was used to test if oyster bacterial communities were significantly different between oyster species and among sampling times. The R-statistic value describes the extent of similarity between each pair in the ANOSIM analysis with a range of values from zero to one, with values close to unity indicating that the two groups are entirely separate and a zero value indicating that there is no difference between the groups. Similarity percentages (SIMPER) ( Clarke, 1993) analyses were done to determine bacterial community similarity within factors, as well as between factors. Unconstrained ordinations were plotted to graphically illustrate the relationships between oyster bacterial communities using principal coordinate analysis (PCO) ( Gower, 1966). The relative proximity of the points is related to the degree of similarity in the microbial structure.