Developing seed- and shoot-based restoration approaches for the seagrass, Zostera muelleri

The restoration of seagrass habitats is a relatively young field with several successful restoration attempts highlighting the feasibility of large-scale restoration. Successful restoration of seagrass habitats requires an understanding of the most appropriate techniques to use for the target species and local conditions of restoration sites, however, there are currently limited studies on Zostera muelleri. Here, we conduct field trials to explore the use of seed- and shoot-based restoration approaches for Z. muelleri in Victoria, Australia. We assessed the feasibility of collecting and germinating seeds in the field for restoration purposes and trialed the success of four shoot-based transplanting techniques. We found that seed collections for Z. muelleri were highly successful and scalable, with seed collection rates improving from 489 to 1,939 seeds/hour over 2 years. In addition, in situ seedling germination increased from a maximum of 10.80-25.25% over 2 years. In contrast, shoot-based restoration approaches were more variable, with plants transplanted with their sediment-intact outperforming all bare-rooted approaches. Shoot-based transplanting approaches appear to have more limited application, but may be appropriate for some restoration sites, or used in combination with seeds to achieve the best restoration outcome. Seed-based approaches have the potential to be viable and scalable for Z. muelleri given that large numbers of seeds can be collected and stored for at least 7 months before successfully germinating in the field. However, further studies are required to overcome the seedling survival bottleneck (approximately 4 months from emergence) and further increase in situ germination rates.