Because they're large, diatoms are eaten by large zooplankton, which are then eaten by large fish, Hutchins explained.
The scientists found that greenhouse conditions favored smaller types of phytoplankton over diatoms. Such a shift would ripple up the food chain: as diatoms become scarce, animals that eat diatoms would become scarce, and so forth.
The food chain seems to be changing in a way that is not supporting these top predators, of which, of course, were the biggest, Hutchins said.
A shift away from diatoms towards smaller phytoplankton could also undermine a key climate regulator called the biological pump.
When diatoms die, their heavier carbon-based remains sink to the seafloor. This creates a pump whereby diatoms transport carbon from the atmosphere into deep-sea storage, where it remains for at least 1,000 years.
While smaller species often fix more carbon, they end up re-releasing CO2 in the surface ocean rather than storing it for long periods as the diatom-based community can do, Hutchins explained.
This scenario could make the ocean less able to soak up atmospheric carbon dioxide.
Right now, the ocean biology is sort of on our side, Hutchins said. About 50 percent of fossil fuel emissions since the industrial revolution is in the ocean, so if we didnt have the ocean, atmospheric CO2 would be roughly twice what it is now.
Hutchins and colleagues are doing related experiments in the north Atlantic Ocean and the Ross Sea, near Antarctica. The basic dynamics of a greenhouse ocean are not well understood, he noted.
Were trying to make a contribution by doing predictive experimental research that will help us understand where were headed, he said. Its unprecedented the rate at which things are shifting around.
The researchers collected the algae samples from the Bering Seas central basin and the sou
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| Contact: Terah DeJong tdejong@usc.edu 213-740-8606 University of Southern California Source:Eurekalert |