The Moderate Resolution Imaging Spectroradiometer (MODIS) flying aboard NASA's Aqua satellite acquired this true-color image of a large phytoplankton bloom in the Norwegian Sea, off of Iceland, on July 6, 2013. Researchers say changing ocean acidity levels, influenced by the seas' uptake of CO2, could dramatically affect plankton communities. File photo by UPI/J.Schmaltz/NASA |
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BOSTON, July 22 (UPI) -- Mollusks aren't the only ones in trouble as the ocean takes up more carbon dioxide and further acidifies. Ocean acidification will also dramatically affect phytoplankton populations all over the world -- diminishing some species, while sustaining others.
In a new study, published in the journal Nature Climate Change, researchers at MIT used global warming models to project increases in ocean acidification. To date, the ocean has absorbed 30 percent of manmade CO2 released into the atmosphere.
After running their models, researchers compared their projections with a number of studies that looked at how marine microorganisms fare at various pH levels. Scientists analyzed the findings of 49 papers, encompassing 154 phytoplankton experiments.
To organize their work, researchers divided the phytoplankton into six functional categories, including diatoms, Prochlorococcus and coccolithophores. But even within these groups, researchers found "winners" and "losers" as the ocean acidifies.
"The fact that there are so many different possible changes, that different phytoplankton respond differently, means there might be some quite traumatic changes in the communities over the course of the 21st century," Stephanie Dutkiewicz, a principal research scientist in MIT's Center for Global Change Science, explained in a press release. "A whole rearrangement of the communities means something to both the food web further up, but also for things like cycling of carbon."
Scientists say even a slight advantage in more acidic waters could allow some species to outcompete and wipe out entire other species, disrupting the current balance of phytoplankton.
"Normally, over evolutionary time, things come to a stable point where multiple species can live together," Dutkiewicz said. "But if one of them gets a boost, even though the other might get a boost, but not as big, it might get outcompeted. So you might get whole species just disappearing because responses are slightly different."
Just as small changes in pH levels could turn into big chances in the phytoplankton community, changes among the small creatures at the bottom of the food chain could ultimately have significant effects on the big species at the top.
"Generally, a polar bear eats things that start feeding on a diatom, and is probably not fed by something that feeds on Prochlorococcus, for example," Dutkiewicz said. "The whole food chain is going to be different."
But researchers say they need to better understand the competition among different types of phytoplankton before they can make accurate predictions about the effects of ocean acidification on ocean food chains.
Their research, Dutkiewicz says, offers a broad brush stroke. Further experimentation will reveal finer details.
