Summary

Outbreaks of a strain of Caulerpa taxifolia were first discovered in NSW in April 2000 and the seaweed is now present in 10 estuaries, growing primarily on soft sediments at depths of 0.5 – 9 metres. C. taxifolia is often associated with, and is thought to threaten, native seagrasses, but there is little published evidence of such negative impacts. Ongoing research in NSW is investigating the interactions between native seagrasses (Zostera capricorni and Posidonia australis) and C. taxifolia. Multiple approaches are being used, including regular mapping of the extent of infestations within estuaries, detailed surveys of the abundance of seagrass and C. taxifolia at scales of 1 – 50 m, and small-scale experimental transplantations of C. taxifolia at the scale of 1 – 10 m (done in areas where C. taxifolia was already abundant). No obvious effects of C. taxifolia on seagrass have been detected after more than 3 years of mapping and experimentation, but the behaviour of C. taxifolia seems to differ greatly among estuaries.