For each experiment, 96 animals were used. Four exposure tanks were filled with 20 L of filtered 18 °C seawater or ASW plus algal cultures and submergible circulating pumps (Petco Animal Supplies. Inc., San Diego, CA) were added. Animals were divided into two groups, natural microbiota and artificial V. parahaemolyticus exposure, and placed into the corresponding tanks. Oysters in the V. parahaemolyticus group were placed into tanks containing approximately 105 CFU/ml of V. parahaemolyticus, while the natural microbiota group received an equivalent amount of 1% NaCl, and were held in these tanks for 18 h. Following the 18 h exposure, the natural microbiota animals were divided into four tanks, two HS and two control tanks. The V. parahaemolyticus animals were also divided into four HS and four control groups. These experiments were completed in the summer and in the fall.