Abstract
In the current context of global change, erosion of biodiversity is a major challenge of the twenty-first century. The short-term consequences reside in weather events of extreme violence. On the functioning of ecosystems, they are difficult to predict, but the structure of communities will be impacted by the environment and changes in species distribution. The advent of NGS generates many sequence data to establish a more complete description of the constituent communities metaborcoding biodiversity. To estimate the impact of disturbances on metazoan communities belonging to eelgrass beds (Zostera nolti) in two localities, the Bassin d'Arcachon and Etang de Thau, we adapted a protocol metabarcoding based on high-throughput sequencing. Sediment samples were collected in triplicate along a disturbance gradient to minimize the dominance of larger organisms sieve fractions by corers (1mm, 500 .mu.m and 250 .mu.m). Two molecular markers mitochondrial (cytochrome oxidase I) and nuclear (18S small subunit ribosomal RNA) were used. Bioinformatics procedure selected analysis is based on the Qiime pipeline under linux, using local databases to optimize blast procedures. The molecular barcoding represents a major advance in environmental community studies, in comparison sorting fauna. The description of biodiversity is dependent on the quality of the reference database, the two markers chosen represents a compromise because they exhibit different affinities with major taxa constituent communities. The results showed a modification of the alpha diversity that has a similar profile to that expected on the assumption of "intermediate disturbance", but complementarity COI and 18S markers reveal finer replacement communities accompanying impact beyond a certain threshold. This tilting of communities is more clearly demonstrated by co-occurrence network analysis Operational Taxonomic Units (MOTU).