Fig 1. Diagram of experimental configuration.

A: Ambient air at 400 ppm CO₂ was bubbled into four 2-L phytoplankton culture bottles for the control pCO₂ treatment, and ambient air mixed with pure CO₂ to a final concentration of 1,000 ppm CO₂ was bubbled into another four 2-L phytoplankton culture bottles for the high-pCO₂ treatment; medium was delivered to each bottle from pre-bubbled 20-L media reservoirs. B: Each semi-continuous culture bottle had ports for medium inflow, gas inflow, and media/gas outflow.