Alexandra (Alex) Z. Worden (born 1970) is a microbial ecologist and genome scientist known for her expertise in the ecology and evolution of ocean microbes and their influence on global biogeochemical cycles.

in history and performed a concentration in Earth, Atmospheric and Planetary Sciences coursework at the Massachusetts Institute of Technology and worked in the laboratories of the marine geochemist and paleoceanographer John M. Edmond,[1] the climate scientist Reginald Newell,[2] and the biological oceanographer Sallie W. Chisholm.

In 2007 she was recruited to the Monterey Bay Aquarium Research Institute on the U.S. West Coast while it was under the leadership of Marcia McNutt, who now serves as president of the US National Academy of Sciences.

She was selected from an international pool of leading scientists as a Gordon and Betty Moore Foundation Marine Investigator in 2013,[9] an award given for her "creativity, innovation, and potential to make major, new breakthroughs".

[18][19] She initiated this research through an NSF Postdoctoral Fellowship in Microbial Biology and expanded it thereafter by adapting multiple molecular and omic methods to characterize the evolution and ecological contributions of these photosynthetic plankton, which are now known to be major ocean primary producers.

[20][21] At Scripps Institution of Oceanography, a different research pursuit on microbial interactions, while in the laboratory of Farooq Azam, led to her work that overturned the idea that Vibrio cholerae existed primarily attached to copepods in aquatic systems.

[23] The concept was embraced by the scientific community in several later perspectives,[24][25] and is being pursued by human microbiome-biologist Jeroen Raes and microbial oceanographer Edward DeLong.