Use of seagrass wrack in restoring disturbed Australian saltmarshes

Authors

  • M. G. Chapman,

  • D. E. Roberts


  • M. G. Chapman is from the Centre for Research on Ecological Impacts of Coastal Cities, Marine Ecology Laboratories (A11, University of Sydney, NSW 2006, Australia) and D. E. Roberts is from BIO-ANALYSIS: Marine, Estuarine & Freshwater Ecology, 7 Berrys Head Road, Narara, NSW 2250, Australia. Tel. +61-2 9351 4778. Email: gee@bio.usyd.edu.au).

Abstract

Summary  Saltmarshes are threatened in many parts of the world, considered wastelands rather than valued as wetlands. This is particularly true in urbanized parts of Australia. Approximately 85% of saltmarsh has been lost or severely damaged in the Tuggerah Lakes of the Central Coast of New South Wales, Australia. Wrack (rotting vegetation) can promote diversity of saltmarshes, by shading soil and reducing physical stress and/or by providing nutrients to nutrient-poor soil. In many parts of the world, wrack derives from the saltmarsh plants. On the shores of the Tuggerah Lakes, large amounts of seagrass wrack (with varying amounts of macro-algae), are stranded along the shoreline and in the remaining saltmarshes. This is perceived to reduce public amenity and have no ecological value. Thus, the local council is under pressure to remove wrack. This experimental study examined the influence of wrack on cover and diversity of saltmarsh and provided preliminary data on changes to organic matter and benthos in the sediment. On average, there was a rapid increase in biomass of the dominant plant, Sarcocornia quinqueflora, in experimental areas where wrack was added, although the response was patchy, but there was no change in diversity over 22 months. There were limited changes to benthos, but no changes to nutrients in the sediment in wracked compared to unwracked treatments. Nevertheless, increased biomass in dominant species may reduce physical stress for other smaller saltmarsh plants. This study is part of a programme examining the interaction between the persistence and growth of saltmarshes and recycling of wrack in the lakes. The ultimate aim is to develop ecologically and economically sound plans of management for an increasingly urbanized area of the NSW coast.

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