Standard Presentation Australian Marine Sciences Association Annual Meeting 2023

Planting mangrove seedlings instead of seeds in concrete planters can increase restoration success (#305)

Amanda R Hsiung 1 , Stephen E Swearer 1 , Rebecca L Morris 1
  1. National Centre for Coasts and Climate, School of BioSciences, The University of Melbourne, Parkville, VIC 3010, Australia

Mangrove habitats are effective coastal defences as they protect shorelines from erosion. In Australia, hybrid approaches have been used for mangrove restoration at sites with unsuitable conditions (i.e. high wave energy) for natural regeneration and/or successful direct planting. But even with the use of built structures, there are other challenges to restoration that need to be addressed due to changes in environmental conditions following mangrove loss. Concrete mangrove planters were deployed at three sites facing coastal erosion in Victoria: Grantville, Lang Lang and Altona. Avicennia marina seeds were planted inside and at adjacent shorelines, and their survival was monitored for a year. The effectiveness of the planters in increasing A. marina survival varied across the sites and it was hypothesised that insufficient protection and high wrack abundance affected mangrove survival. Two life stages of A. marina were subsequently planted: seeds and 1-year-old seedlings, and their survival was monitored over two years. Seedlings planted had higher survival, especially at Altona. Planting seedlings ensures that non-viable seeds are avoided. Additionally, seedlings have longer roots for stabilisation and are less affected by wrack smothering. Mangrove restoration methods should be site-specific to target the environmental conditions contributing to low mangrove survival.