with significantly more deposition than winds from the south-west.

Conclusions: These findings suggest that saltmarsh restoration using vegetative transplants can enhance sedimentation in eroded fringe saltmarsh. This strategy deserves further investigation since it may provide a sustainable management option in the face of rising sea levels.

Keywords:

• Eden Estuary
• erosion
• marsh restoration
• saltmarsh
• sea level rise
• sedimentation

Acknowledgements

We are grateful to the Fife Environment Trust and the School of Biology, University of St Andrews, for their joint Ph.D. scholarship funding to CM. We are also indebted to past and present members of the Sediment Ecology Research Group, University of St Andrews, for stimulating discussions and helpful comments.