We report that the algal pavement just behind the reef crest at Enewetak Atoll produces nitrate at measurable rates. In situ and in vitro incubations with N-Serve® indicate that the autotrophic pathway involving two separate organisms is effective in this oxidation of ammonia to nitrate. Significant nitrification is indicated throughout the reef environment; Nitrobacter agilis has specifically been identified as at least one of the organisms responsible for the terminal oxidation of nitrite to nitrate.