The free-living Hormosira banksii in Botany Bay, Australia: twenty years on.

Abstract

Hormosira Banksii is the most common fucoid alga on rocky shores in temperate Australasia. It is the only fucoid alga in the region which also exists in free-living populations, and in this is it comparable with the unattached saltmarsh fucoids occurring in the northern hemisphere. The unattached populations of Hormosira are most often associated with mangroves, and the characteristics of such plants have been described from New Zealand (moore 1950, Bergquist 1959) and south eastern Australia (Clarke and Womersley 1981, King 1981). The population that grows amongst the pneumatophores in the Avicennia mangrove communities of southern Botany Bay, Australia, has been described by King (1981). It appears to have been derived from adjacent populations on rocky shores. The characteristics that distinguish the thalli from those of rocky shore populations include the lack of holdfasts, the absence of sexual reproduction, and the compact and highly branched thallus form. Other features regarded as characteristic of unattached fucoids include dwarfed and twisted thalli often with yellowish tips (Norton and Mathieson 1983). King (1981) noted that small thalli were common in the free-living Hormosira but also noted that someplants were about four times larger than those found on rocky shores.