From the text ... 'These data demonstrate that the blue-green algae are possible one of the microbial groups most adversely affected in ecosystems exposed to SO2 and NOx pollution. The potential sensitivity of bule-green agaae are particularly interesting because the blue-green agae are the dominant N2-fixing organisms in some ecosystems. These organisms may be particularly important in providing nitrogen for rice production in tropical regions, and many of these rice growing sites are sufficiently close to sources of anthropogenic SO2 to warrant concern. We have also observed that photosynthesis of blue-green gassing for 24 hrs. with 1 ppm SO2 in air, a level that has been reprorted in Chicago. Full details of these experiments will be published elsewhere.'