Seed size affects germination and seedling survival in the seagrass Zostera nigricaulis

The seagrass Zostera nigricaulis is a common nearshore seagrass in southern Australia yet little is known about its reproductive biology. In Port Phillip Bay seed morphology varies across the bay but is not linked to seed... [ view full abstract ]

The seagrass Zostera nigricaulis is a common nearshore seagrass in southern Australia yet little is known about its reproductive biology. In Port Phillip Bay seed morphology varies across the bay but is not linked to seed production. Consistently larger and heavier seeds were sampled at Blairgowrie than both Point Henry and Swan Bay while Edwards Point had intermediate sized seeds. The implications of varying seed size on seed viability, germination, energy stores and seedling success were investigated using an experimental approach. Germination was greater and persisted longer at sites with larger and intermediate sized seeds (Blairgowrie, Edwards Point) than those with smaller seeds (Point Henry, Swan Bay). After germination, seedlings from sites with large seeds survived for longer than sites that had small seed. These results show seed size has a clear effect on germination success and survival. Variations in size across sites may affect the ability of seagrass to regenerate or represent adaptation to variations in environmental conditions across Port Phillip Bay.