In order to achieve a fully natural seagrass meadow long term, it is envisaged to produce the artificial structures from material that disintegrates completely after a given time frame, i.e. when the natural seagrass is fully established and the artificial structures are no longer required.

The screening of materials that could possibly be used as artificial seagrass (ASG) is orientated towards ecological and hydrodynamic parameters measured in natural seagrass meadows, such as growth patterns, wave/current forces or ecosystem services. This data is collected in work package (WP) 3 and 4.
For the material choice, one also needs to distinguish between the different parts of the entire ASG system, which have different requirements. The following initial material options have been identified:

• Biodegradable plastics that functionally and optically resemble seagrass
• Natural materials, fibres and fabrics
• A combination of natural materials and biodegradable plastics

Materials will be characterised with respect to their suitability in terms of degradation, technical and mechanical properties and usable production methods. This evaluation of existing materials will inform requirements for material development or adaptation to achieve the necessary properties for each ASG element as defined by WP4.

A key property for all materials used for the ASG is biodegradation under marine conditions, which is currently unknown for most commercially available biodegradable materials (either natural or bioplastic). Respirometric measurements in bottles will be carried out to estimate the biodegradation behaviour of the different materials in a comparative study. The same tests are required for the potentially suitable natural materials. While it is known that these materials disintegrate, the respective time frames and associated changes in material properties have not yet been evaluated.

The degradation experiments will also consider the chemical composition of residues and potential environmental impacts of intermediate stages of disintegration. This assessment will ensure that utilised bioplastics will not be harmful to marine fauna at any stage of the ASG life cycle and evaluate the effect of non-native natural materials (e.g. coconut mesh) on local ecosystems.

Existing bioplastics can be processed with conventional techniques (e.g. foil extrusion, injection moulding, 3D printing). In order to make newly developed materials within this project commercially viable, their suitability for such production methods will be assessed in this task. This is of particular relevance if additives made from natural materials are used or composites of natural fibres and bioplastic coating are developed. The methods applied and tested within this task will strongly depend on selected materials in this WP and will therefore be defined during the course of the project.