Basic chemistry teaches that dissolving carbon dioxide in seawater will increase acidity. With atmospheric CO2 levels rising—touching 400 parts per million for the first time in millennia this past May—it is therefore a safe bet that the world's oceans are becoming more acidic. But just how much more? And how much do those levels change from place to place—at the coast or out in open waters, or at the surface versus in the depths?
Those questions have few answers at present, mostly because acidity tests are difficult and expensive to conduct, and therefore infrequent and extremely limited in scope. A new prize aims to change that by offering a $1-million reward to inventors who can devise a cheaper and more accurate test of ocean acidity, which is measured in pH, a gauge of the concentration of ions in a solution. "We know nothing of pH at depth, which is a real concern," says biologist Paul Bunje, a senior director for oceans at the X PRIZE Foundation and the administrator of the new contest. "We have a spotty picture of what ocean acidification looks like around the world."
The new prize—dubbed the Wendy Schmidt Ocean Health X PRIZE in honor of its funder, who previously funded the successful oil spill cleanup prize that offered solutions to disasters like Exxon Valdez or BP's Macondo blowout in the Gulf—offers $1 million to the team that invents the most accurate sensors as well as another $1 million to the team that devises the most affordable and easy-to-use sensors. The sensor’s technical goals are threefold: to operate at depths of at least 3,000 meters, take measurements that are precise to the level of the annual pH change (roughly 0.002 on an acid-to-base scale that stretches from 0 to 14) and avoid the need for frequent recalibration. In addition, the sensors should be cheap so that they can be used widely: "pH sensing should not be limited to those scientists out on $40,000 per day research cruises," Bunje says. "These sensors need to be deployed globally, including in places like developing countries."
Present sensors rely on electrochemistry or dye-based tests (the most common of which is perhaps the litmus test), and can cost more than $5,000 per device. These sensors must also be sent back often to the manufacturer for recalibration to ensure accuracy. The free market offers little incentive for companies such as Honeywell to improve their pH sensors because the market—ocean researchers and the beverage industry—is relatively small and has conflicting needs; a sensor that may be perfectly adequate for cola carbonation may not work well in the deep Pacific. The goal of this X PRIZE, according to Bunje, is to turn ocean acidity readings into valuable and ubiquitous information as is the case with temperature data, and he hopes to inspire research spending well in excess of the prize money put up. For "every X PRIZE so far, the amount of money invested in winning that purse is 10 times the prize itself," Bunje notes. This prize may have a head start, thanks to the desire for cheap and accurate blood-pH monitors in medicine.
Researchers are excited by the idea of an inexpensive pH sensor. Marine biologist John Bruno of the University of North Carolina at Chapel Hill calls current ocean acidification data "trivial, because you can't buy cheap little devices to monitor [in place]." That's what is already done to measure temperature—logging local temps when attached to a rock underwater as often as every second—to register very local changes that can have big impacts. And ocean acidity levels vary even more than temperature in both location and time. "Having a cheap, simple device that you can purchase commercially—not build—would revolutionize the science of ocean acidification," Bruno adds.