Restoring the seagrass Zostera muelleri with transplants: small cores are as effective as larger plots

Seagrass extent has declined globally, including in New Zealand. Following the success of an initial trial to transplant and re-establish intertidal seagrass at a former site in Whangarei Harbour, a second trial was initiated. This trial aimed to restore seagrass at a more distant former site and tested the efficacy of transplant units ranging in size from small cores (5 or 9 x 0.01 m diameter cores placed within a 0.25 m(2) plot) to larger entire plots (0.25 m(2) or 0.5 m(2)). Seagrass was transplanted in winter when plants were dormant. Plant cover of transplanted and donor plots and light climate at both sites were monitored over a period of four years. All but one of the 24 units survived, and the plants began to spread after 12-18 months to eventually develop patches ranging in size from 5 to 68 m(2). Seagrass recolonised all donor plots completely within 10 months. Results show that small cores and larger plots can both be used successfully to transplant and restore populations of Zostera muelleri with no long-lasting damage to donor meadows. However, use of small cores is recommended to minimise extractions and loss of transplanted material, and to simplify logistics.