A Two-Million-Dollar Race To Track The Changing Oceans

May the best chemistry nerds win

Aboard the R/V Kilo Moana, the tension is palpable.

Five teams stare nervously at the water’s surface while the rosette climbs ever so slowly back up from the deep. This piece of oceanographic equipment is loaded down with tall grey bottles of water samples and five experimental pH meters strapped tightly to its frame. Quite literally millions of dollars are at stake, and the teams, who’ve been working for a year on their entries in the Wendy Schmidt Ocean XPrize, are anxious to see whether they’ve survived the trip down 10,000 feet into the deep, dark ocean.

Ocean acidification—global warming’s lesser-known cousin—is one of the biggest threats facing marine environments due to climate change. When carbon dioxide is dissolved in seawater, the water becomes more acidic, stressing and even killing important species like corals. The second Ocean XPrize seeks to draw attention to this formidable problem, and incentivize technologies that will help scientists document and understand the changing chemistry of our oceans: $2 million dollars for the most accurate, efficient, and user-friendly pH meter the ocean has ever seen.

It’s easy to measure pH in the lab, where a bench-top electrode can be easily calibrated and stored in ideal conditions to prevent damage. But the salty ocean is unpredictable, corrosive, and full of organisms that encrust and eat away at anything that comes onto their turf. Plus, the oceans are deep—a good device must both be useful on the surface and still provide data if strapped to a submersible as it explores the darkest depths. Scientists need a pH meter that is as rugged as it is accurate and affordable.

The $2 million prize is split into two purses. For the $1 million performance purse, accuracy, precision, and stability are the most important qualities; the other half of the prize money will go to the team that scores best on affordability and ease of use. “If there is one device that can do it all, it’ll clean up,” said Paul Bunje, senior director of the Wendy Schmidt Ocean XPrize. “If you’re able to do it all, you can win all $2 million.”

This Monday, the winners will be announced at the Wendy Schmidt Ocean XPrize awards gala in New York City. The event will also feature a panel discussion on the future of ocean health, with distinguished panelists including Richard Spinrad, a chief scientist with the National Oceanic and Atmospheric Administration, and Sherri Goodman, the CEO of Ocean Leadership. Until then, the teams are keeping their fingers crossed.

Eye on the Prize

Seventy-seven teams initially set their sights on the prize, though only twenty-six were able to get their prototypes ready in time. Last September, eighteen of those made it past the initial round and underwent the first real test of the competition at the Monterrey Bay Aquarium Research Institute: accuracy and stability. “We had a very, very precise lab setup,” explains Jyotika Virmani, director of technical operations. Virmani oversaw the arrangements for the facilities where the each round of the competition occurred as well as the scientific validation team. After two months in lab conditions, fourteen teams moved on to Seattle where they were tested in ever-changing coastal conditions. In addition to performance, each team was judged on their affordability and ease of use. “Because what we want to do is have sensors that people can use,” Virmani reiterates. “So you can get it out to managers and even to the public, to schools.”

The five finalist sensors were put to their last test aboard the R/V Kilo Moana, a research vessel owned by the U.S. Navy and run by the University of Hawaii Marine Center. The teams spent a week on board at Station ALOHA, a well-studied 110 square miles of ocean about 100 miles north of Oahu. The sensors were rigorously tested in open-ocean conditions, including for their ability to create a complete pH profile from 0 to 3,000 meters deep.

What it Takes to Win

The judges are comparing the five sensors’ results to reference data for criteria like accuracy—data which, as Bunje notes, was no small feat to generate. XPrize pulled together some of the best pH scientists in the world, led by Richard Feeley, senior scientist at the National Oceanic and Atmospheric Administration Pacific Marine Environmental Laboratory in Seattle. “We had to bring the lab with us,” says Bunje, “a 20-foot shipping container with a laboratory and hundreds of thousands of dollars worth of equipment in it.”


Some of the sensors use technology very similar to that used by Feeley’s validation team, but others are entirely different. “I wasn’t sure how many different technologies we would see,” says Chris Kellogg, one of the prize’s judges. She was impressed with the diversity, not only of approaches, but of the teams themselves. “There was a team of high school students from California,” she says. “The learning curve of how quickly they went from not having a clue what ocean pH is, much less how to measure it, to building a sensor and having it work and pull in some really fantastic data has been wild.”

