Non-photosynthetic oxygen production and non-respiratory oxygen uptake in the dark: a theory of oxygen dynamics in plankton communities
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Plankton respiration is commonly measured in terms of oxygen uptake, usually employing the Winkler method, much less commonly the polarographic method. Both methods produce results that can be misinterpreted when H2O2 production and decomposition are ignored. This paper: (1) presents experimental evidence of significant H2O2 involvement during plankton incubation in dark bottles, (2) explains how results differ between the Winkler and polarographic methods in the presence of H2O2, (3) discusses how this difference is clouded by side issues of variability inherent in the Winkler technique and the use of different bottle sizes, and (4) shows that unexpected and variable results of light-/dark-bottle incubations can all be explained by a theory of H2O2 production and decomposition. During an initial period in the dark, when plankton respiration has been poisoned by mercuric chloride or chloroform, O2 increase can be measured with a polarographic oxy‐gen sensor (POS). The trend in O2 changes is linear for several days when only respiration is occurring, but curvilinear when there is concurrent O2 production. O2 production in the dark and H2O2 decomposition are one and the same process. Measurement of oxygen by Winkler analysis and POS produce different results when H2O2 is present because the former method measures oxidizing equivalent while a POS measures O2 pressure. A real difference in results between the two methods is prima facie evidence that H2O2 is involved. The synthesis of this new empirical evidence with diverse knowledge from various fields shows that the common practice of estimating gross community primary production from oxygen changes in light and dark bottles is based on untenable assumptions.
KeywordsOxygen Uptake H2O2 Production Plankton Community Oxygen Production Dark Bottle
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