ZMT - Leibniz Zentrum für Marine Tropenforschung

Abstract:
Seagrass ecosystems support marine biodiversity, sequester carbon, and provide key ecosystem services such as coastal protection and the provision of nursery habitat for species of fisheries importance. Despite their value, they continue to decline globally due to coastal development, eutrophication, sedimentation, and climate change. These pressures are also affecting seagrass habitats in Mauritius, prompting a restoration initiative led by local stakeholders and the NGO Reef Conservation.

Environmental DNA or eDNA - genetic material shed by organisms into their surroundings and recovered from environmental samples such as water or sediment - is increasingly used as a non-invasive tool to monitor biodiversity and ecosystem change. In this study, eDNA-based monitoring accompanies a pilot restoration project involving seagrass transplantation, with the aim of tracking responses in fish and invertebrate communities over time.

Here, I will present baseline data collected prior to restoration from three sites in Mauritius: Mon Choisy, Bel Ombre, and Roches Noires. Sampling was conducted in both summer and winter. At each site, five habitat types were targeted—intact seagrass meadow, bare sand, coral patches, river mouth, and channel to the open ocean. Water and sediment samples were analyzed using metabarcoding of the 12S and COI marker regions, sequenced on the Illumina MiSeq platform. Sequence data were processed using a custom R pipeline based on the DADA2 denoising approach to infer amplicon sequence variants (ASVs).

I will show preliminary results for fish communities, including biodiversity metrics and patterns of community composition across habitats and sites. These baseline data establish the analytical framework for evaluating ecological responses in the upcoming post-restoration surveys (3, 6, 12 and 18 months).