Phytoplankton are mostly single-celled photosynthetic organisms that feed fish and marine mammals. They are responsible for nearly 50 percent of the earth's annual carbon-dioxide consumption and more than 45 percent of the oxygen production. Despite the important roles of modern phytoplankton, their evolutionary origins and rise to prominence in today's oceans was an unresolved question in marine science.

In the first study that looks at phytoplankton from combined perspectives of biology, chemistry and geology, researchers from three countries, including Texas A&M University at Galveston Assistant Professor Antonietta Quigg, who specializes in algae ecology and chemistry, examined modern phytoplankton development and reviewed their evolutionary history. Findings of the project appear in the July 16 issue of Science magazine.

Funding for the study is supported by a grant through the National Science Foundation Biocomplexity program, which aims to make new advances by bringing people together from different fields.

Despite the early origins of cyanobacteria, an essential component of modern phytoplankton, the ancestors of the majority of phytoplankton that dominate the modern seas did not appear until 250 million years ago, the researchers note. This is fairly recent in geological terms. Cyanobateria appeared 3.8 billion years ago. A cyanobacterium is a single-celled photosynthetic organism, which with the help of sunlight could make carbon dioxide and water into oxygen and energy providing chemicals.

The researchers showed that modern phytoplankton began to form at a time when the low oxygen conditions characterized much of the world's oceans. Since a cyanobacterium wa
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27-Jul-2004