Seagrass rehabilitation: successful transplants and evaluation of methods at different spatial scales

Seagrass (Zostera muelleri Irmisch ex. Aschers) was historically prolific in Whangarei Harbour, New Zealand, but has since declined. Over two years we compared the survival of mid-intertidal zone transplants (18 x 0.25 m(2) plots) from a remnant meadow to a former site using three methods: (1) intact `sods', (2) unanchored `sprigs' and (3) sprigs amongst `mats' of artificial plants. Before and after transplant, we quantified plant cover in all plots, and in transects across the wider intertidal zone. We also measured plant biomass, irradiance and water quality at each site. We found that sods and sprigs were equally effective with plant cover increased from <1 to 63%, but mats were ultimately not successful. Cover across the wider transplant site increased from 10% to 46% (biomass from 58 to 321 g m(-2)). Donor plots regenerated within 9 months. This study shows that Z. muelleri can be rehabilitated by transplant upon reinstatement of suitable growing conditions at former sites.