Massive bloom or surface aggregation of Trichodesmium near New Caledonia in the tropical Pacific Ocean, as viewed by a satellite from space (long brownish streaks are the bloom; white objects are clouds)NASAA key phytoplankton can adapt metabolically to long-term high carbon dioxide (CO2) levels, and those adaptive changes can become permanent, according to a study published today (September 1) in Nature Communications. Researchers at the University of Southern California (USC) and the Woods Hole Oceanographic Institute in Massachusetts grew Trichodesmium erythraeum, a cyanobacterium common in oceans, in carbon dioxide levels that mimicked the projected atmospheric levels in 2100—approximately double the current levels—for four-and-a-half years. The cyanobacteria responded with increased growth and higher nitrogen fixation rates. When returned to lower CO2 levels, the T. erythraeum did not decrease their growth or nitrogen fixation rates.
“They couldn’t come back to the lower current rate. They were stuck in the fast lane,” said study coauthor David Hutchins of USC. “It’s very surprising, but it’s also a little ominous that a key microbe in the ocean’s nutrient cycle could be irreversibly changed by the acidification of the ocean.”
T. erythraeum is widely distributed in the world’s oceans and is important to the marine food web because it fixes nitrogen, making the element available to other organisms in the ocean. Previous studies had demonstrated that phytoplankton respond to high CO2 levels with high growth and nitrogen fixation, but those studies were relatively short-term, lasting a few weeks.
Hutchins and his colleagues used experimental evolution to study the cyanobacterium under a variety of environmental ...
