This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Our oceans are becoming more acidic, which could have major consequences for marine life. Of particular concern is what this could mean for phytoplankton, the microscopic photosynthetic organisms that form the basis of marine food webs and produce roughly half of the oxygen on Earth.
Now, a study published in Nature Geoscience has found that the carbon dioxide we pump into the atmosphere is changing their internal chemistry. It was already known that rising carbon dioxide can boost plankton growth and low phosphate can limit it. But what was missing was an understanding of how these two stressors together change their nutrient use.
So a team led by the Yellow Sea Fisheries Research Institute and Harbin Institute of Technology in China grew a diatom species called Thalassiosira pseudonana in the laboratory. They exposed this common type of phytoplankton to high carbon dioxide and low phosphate to see how it would respond. They cultured the diatoms for 880 days, spanning more than 1,000 generations, and tested them in four different setups.
These were a control group mimicking current ocean conditions, an environment with low phosphate, an environment with high carbon dioxide and a combined environment with both high carbon dioxide and low phosphate. The team monitored the cells over the course of the experiment, profiling shifts in growth, gene expression and internal chemistry. To test whether any changes were inherited or just temporary stress reactions, they moved diatoms that had evolved under high carbon dioxide back to normal carbon dioxide levels after 1,000 generations.
They then looked beyond the laboratory by comparing their results against wild plankton samples and experiments with natural coastal plankton communities. The study authors also analyzed global gene-expression data and used Earth system models to forecast global changes through 2100. When carbon dioxide levels were high, diatoms grew faster and maintained higher rates of photosynthesis even when they were placed back under normal carbon dioxide levels.
This suggests the changes had become inherited rather than being temporary responses to their environment. Under low-phosphorus conditions, diatoms exposed to high carbon dioxide levels contained about 26% less organic phosphorus relative to carbon over time. This drop in phosphorus content reversed when carbon dioxide levels changed.
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