Figure 1.

Comparison of nitrogen fixation activity and the percentage of bright cells in Trichodesmium IMS101 cultures grown at different oxygen concentrations. A, Nitrogen fixation per volume of culture. The data are not normalized to the Chl concentration (C), as the stress-induced Chl bleaching in the high-oxygen culture would cause misleading values of the total nitrogen fixation under these conditions. B, Percentage of bright cells (defined as more than double the basic fluorescence yield of the average in the dark period). C, Chl concentration per volume of culture.