1. Environmental Biophysics and Molecular Ecology Program, Institute of Marine and Coastal Sciences, Rutgers University , New Brunswick, New Jersey 08901-8521, USA
2. Biology Department, College of William & Mary, Williamsburg, Virginia 23187, USA
3. Department of Molecular Biology and Biochemistry, Rutgers University, Piscataway, New Jersey 08854-8082, USA

Correspondence to: P. G. Falkowski¹ Correspondence and requests for materials should be addressed to P.F. (e-mail: Email: falko@imcs.rutgers.edu).

Abstract

The oxidation of the global ocean by cyanobacterial oxygenic photosynthesis, about 2,100 Myr ago¹, is presumed to have limited anoxygenic bacterial photosynthesis to oceanic regions that are both anoxic and illuminated^{2, 3}. The discovery of oxygen-requiring photosynthetic bacteria about 20 years ago⁴ changed this notion, indicating that anoxygenic bacterial photosynthesis could persist under oxidizing conditions. However, the distribution of aerobic photosynthetic bacteria in the world oceans, their photosynthetic competence and their relationship to oxygenic photoautotrophs on global scales are unknown. Here we report the first biophysical evidence demonstrating that aerobic bacterial photosynthesis is widespread in tropical surface waters of the eastern Pacific Ocean and in temperate coastal waters of the northwestern Atlantic. Our results indicate that these organisms account for 2–5% of the photosynthetic electron transport in the upper ocean.