Fig 4. Mass balances of silica, carbon, nitrogen, and phosphorus.

Solid and dashed lines indicate temporal net changes (Δ values) of the silica, carbon, nitrogen, and phosphorus (Si, C, N, and P) pools and of their respective net community production as average values of ambient and high CO₂ mesocosms respectively (see Table 2 for a detailed symbol description). DIC is only included at ambient CO₂ (grey, dotted line), lacking correction for CO₂ air-sea gas exchange (see Sect. 3.2). Roman numbers denote the different phases of the experiment. Percentages indicate the approximate discrepancy between net community production and inorganic nutrient consumption during Phases III and IV.