WASHINGTON, Sha'ban 3, 1436, May 21, 2015, SPA -- Scientists on Thursday unveiled the most comprehensive analysis ever undertaken of the world's ocean plankton, the tiny organisms that serve as food for marine creatures such as the blue whale, but also provide half the oxygen we breathe, Reuters reported. The researchers spent 3-1/2 years aboard the schooner Tara, taking 35,000 samples of plankton from 210 sites globally, determining the distribution of the organisms, tracking how they interact with one another and carrying out genetic analyses. Plankton include microscopic plants and animals, fish larvae, bacteria, viruses and other microorganisms that drift in the oceans. -- SPA 23:44 LOCAL TIME 20:44 GMT www.spa.gov.sa/w