Scientists have discovered a much broader biodiversity in ocean plankton than previously thought, according to a set of new studies, published in the journal Science on Thursday. The latest analysis is said to be one of the most comprehensive ever conducted on plankton, tiny organisms that serve as the base of the marine food chain and provide half of the Earth’s oxygen.

The studies are based on findings of a multi-year voyage known as the “Tara Oceans project.” As part of the expedition, scientists collected 35,000 samples of plankton -- including viruses, bacteria, single-cell algae and fish larvae -- from 210 sites globally to determine the distribution of the organism, the Agence France-Presse (AFP) reported.

The scientists concluded that these organisms were far more complex than what they had imagined before.

“This is the largest DNA sequencing effort ever done for ocean science: analyses revealed around 40 million genes, the vast majority of which are new to science, thus hinting towards a much broader biodiversity of plankton than previously known,” Patrick Wincker, a researcher from the French National Sequencing Center, Genoscope, told AFP.

The research vessel, which sailed nearly 87,000 miles during the expedition, also helped scientists collect information about the oceans’ depth, temperature and salinity. Scientists also gathered information about how these tiny life forms interact with each other.

“When we mapped how planktonic organisms -- from viruses to small animal larvae -- interact with each other, we discovered that most of those interactions are parasitic, recycling nutrients back down the food chain,” Jeroen Raes from the Flanders Institute for Biotechnology and Free University of Brussels told AFP.

Scientists also identified more than 5,000 viral populations throughout the upper parts of the Earth’s oceans, while only 39 of those were similar to previously known viruses.

“The ocean is the largest ecosystem on Earth, and yet we know very little about it. This is particularly true for the plankton that inhabit the ocean,” scientists said in one of the studies.