Why we see red when looking at ocean plants

Rutgers marine scientists say phytoplankton changed color 250 million years ago

Green was the dominant color for plants both on land and in the ocean until about 250 million years ago when changes in the ocean’s oxygen content – possibly sparked by a cataclysmic event – helped bring basic ocean plants with a red color to prominence – a status they retain today. That’s the view of a group led by marine scientists from Rutgers, The State University of New Jersey, in a paper, “The Evolutionary Inheritance of Elemental Stoichiometry in Marine Phytoplankton” in the journal Nature, published Thursday (Sept. 18).

Studying ancient fossils plus current species of microscopic ocean plants called phytoplankton, the scientists found evidence that a “phytoplankton schism” took place after a global ocean oxygen depletion killed 85 percent of the organisms living in the ocean about 250 million years ago at the end of the Permian era. “This paved the way for the evolution of red phytoplankton,” said one of the paper’s authors, Paul G. Falkowski, professor in the Environmental Biophysics and Molecular Ecology Program at Rutgers’ Institute of Marine and Coastal Sciences (IMCS). Falkowski has a joint appointment with Rutgers’ Department of Geological Sciences.

The Permian era, prior to the advent of the dinosaurs, ended in a global extinction scientists believe may have been linked to extraterrestrial collisions or earthly eruptions or explosions.

“Plants on land are green, and they inherited the cell components that gave them a green color about 400 million years ago,” Falkowski said. “But most of plants or phytoplankton in the ocean are red – they inherited their pigments about 250 million years ago. Our paper suggests that a global ocean oxygen depletion changed the chemistry of the ocean and selected for red phytoplankton. The ocean has been dominated by the red line ever since.”

The research is supported under the National Science Foundation’s Biocomplexity Program. Lead author on the paper is Antonietta Quigg, formerly of IMCS and now at Texas A&M University. Besides Falkowski, co-authors include Zoe V. Finkel and Andrew J. Irwin of IMCS, Yair Rosenthal of IMCS and the Department of Geological Sciences, Oscar Schofield of IMCS and Rutgers’ Coastal Ocean Observation Laboratory and John R. Reinfelder of Rutgers’ Department of Environmental Sciences. Co-authors from Princeton University Department of Geosciences are Tung-Yuan Ho and Francois M.M. Morel.