『Abstract
　A coupled photochemical-ecosystem model has been developed to simulate the early Archean biosphere. The model incorporates kinetic and nutrient limitation on biological productivity, along with constraints imposed by metabolic thermodynamics. We have used this model to predict the biogenic CH4 flux and net primary productivity (NPP) of the marine biosphere prior to the advent of oxygenic photosynthesis. Organisms considered include chemotrophic and organotrophic methanogens, H2-, H2S-, and Fe-using anoxygenic phototrophs, S-reducing bacteria, CO-using acetogens, and fermentative bacteria.
　CH4 production and NPP in our model are limited by the downward flux of H2, CO, S8, and H2S through the atmosphere-ocean interface and by the upwelling rate of Fe²⁺ from the deep oceans. For reasonable estimates of the supply rates of these compounds, we find that the biogenic CH4 flux should have ranged from approximately 1/3 to 2.5 times the modern CH4 flux. In the anoxic Archean atmosphere, this would have produced CH4 concentrations of 100 ppmv to as much as 35 000 ppmv (3.5％), depending on the rate at which hydrogen escaped to space. Recent calculations indicating that hydrogen escape was slow favour the higher CH4 concentrations. Calculated NPP is lower than in the modern oceans by a factor of at least 40. In our model, H2-based metabolism is moderately more productive than Fe²⁺-based metabolism, with S-based metabolism being considerably less productive. Internal recycling of sulphur within the surface ocean could conceivably raise rates of sulphur metabolism by a factor of 10 higher than the values predicted by our model.
　Although explicit climate calculations have not been performed here, our results are consistent with the idea that the Archean climate was warm, and possibly very hot. Some or most of our ecosystem scenarios are consistent with the carbon isotope record, depending on how that record is interpreted. If the conventional view is correct and organic carbon burial accounted for approximately 20％ of total carbon burial during the Archean, the only two of our phototroph-based model ecosystems are plausible. However, if a recent alternative analysis is correct and only approximately 0-10％ of total buried carbon was organic, then essentially all of our anaerobic ecosystems are plausible. A better understanding of both the geochemical and the biological records is needed to better constrain our models.』

Introduction
Nature of the Archean biosphere
　Limitations on primary productivity in the modern and Archean marine biosphere
　Anaerobic microbial ecosystems on the Archean Earth
　　H20- and CO-based metabolism
　　Sulphur-based metabolim
　　Iron-based metabolism
　Overview of model scenarios
Model description
　Ecosystem model
　Atmosphere model
　Coupled atmosphere-ecosystem model
Results
　Case 1: Methanogen-based ecosystem
　Case 2: Methanogen-acetogen ecosystem
　Case 3: Anoxygenic phototroph-acetogen ecosystem
　Case 4: Sulphur-based ecosystem
　Case 5: Iron-based ecosystem
Discussion
　H2 escape rates and implications for Archean climate
　Effects of solar UV radiation on ecosystem productivity
　Constraints imposed by the carbon isotope record
　Changes induced by the advent of oxygenic photosynthesis
Conclusions
Acknowledgements
References
Appendix 1 the atmospheric hydrogen budget
Appendix 2 Calculating dissolved H2 and CO using free energy constraints
Appendix 3 Abiotic uptake of atmospheric CO by the ocean