A new study has suggested that the prolonged, extensive emission of greenhouse gases over the next few decades could have major impacts on ocean life.
UC Merced marine biologist Michael Beman's study has shown that the increased acidity will fundamentally alter the way nitrogen cycles throughout the sea.
"There is growing concern about this issue because human activities are modifying ocean pH so rapidly. While we do not know what the full effects of changing the nitrogen cycle will be, we performed experiments all over the world and believe that these changes will be global in extent," said Beman.
During the study, Beman and his coworkers decreased the pH level of ocean water - making it more acidic - in six total experiments at four different locations in the Atlantic and Pacific oceans: two near Hawaii, one off the coast of Los Angeles, one near Bermuda and two in the Sargasso Sea southeast of Bermuda.
In every instance, when the pH was decreased, the production of the oxidized forms of nitrogen used by phytoplankton and other microorganisms also decreased. That nitrogen is produced through the oxidation of ammonia in seawater by microscopic organisms.
The results showed that when the pH of the water was decreased from 8.1 to 8.0 - roughly the decrease expected over the next 20 to 30 years - ammonia oxidation rates decreased by an average of 21 percent over the six experiments, with a minimum decrease of 3 percent and a maximum of 44 percent.
Such a reduction could lead to a substantial shift in the chemical form of nitrogen supplied to phytoplankton, the single-celled aquatic "plants" that form the base of the ocean's food web. The decrease in nitrogen would likely favor smaller species of phytoplankton over larger ones, possibly creating a domino effect throughout the food web.
The study will be published in the journal Proceedings of the National Academy of Sciences (PNAS).