Use of bio-containers from seagrass wrack with nursery planting to improve the eco-sustainability of coastal habitat restoration.

Traditional revegetation techniques employed to restore seagrass meadows and coastal dunes have recently been criticized for their impact on donor populations as well as for the installation of plant anchoring structures made of non-biodegradable or not natural materials in recipient habitats. To improve the ecological sustainability of restoration practices, a novel plantable biodegradable container made of beach-cast seagrass wrack and a bio-based polymer was produced. The long-term performance of two seagrasses, Cymodocea nodosa and Zostera noltei, and two dune plants, Euphorbia paralias and Thinopyrum junceum, grown in nurseries from seeds using the bio-container or a non-biodegradable container of equal size/form made of a conventional plastic (control) was also examined. In addition, the development of bio-container-raised C. nodosa plants in the field was compared to that of plants removed from control containers at the installation and anchored with a traditional system. The bio-container degraded slowly in seawater and in sand and lost its functionality after about three years. In nurseries, all the tested species grown in bio-containers performed as well as, or better than, those raised in non-biodegradable ones. Six months after transplanting into the field, 80% of the C. nodosa nursery-raised plants installed with their bio-container have colonized the surrounding substrate while most of those planted with the traditional system was lost. These results indicate that the new bio-container may support plant growth, and it may also provide protection and anchorage to plants in the field. The use of this bio-container in combination with nursery techniques could improve the environmental sustainability of coastal restoration interventions by providing large plant stocks from seed, thus reducing the impact of collection on donor populations. This approach would also limit the introduction of extraneous materials in recipient habitats and offer an opportunity for valorizing seagrass beach-cast material.