Propagating eelgrass (Zostera marina) from cuttings in land-sea combination systems: a novel method to improve the sustainability of seagrass restoration

The combination of a land-based system and natural habitat can propagate donor plants from cuttings for use in seagrass restoration projects; however, the appropriate period for land-based cultivation is unclear. Eelgrass (Zostera marina) cuttings were cultivated under different combinations of land-based (0, 3, 6, 9, and 12 weeks) and natural habitat cultivation for 12 weeks. We measured survivorship, growth, productivity, leaf pigmentation, and carbohydrate concentration in eelgrass. Return on investment (defined as the number of ramets of Z. marina returned through input cultivation costs in the seagrass cultivation process) analysis suggested that the optimal period of land-based cultivation for the propagation of Z. marina is 3.1-3.8 weeks. The ramet frequency of Z. marina exposed to a combination of land-based cultivation (3 weeks) and natural habitat cultivation (9 weeks) was 1.4 times higher than that of plants cultivated in natural habitats for 12 weeks. The promotional effect of the combination of land-based and natural habitat cultivation on Z. marina mainly depended on the increase in chlorophyll content and the accumulation and synthesis of nonstructural carbohydrates. The soluble sugar content of Z. marina leaves exposed to a combination of land-based cultivation (3 weeks) and natural habitat cultivation (9 weeks) was 1.5 times higher than that of plants cultivated in natural habitats for 12 weeks. These results indicated that implementation of a controlled plant cultivation system and process to acquire abundant donor plants. This can help provide valuable data for the development of efficient artificial propagation technologies for Z. marina.