Effects of depth on manual transplantation of the seagrass Amphibolis griffithii (J. M. Black) den Hartog on Success Bank, Western Australia

Abstract

Transplants were established in February and December 1997 to supplement and provide feedback for a mechanical seagrass transplantation programme. A total of 580, 15 cm diameter plugs of Amphibolis griffithii were transplanted to depths of 5, 6, 8 and 10 m with similar energy conditions, and their survival monitored. There was a significant decline in plug survival over the subsequent 14 months. This appears to correlate with the onset of the winter storms in May 1997; the control plugs (seagrass excavated and replanted in the same location) also declined during this period. There was a seasonal decline in stem density in all plugs, with some recovery in the following spring and summer. The decline of plug survival corresponded to large-scale fluctuations in sediment levels across Success Bank. This suggests that, provided the transplants survive hydrodynamic disturbances resulting in sediment level fluctuations, the light climate (up to 10 m depth) does not prevent the survival and growth of seagrass transplants.