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In phytoplankton of the eastern tropical Pacific Ocean from 25 to 90 percent of the biomass (measured as chlorophyll a) and 20 to 80 percent of the inorganic carbon fixation were attributable to particles that could pass a screen with a 1-micrometer pore diameter. Evidence is presented that these are indeed autotrophic cells and not cell fragments.

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It has become of interest to study long‐term effects of CO2 concentration on plant growth, because intensive burning of fossil fuels and destruction of forests promise to continue the recent rise in atmospheric partial pressures of CO2 into the next century (Bolin, 1977; Stuiver, 1978). Effects of CO2 enrichment on growth of crop and forest species were therefore studied for the first time in the field in open top exposure chambers at daytime mean CO2 concentrations of 612, 936, 1292, and 1638 mg m−3, and in ambient control plots. Increased growth of plant parts of corn (Zea mays L. ‘Golden Bantam’), soybean [Glycine max L. (Merr.) ‘Ransom’], loblolly pine (Pinus taeda L.), and sweetgum (Liquidambar styraciflua L.) were recorded. Growth increases for soybean and sweetgum in elevated CO2 atmospheres were due to increases in leaf area and photosynthesis per unit leaf area, and decreases in conductance and, therefore, water use. For corn, however, photosynthesis was unaffected by CO2 enhancement, and growth stimulation appeared to be due to lowered conductance and increased water use efficiency alone.