Rehabilitating seagrass by facilitating recruitment: improving chances for success

Abstract

Attempts to arrest seagrass loss through numerous rehabilitation methods have traditionally produced inconsistent results. On Australia's southern coast, hessian bags made from biodegradable jute fibers show promise for rehabilitating Amphibolis antarctica by facilitating recruitment of seedlings in situ. Testing ways to improve the performance of bags (i.e. increasing seagrass recruitment and establishment) showed that bags with a coarse outer weave of hessian facilitated greater seedling densities (approximately 1700 individuals/m2) than bags with a fine outer weave, but the content of bags (sand vs. sand and rubble mixture) had little effect. Isolated bags facilitated greater longer term densities than bags grouped together, while similar densities were sampled up to 80 m away from a natural meadow. Lastly, bags that had spent less time in situ initially facilitated more recruits than older bags, but longer term (21–32 months) retention was similar among bag ages. Collectively, the results suggest hessian bags can be a relatively simple, cost-effective, and environmentally friendly method for rehabilitating Amphibolis seagrass, with few considerations in their use other than their physical architecture and arrangement (e.g. isolated coarse-weave bags).