2.3. Commercial oyster tank experiments
To determine whether invertebrate species used for aquaculture in Tomales Bay were impacted by microcystin, we purchased oysters from a commercial aquaculture vendor in Tomales Bay for
immediate testing. Additional oysters were purchased from the same vendor for use in tank experiments at a later date. The standard distribution protocol for the supplier includes placing oysters in a tank of fresh filtered flowing water for five days prior to release for public purchase and consumption. Additionally, oysters were cultivated and harvested under 28500–28519.5 of the California State Health and Safety Code.
Oysters purchased for immediate testing were processed following methods described above for mussels. Oysters purchased subsequently for tank experimentation were acclimated in constantly
flowing filtered seawater for 24 h before experimentation. Three control oysters were collected and processed before the start of the trials, and the remaining oysters were separated
equally into 3 tanks. Microcystis was again collected from Pinto Lake, CA mixed with saline water (Instant Ocean, Spectrum Brand, Virginia) and administered to 3 separate tanks with a concentration of 7.71 mg/L microcystin. Cell counts were collected and analyzed as described above. Oysters in all 3 tanks were exposed to microcystin for 24 h, after which they were placed in a water table with constantly flowing filtered seawater for the remainder of the trial. Oysters were sampled and processed as described in 2.1.