Crocosphaera watsonii WH8501

Photo credits: Zehr, J. P., J. B. Waterbury, P. J. Turner, J. P. Montoya, E. Omoregie, G. F. Steward, A. Hansen, and D. M. Karl.
Crocosphaera watsonii (strain WH8501) belongs to a novel genus of marine unicellular (2.5-6 µm dia.) diazotrophic cyanobacteria that occur in ocean waters warmer than 24?C. It has been isolated from offshore open ocean oligotrophic waters in the western tropical Atlantic and from the tropical Pacific oceans where it may achieve cell densities exceeding 1,000 cells per milliliter within the euphotic zone. The size, abundance and rapid growth rate (i.e., 35 hour doubling time at 30?C) of Crocosphaera WH8501 indicate that this diazotrophic cyanobacterium is capable of contributing significantly to oceanic carbon and nitrogen budgets in the tropical regions of the world's oceans.