6200ha of seagrass has been lost from the Adelaide coast since 1949. This has caused 100,000m3 of sand to be deposited on Adelaide beaches per year, and increased coastal erosion due to increased longshore movement of sand. Additionally, the loss of this habitat has affected many important fish species and overall biodiversity of flora and fauna in the region.In response to this loss, improvements to waste and storm-water systems were implemented, resulting in some natural recolonisation in deeper waters. To investigate the possiblity of assisted recolonisation, a large scale rehabilitation trial was undertaken in 2006 in which hessian sandbags were placed over 1 hectare adjacent to an existing Amphibolis antarctica meadow. The trial aimed to understand the effect of distance from nearest meadow on recruitment success and plant length. Hessian bags were filled with sand and covered in jute weave. 1000 units were dropped over a 100m x 100m square, with one edge beginning 10m inside the meadow. Recruitment was monitored using video transects. The study found that there was no significant effect of distance from meadow edge on recruitment density or plant length. Overall, the proportion of bags supporting one or more Amphibolis plants was 65% after 4 and 8 months, increasing to 87% after 13 months.

Seagrass

Method: Hybrid

Seagrass species: Posidonia australis

Planting density: 1/1m2

Hybrid structure: Hessian bags filled with sand and wrapped in coarse jute weave