Seed germination and recolonisation of Zostera capricorni after grazing by dugongs

Abstract

A seagrass meadow dominated by Zostera capricorni Aschers. was intensively grazed by dugongs (Dugong dugon Müller) between November 1992 and January 1993, leaving a bare sand surface. In less than a year densities had returned to pre-grazing levels with shoot densities of around 11,000 m−2 by August 1993. Recovery of the seagrass appears to have been augmented by a high incidence of sexual reproduction. The flowering season was between August and March, with a peak in December (1219 ± 338.8 flowering shoots m−2; 11.8% of all shoots). Seeds were found in the sediment throughout the year with least in late winter and early spring (August to November). Germinating seeds were found in the sediment throughout the year with the highest number and proportion in May (86 ± 30.5 m−2 and 22%). Seed production was considerably higher at this site than has been found in previous studies of Z. capricorni.