Carbon emissions sour ocean waters

It’s not just the spilled oil: Since the Industrial Revolution, Earth’s oceans have been soaking up unprecedented levels of atmospheric carbon dioxide as well as runoff from manufacturing processes. In a new review, Woods Hole Oceanographic Institution scientist Scott Doney describes the impact of human activities on the open ocean and coastal waters. Observations and models show that up to 30% of the carbon released by fossil-fuel combustion is absorbed by the ocean; with that rise in subsurface CO₂, a weak acid in seawater, the ocean’s pH plummets. Measurements of CO₂ and pH collected over the past two decades off Hawaiian shores show that the ocean is becoming more acidic—30 to 100 times faster than what geological records report. The shift in the ocean’s acid-base equilibrium due to excess CO₂ also hinders the precipitation of calcium carbonate, which makes up the shells and skeletons of many marine species. Yet another concern is hypoxia—dangerously low levels of subsurface oxygen caused by climate-warming-induced degradation of organic matter—which leads to anaerobic respiration conditions and produces even more CO₂. And yes, oil spills, even naturally occurring seeps from oil wells, release pernicious hydrocarbons into the marine environment. Most such industrial chemicals are “woefully undersampled,” writes Doney, whose summary calls on the oceanographic community to better coordinate its monitoring of the ocean’s biogeochemical cycle. (S. C. Doney, Science 328 , 1512, 2010 http://dx.doi.org/10.1126/science.1185198 .)