Effects of different sediment types on the seed germination and seedling growth of tropical seagrass, Enhalus acoroides

In recent decades, natural and anthropogenic disturbances in coastal areas have resulted in a world-wide decline of tropical seagrass meadows. Thus the recovery of seagrass meadow has gained more attention. Therein, the seagrass seed/seedling transplantation is highly regarded due to less destructive of donor seagrass meadows and enhancement of genetic diversity in the restoration seagrass meadows. The sediment type in the planting area is an important factor in determining the rates of seed/seedling transplantation success. However, there is little information of tropical seagrass seed germination and seedling growth responding to the sediment type. To address this gap, we carried out a laboratory incubation experiment using different sediment type (fine sand and coarsegravel sand treatments) for seed germination and seedling growth of tropical seagrass Enhalus acoroides. The result shows that the germination rate and mean time-to-germinate were not significant difference between the fine sand and coarse-gravel sand groups, with the mean values of 96.3% and 3.6 days, and 95.0% and 3.4 days, respectively. The survival rate of germinated E. acoroides seedlings in the fine sand was 97.37%, while it was only 81.58% in the coarsegravel sand group. In addition, the E. acoroides seedling leaf and root lengths and their growth rates were all significantly longer and higher in the fine sand group than the coarse-gravel sand group, respectively. Therefore, the impacts of sediment type on E. acoroides seed germination and time-to-germinate are not significant though coarse-gravel sand has much lower seedling survival rate and seedling growth rate. These results indicates that the fine sand sediment type for E. acoroides seed/seedling transplantation in the tropical seagrass restoration should be chosen as it can promote the seed/seedling transplantation success rate.