Key words. Coastal ecosystems, transplanting trials, compensatory restoration, Posidonia
Introduction. Seagrasses are flowering plants that form extensive underwater meadows, transforming bare sandy areas into complex 3-dimensional habitats for a diverse faunal community. They provide a wide range of ecosystem services including nutrient cycling, carbon sequestration, and coastal stabilization. Once impacted, seagrass meadows can take decades to recover.
The need for seagrass restoration is mainly driven by loss of seagrass due to human activities including ocean discharges and coastal developments, although changing ocean conditions (warming temperatures and increasing acidity) and sea-level rise now provide additional challenges.
Figure 1. Posidonia australis showing spreading and merging shoots from what were initially only single planting units (see inset).
Cockburn Sound project. In 2003, the Seagrass Research and Rehabilitation Plan (SRRP) was established to meet stringent environmental management conditions for two separate industrial development projects in Cockburn Sound, Western Australia. Both projects, Cockburn Cement Ltd and the state Department of Commerce, impacted upon seagrass ecosystems.
The SRRP was aimed at developing and implementing seagrass restoration procedures that are economically feasible and environmentally sustainable. The collaborative project team was coordinated by BMT Oceanica and included researchers from Murdoch University, The University of Western Australia, Edith Cowan University, the Botanic Gardens and Parks Authority, environmental consultants and a marine engineering firm.
Works and their results. Implementing the SRRP involved a range of experimental transplantings of the seagrass Posidonia australis (a slow-growing meadow-forming species).
The transplant trials resulted in good health and high survival rates of transplanted shoots. This showed that meadows can be restored and thus are likely to develop and return to the same ecological functions as natural meadows.
In this case, donor material was harvested from a site that was to be destroyed as part of the permitted development. In other cases, donor material has been harvested from meadows that have demonstrated varying levels of recovery, with a number of years required for recovery depending on the intensity of harvesting. The project resulted in site-specific solutions as well as generic technical guidelines for manual transplantation to restoration sites from donor sites.
Lessons and limitations. The main lessons for practice to date are:
- While the results of this project are encouraging, the challenge of achieving biological diversity in seagrass meadows, particularly to the equivalence of a natural seagrass meadow, has not yet been demonstrated.
- The scale of this particular project is still small (3.2 Ha) relative to the amount of restoration required. Focus needs to be on research into how such projects can be scaled-up. Seed-based restoration may be more appropriate for some species (including Posidonia).
- Selection of a restoration site is a strong factor contributing to the success of transplanted material (i.e. the likelihood of success if higher where seagrass was present before).
Contact. Dr Jennifer Verduin, lecturer, Murdoch University , Tel: +61 8 93606412/0404489385; Email: j.verduin@murdoch.edu.au
Also see:
EMR project summary – report on the seagrass transplanting trials:
EMR Project Summaries 