Though the teenagers didn’t make it into the final phase, the five final teams represent five completely different technological approaches to measuring pH. They hail from Norway, Japan, the United Kingdom, and the United States. And they’ve invested an impressive amount in the effort, both time and money. “When you start to add up what all of these teams have invested in producing their innovations, what we have found on every XPrize is that there’s a tenfold investment by teams. So 10 times those teams have put in what the prize purse is worth.”

The winners will be announced on July 20th, but even then, the competition isn’t really over, Bunje says. “One of our little catchphrases at XPrize is that the real change happens, the real prize starts the day the purse is won, because that’s when they all go out and start literally changing the world.”


Team Xylem

  • Country of Origin: Norway / U.S.A.
  • Team Leader: Jostein Hovdenes
  • Technological approach: optics

With decades of experience in designing and manufacturing aquatic sensors, it’s not entirely surprising that Xylem made it to this final round—or, at least, that’s the impression you get from team leader Jostein Hovdenes, a man of few words and a soft-spoken confidence that would make you think the team has the competition in the bag. “We have sensors for oxygen, conductivity, salinity, things like that,” he explains. “So [pH] was actually the next logical step.”

Xylem created an optical pH electrode to tackle the tough demands of this Ocean XPrize competition. Their new sensor fits in their already-popular Seaguard sensor housing, so that it can be employed alongside the other oceanographic instruments the company currently sells.

Xylem’s sensor relies upon a fluorescent dye that changes color depending upon the pH of the surrounding water. LEDs shine blue light on a thin film containing this dye, and the sensor reads which colors are emitted to determine pH. There are no moving parts, and the system as a whole consumes very little power, making it ideal for long deployments with limited battery life. And as a bonus, the casing has already been rated to 6,000 meters, so the team isn’t too worried that they’ll have issues at depth.

But while the casing has been tested, the pH sensor itself is relatively new, and Hovdenes thinks they “could have done better.” Though he was vague on the specifics, Hovdenes mentioned that the competition has revealed “traps related to our technology” and he was “not too optimistic” about the team’s odds of winning.

When I ask Hovdenes what he and his teammates would do if they did win, though, he is charmingly concise: “We hope to change the way the pH is measured in the ocean.”

Sunburst Sensors

  • Country of Origin: U.S.A.
  • Team Leader: James Beck
  • Technological approach: spectrophotometry

Spectrophotometry—the measurement of intensity of known wavelengths of light after they pass through a substance—is the ‘gold standard’ when it comes to detecting pH. So, in some ways, Sunburst Sensors took a classical approach to creating a pH sensor by using the same overall technology that has been commonplace for decades. “The method is simple. So that’s a strong point,” says James Beck, team leader and CEO of Sunburst Sensors.

Sunburst’s sensor, the T-SAMI (Titanium Submersible Autonomous Moored Instrument-pH—“We’re not terribly clever in naming,” Beck notes), consists of a small area where water is drawn in from the surrounding ocean and mixed with dyes whose colors are pH-dependent. The sensor then shines a light through the now-colored water and measures how much is absorbed, thus telling the instrument what color—and thus pH—the water is.

It’s nearly identical to the method used by the XPrize analytical team to create the reference values the judges will compare the teams against. “They’re basically doing this on the bench top; we’re doing it with a device,” Beck says.

One large strike against the T-SAMI, though, is that it’s slow—it can’t take quick, continuous measurements, and thus has the deck stacked against it when it comes to creating a complete depth profile of pH. “The water temperature goes from room temp down to almost freezing in less than an hour, and the pH and pressure are changing fast, too,” he explains. It’s possible that the T-SAMI simply won’t be able to keep up with the speedier sensors.

There’s also the price: Sunburst’s usual SAMI model runs upwards of $17,000, and this one is made of titanium, a more expensive metal casing.

But what Beck is most worried about it how all the moving parts will fare as they dive down to 3,000 meters. The company is based in the landlocked state of Montana, and thus has never been able to test their sensors in the deep, open ocean. “We just don’t have any way of simulating that,” he says.

Beck is optimistic about their chances, but was even more enthused by the opportunity the competition provided. “If we win, that’s great, but at the end of the day hopefully we’ll be a lot smarter about what we’re doing.”


