Initial composition and abundance of phytoplankton and microzooplankton.

Top panel: The relative contribution of each of the five main phytoplankton groups in the WAP region to total chlorophyll a in the top 50 m of the water column (WC0–50 m) where seawater and krill were collected for the experimental incubations (HPLC pigment CHEMTAX analysis; % contribution to total chlorophyll a). Bottom panel: Abundance of dominant phytoplankton (cryptophytes, diatoms) and microzooplankton (ciliates) in incubation bottles after a 24-hour acclimation period (T0) in control (no krill added) bottles bubbled with ambient (Amb) and high concentrations of CO2 (Microscopic analysis; cells ml−1). Values are mean±1 SD.