Fig. 5. Net ecosystem autotrophy drives a CO₂ sink in most of the studied African lakes.

Variations in several African tropical lakes of the air-water gradient of the pCO₂ (ΔpCO₂) as a function of the ratio of aquatic pelagic primary production (P) and community respiration (R) (A) and the air-water CO₂ flux (FCO₂) as a function of NEP (B). P/R > 1 and NEP > 0 correspond to net autotrophy at the community level and is, in most cases, associated with being a sink of atmospheric CO₂ (ΔpCO₂ < 0, FCO₂ < 0). For lakes where multiple measurements were made, the symbol shows the median (n indicates the number of measurements).