As the need for seagrass restoration increases, so does the reliance on wild stock to replenish depleted populations. Seed-based restoration offers a non-destructive approach to support seagrass recovery. However, seedling establishment success is often low, with high losses associated with water movement, predation, and germination failure. Focusing on a key tropical species, Thalassia hemprichii, we trialed seed planting over a depth gradient, from the sediment surface to 4 cm below, in both controlled aquaria and in cleared areas within an established tropical seagrass meadow.
While surface seeds in aquaria showed 100% survival, a 1 cm burial depth had 98% survival and produced healthier and more productive seedlings. In the field, surface-scattered seeds saw high losses, while 1 cm burial doubled seedling survival compared to surface seeds and increased survival sevenfold compared to 4 cm burial.
This study is the first exploration of the effect of seed burial on aquaria growth and field-based seed restoration for Thalassia hemprichii. It highlights the impact small changes to planting technique and environmental conditions can have on seedling survival when considering best practice for large-scale restoration of this ecologically significant tropical seagrass species.