The ocean is changing colors, researchers say. Here's what it means.

The researchers analyzed satellite data on the open ocean collected from 2003 to 2022 by a NASA instrument that combs through the planet every two days to measure light wavelength, according to the paper.

The presence of chlorophyll in open ocean is a proxy for concentrations of phytoplankton biomass. The colors indicate how chlorophyll concentration is changing at specific latitudes, in which the subtropics are generally losing chlorophyll, and the polar regions -- the high-latitude regions -- are greening, the researchers said.

Green areas became greener, especially in the northern hemisphere, and blue regions "got even bluer," according to a press release by Duke University.

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How Earth's Atmosphere Changed

A DENSE RAINFOREST or other verdant terrestrial vegetation may be what first comes to mind at the mention of photosynthesis. Yet the clouds of phytoplankton that fill the oceans are the major drivers of that process in nature. 

The plantlike single-celled aquatic microbes generate more than 50 percent of the oxygen in the atmosphere, and they absorb nearly half of the carbon dioxide, converting it into the glucose, fats, proteins and other organic molecules that nourish the food web of the oceans.

A recently published study in Current Biology finally pins down the source of this unparalleled photosynthetic efficiency, which has long baffled scientists. The new research found that some phytoplankton are equipped with an extra internal membrane that carries a “proton pump” enzyme that supercharges their ability to convert carbon dioxide into other substances. 

The enhancements due to this one protein modification seem to contribute to the production of nearly 12 percent of the oxygen in the air and as much as 25 percent of all the carbon “fixed” (locked into organic compounds) in the ocean.

Surprisingly, that photosynthetic innovation seems to have evolved by chance from a membrane protein that was originally used for digestion in the ancestor of the phytoplankton. 

In addition to explaining the cells’ prowess at photosynthesis, the new work helps to confirm the theory that those phytoplankton arose through a symbiotic alliance between a protozoan and a resilient red alga.

“I find it staggering that a proton enzyme that we have known for so many decades is responsible for maintaining such a crucial phenomenon on Earth,” said Dennis Brown, a cell biologist at Harvard Medical School who studies the functions of membrane proteins and was not involved in the study.

Researchers knew that certain classes of phytoplankton—diatoms, dinoflagellates, and coccolithophores—stand out for their exceptional photosynthetic abilities. 

Those cells are extremely proficient at absorbing carbon dioxide from their environment and directing it to their chloroplasts for photosynthesis, but the details of why they are so good at it haven’t been very clear. A feature unique to those three groups of phytoplankton, however, is that they have an extra membrane around their chloroplasts.  READ MORE...