Biofilm monitoring as a tool to assess the efficiency of artificial reefs as substrates: Toward 3D printed reefs

International audience; Habitat destruction is one of the main causes of the decline of biodiversity and of fishery resources in the marine environment. An artificial reef (AR) could be a tool for protecting or restoring these habitats and their declining biodiversity, and also help to enhance sustainable fisheries. The goal is to design non-polluting structures that best mimic the complexity of natural habitats in order to improve their service to the community. To date, the assessment of reef performance has been mostly focused on fish assemblages and species of ecological and/or socio-economic interest, and has disregarded the biofilm communities that determine the first level of an AR’s trophic network. In this work, we used biofilm formation to compare the quality of substrates used as building parts for an AR, in order to optimize an eco-friendly material that will be used to design a new generation of ARs produced by giant 3D printers. The structure of the photosynthetic communities has been identified using pigment biomarkers and their production of exudates has been analysed. These polymeric substances were quantified in terms of total sugar and protein concentrations. They were further analysed in terms of amino acid content. We found no significant differences between the micro-algae communities developed on the different substrates. These photosynthetic communities were mainly composed of diatoms, prasinophytes, haptophytes, and dinoflagellates. However, we showed that the material for ARs is crucial for biofilm development, especially with regard to its secretions of sugar. The choice of an appropriate substrate for AR construction is thus of particular importance since biofilm secretions determine the organic substrate on which sessile macro-organisms will settle.