Reproductive properties of Zostera marina and effects of sediment type and burial depth on seed germination and seedling establishment

• Reproductive Z. marina in Shandong peninsula occurred from late March to late August.
• Seed release began in early June and seed production peaked in mid-July.
• Early July was appropriate time for seed collection as then most seeds were viable.
• Sediment type and burial depth affected seed germination and seedling establishment.

The dynamics of reproductive properties of Zostera marina in the Shandong Peninsula was recorded based on field investigations. Influences of sediment type and burial depth on seed germination and seedling establishment were studied in controlled laboratory conditions. In the field, the reproductive stage occurred from late March to late August. The reproductive properties showed obvious seasonal variation and had a significant impact on the cumulative seed production. Seed release began in early June, and the cumulative seed production was 10451 ± 371.0 seeds m−2, while the maximum production in a single week was 2907 ± 258.1 seeds m−2. The seed germination experiment showed significant effects of seed burial depth as well as the interaction between sediment type and burial depth on both seed germination and seedling establishment percentages (p < 0.001). Seeds on the sediment surface or buried to 1 cm could maintain high germination percentages (76 ± 11.5% and 90 ± 1.5%, respectively) regardless of sediment type. With increasing burial depth, germination percentages decreased gradually and were lower than 40% in all sediment types. Only seeds in sand:silt mixtures 2:1 could germinate when the burial depth increased to 5 cm; the earliest germination appeared in the fifth week and the cumulative germination percentage was lower than 3%. Seedling establishment showed a similar trend to seed germination; seeds buried in shallow depths showed a higher seedling establishment percentage, and the maximum value was recorded in seeds that were buried to 1 cm in sand:silt mixtures 2:1 (30.67%).