Recruitment and colonisation of vegetative fragments of Posidonia australis and Posidonia coriacea

Abstract

Vegetative fragment recruitment of both Posidonia australis and Posidonia coriacea was observed on Success Bank, Western Australia, beginning in November 1993 ( n=106). Recruitment of vegetative fragments was defined as attachment to the substrate and subsequent rhizome extension. Rhizome extension occurred in 31% of all recruited P. australis vegetative fragments, yet no extension was detected in recruited P. coriacea vegetative fragments. In shallow water (<9 m), P. australis vegetative fragment recruits extended at an average rate of 0.78±0.02 mm per day, but did not survive for more than 10 months. This extension rate was slightly less than in situ meadow rhizomes of established P. australis plants (1.01±0.19 mm per day) from the same depth. The majority (78%) of deep water (10–12 m) P. australis vegetative fragment recruits survived >10 months, with rhizomes extending at slower rates (0.41±0.02 mm per day) than shallow water recruits. No in situ seagrasses grew at the deep site for direct comparison.