Effects of seed burial depth on restoration success of wild-sown and nursery-propagated Thalassia hemprichii seedlings

Seed-based restoration offers a non-destructive approach to restoring threatened seagrass meadows. Here, we explore the use of Thalassia hemprichii seeds and seedlings for restoration by examining the impact of seed burial depths in the aquarium and in the field, and by assessing the benefits of a nursery grow-out period prior to transplantation. In the aquarium, seeds buried at 0 cm and 1 cm had the highest seedling emergence and survival (100% and 98.7%, respectively), which declined with increased burial depth (2.5 cm: 74%, 4 cm: 23.9%). In the field, seeds buried to 1cm had the highest survival and seedling emergence (26%), double the seedling survival at 0 cm burial and nine-fold higher than seeds buried to 4 cm. Following a six-month nursery grow-out, 52% of transplanted seedlings survived after 3-months in the field, compared with 11% survival of seeds from the same collection period, but planted directly in the field at the optimum field burial depth (1 cm). A comparison of effort across the restoration approaches in this study showed sowing seeds directly into the field to a depth of 1 cm provided the best trade-off between planting and propagation effort and subsequent survival at our field site. Nursery propagation and subsequent transplantation required the most effort, cost, and expertise, but produced the highest returns per seed, which may be beneficial when seed stock or the planting window is constrained. These results demonstrate that small changes in planting technique for T. hemprichii can have large impacts on early-stage survival, a key bottleneck in seed-based seagrass restoration, and highlight the need to evaluate trade-offs between yield and effort on a project-by-project basis.

Marine Environmental Research

Marine Environmental Research

221

1879-0291

N/A

N/A

11