Morphology, flowering and seed production of Zostera capricorni Aschers. in subtropical Australia

The vegetative morphology, flowering characteristics, seed production, and seed distribution in the sediment of the seagrass Zostera capricorni Aschers. were studied for 18 months by monthly sampling. Three seagrass zones were studied. In each of these zones there was a different morphological type of Z. capricorni: small, dense plants in the midshore zone; large, sparse plants in the offshore zone; medium size and medium density plants in the inshore zone. The distribution of seeds in the sediment was also studied in bare areas adjacent to these vegetated zones. Flowering lasted for 8 months, from September to April, with the highest percentage of shoots flowering in September and November. Flowering lasted longest in the midshore zone (7 months), compared with the inshore (3 months) and offshore (4 months) zones. The density of flowering shoots was also higher in the midshore zone (341 ± 14.0 flowering shoots m) than in the inshore (4 ± 1.0) or offshore (12 ± 4.0) zones. Both the mean number of spathes per shoot (3.1 ± 0.07), and the number of female flowers per spathe (4.8 ± 0.20) did not vary significantly between zones. However, there were more male flowers per spathe in the offshore (10.5 ± 1.55) than in the inshore (5.6 ± 1.60) or midshore (5.4 ± 0.88) zones. Although most seeds were found in the midshore zone during the flowering season (177m ± 28.4), some seeds remained in the sediment for 4 months after seed production had ceased. Few seeds were found outside the seagrass beds, of these most were in bare areas long-shore of the seagrass