Oyster Microcystis aeruginosa feeding experiments, Lafayette-Louisiana, 2021-2022

To determine how the presence of the potentially harmful cyanobacteria M. aeruginosa affects oyster feeding, we quantified clearance rates, pseudofeces production, and pseudofeces composition across two feeding experiments conducted with a non-toxic strain. The first experiment consisted of bialgal feeding experiments where single oysters were fed treatments consisting of 1) only M. aeruginosa, 2) only the diatom Thalassiosira pseudonana, or 3) a 50/50 mix of the two species. To quantify effects of M. aeruginosa on oyster feeding under more environmentally relevant conditions — which includes numerous phytoplankton prey options and the presence of inorganic particles — a second feeding experiment was conducted using a natural phytoplankton community collected from a local estuary and oyster habitat. This natural community was then used to create two treatments, 1) an amended treatment where non-toxic M. aeruginosa was added, and 2) a natural treatment where only M. aeruginosa growth medium without cells was added.