Study has focused on bacteria, archea and eukaryota found in the sediment (beneath tentacles), along the digestive tract and in faeces of three sea cucumber species in five stations across two coral reefs of Reunion Island (French Island, Southern Indian Ocean) during three consecutive seasons. PCR primers used were: 16S rRNA V4-V5 region: 515F : 5-GTYCCAGCMGCCGCGGTAA-3 928R : 5-CCCCGYCAATTCMTTTRAGT-3 16S rRNA Archea: 519F : 5'-CAGCMGCCGCGGTAA-3' 915R : 5'-GTGCTCCCCCGCCAATTCCT-3' and COI: m1COIintF-XT : 5'-GGWACWGGWTGAACWGTWTAYCCYCC-3' jgHCO2198 : 5'-TAIACYTCIGGRTGICCRAARAAYCA-3'.