Mesocosms (600 L) were deployed at the Southern Ocean Time Series (SOTS) in Austral late summer during a high nutrient, low chlorophyll period. One mesocosm represented control, present-day conditions (high nutrients/low temperature/low pCO2/low Fe/low irradiance), while the other was amended to represent a projected 2100 scenario (low nutrients/high temperature/high pCO2/high Fe/high irradiance). Approximately 2 L were filtered from the mesocosms onto 5 µm filters at Days 0, 2, 4, and 7 of the incubation.