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Intertidal morphology change following Spartina anglica introduction, Tamar Estuary, Tasmania

Citation

Sheehan, MR and Ellison, JC, Intertidal morphology change following Spartina anglica introduction, Tamar Estuary, Tasmania, Estuarine, Coastal and Shelf Science, 149 pp. 24-37. ISSN 0272-7714 (2014) [Refereed Article]


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Licensed under Creative Commons Attribution 3.0 Unported (CC BY 3.0) http://creativecommons.org/licenses/by/3.0/

DOI: doi:10.1016/j.ecss.2014.07.006

Abstract

The surface morphology and sediment characteristics of introduced Spartina anglica marshes of the Tamar Estuary were analysed using a combination of spatial mapping, land-based topographical surveys, sediment coring and identification of the pre-introduction surface. Such a morphological investigation of estuarine change following Spartina introduction has not been attempted elsewhere before. A difference was found between marshes in upper and lower estuary. Surface topography of Type-1 marshes of the upper estuary was found to be independent of the pre-Spartina surface morphology, with deeper vertical development and exhibiting a flat to slightly concave upper marsh, a convex ridge in the outer mid marsh, and a relatively steeply graded convex lower marsh. Type-2 marshes of the lower estuary were thinner in vertical development, and with surface topography dictated by the underlying pre-Spartina surface. The difference was found to be due to variations in environmental conditions in sediment supply and wave/current exposure between the two regions rather being an indication of relative maturity. The seaward edge of marshes was found to be 0.5 m lower at the seaward end of the Tamar relative to the landward, reflecting tidal amplification up this confined estuary. While Spartina marshes are accretionary, surveys demonstrated retreat of the seaward margins throughout the estuary over the past 17 years, and the development of erosional scarps in Type-1 marshes. Spatial mapping identified 374 ha of S. anglica infestation within the Tamar Estuary, with Type-1 marshes occupying 240 ha and Type-2 marshes occupying 134 ha. Topographic profiles and stratigraphic data were used to estimate total sediment volumes trapped by Spartina in the Tamar Estuary, finding approximately 1,193,441 m3 of material to have been trapped beneath Spartina since its introduction in 1947, of which between 14 and 28% has been Spartina-derived organic matter.

Item Details

Item Type:Refereed Article
Keywords:marsh geomorphology, Spartina infestation, saltmarsh, elevation, erosion, sedimentation rates, Tamar Estuary, Tasmania, Australia
Research Division:Environmental Sciences
Research Group:Environmental Science and Management
Research Field:Environmental Science and Management not elsewhere classified
Objective Division:Environment
Objective Group:Ecosystem Assessment and Management
Objective Field:Ecosystem Assessment and Management of Coastal and Estuarine Environments
Author:Sheehan, MR (Mr Matthew Sheehan)
Author:Ellison, JC (Dr Joanna Ellison)
ID Code:93256
Year Published:2014
Funding Support:Australian Research Council (LP0214145)
Web of Science® Times Cited:7
Deposited By:Geography and Environmental Studies
Deposited On:2014-07-22
Last Modified:2017-10-31
Downloads:174 View Download Statistics

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