High nutrient levels could make coastal waters more susceptible to ocean acidification, suggests a study published online this week in Nature Geoscience. Alongside atmospheric inputs of carbon dioxide, human inputs of nutrients to the coastal ocean can lead to an increase in the acidity of these waters.
Wei-Jun Cai and colleagues use data collected in the northern Gulf of Mexico and the East China Sea to examine the influence of nutrient inputs on the acidity of coastal waters. As expected, high levels of nutrients led to phytoplankton blooms and an increase in seawater acidity, owing to a rise in microbial activity. But model simulations suggest that the rise in acidity exceeded that expected from simply adding the separate effects of phytoplankton blooms and atmospheric inputs of carbon dioxide.
The researchers suggest that the additional increase in acidity results from a reduction in the ability of these waters to buffer changes in pH.