  • Country of Origin: Japan
  • Team Leader: Yoshiyuki Nakano
  • Technological approach: hybrid (glass electrode + spectrophotometry)

The team name says it all: HpHS, which stands for Hybrid pH Sensor, is the only sensor to use two sensing technologies. It combines two tried and true methods for determining pH in one sleek model, thus getting the best of both worlds.

Like Sunburst Sensors’ model, the HpHS sensor has a spectrophotometric pH detector that uses color-changing dyes to determine pH. But since this method is slow and involves a lot of moving parts and reagents, the team coupled it to a separate electrode. Technology akin to the electrode half of HpHS is a very commonly used method of measuring pH. These electrodes contain liquids that react to the presence of hydrogen ions in water, creating a change in voltage. That voltage can be read in comparison to a reference electrode (which does not react to the same ions), and the pH calculated using an equation that relates the difference in the current to ion concentration.

While each of these methods on their own have drawbacks, the combination helps avoid some of their negatives. As team leader Yoshiyuki Nakano explains, the “spectrophotometric system is very accurate but uses more energy,” while the electrode “is not so accurate but has less power consumption.”

The big bonus of having two sensor types: the sensor is self-calibrating, and thus can adjust to environmental fluctuations on the fly. The electrode can generate quick measurements but is prone to drifting away from its calibrated settings, and thus needs to be re-checked often. In the HpHS model, the spectrophotometric half does that calibration for the electrode, thus preventing that problem.

It’s the only hybrid sensor in the world, Nakano says confidently. They think they’ve got a good chance at winning, but won’t go so far as to say they will. “We are looking forward to seeing the results and the possibilities post-prize.”

Team Durafet

  • Country of Origin: U.S.A.
  • Team Leader: Bob Carlson
  • Technological approach: potentiometry (ion-sensitive field-effect transistor electrode)

The members of Team Durafet are far from newbies in the area of pH sensing. They have spent five years and over five million dollars designing, building, calibrating, and testing the prototype for the Deep-Sea Durafet pH sensor. Their complete model has been down to 2,000 meters—the deepest of any of the finalists—and was able to handle warm tropic seas and the icy waters of Antarctica with equal ease in field tests. “We’ve been building these things for a couple of years now so we worked out the first bugs already,” said Yui Takeshita, the team’s representative on the cruise.

The electrodes used in the Deep-Sea Durafet are similar to the electrode in the HpHS sensor, but instead of using glass, the electrode uses a special kind of material which directly responds to hydrogen ions. Both this ‘ion-sensitive’ electrode and a reference electrode (which isn’t sensitive to hydrogen ions) are exposed to the water at the same time while in a circuit, and from the resulting current, the pH of the water can be calculated.

Most electrodes are too fragile for open ocean purposes, though, Takeshita explains. So Durafet had to work with Honeywell, a commercial electrode producer, for years to create the current Durafet-3 electrodes used in the Deep-Sea Durafet.

The downside of using electrodes is that they need to be well calibrated—everything relies on the reference electrode and the circuitry, so if seawater leaks in anywhere it shouldn’t be, it will all go bust. And while Takeshita is confident that the model will be fine down to 2,000 meters, that’s still 1,000 meters short of the challenge’s requirements. The Deep-Sea Durafet is also extremely pricey.

Still, Team Durafet’s well-tested model is the one to beat, and Takeshita knows it: “I’m feeling good about my odds.”

ANB Sensors

  • Country of Origin: U.K.
  • Team Leader: Nathan Lawrence
  • Technological approach: electrochemistry

Some might see ANB Sensors as the underdogs in the competition—they did, after all, only begin to make their prototype a month before they had to have it in hand for the first lab trials. “It wasn’t working at three o’clock in the morning just before the start of Phase 2A,” Lawrence says, laughing. “but eventually, we got it working.”

Their ‘pHenom’ sensor uses patented solid-state electrodes that do not contain any vacuum or gas compartments. The pHenom contains multiple electrodes, each with its own unique chemistry able to react to the concentration of certain ions in the water and output a voltage in response. “The magic of the sensor is the chemistry of the electrode, which provides for changes in voltage across the electrodes depending upon pH,” the team explains. “Otherwise—and keep this quiet—the system is very simple.”

Solid-state electrodes provide ANB with one huge advantage: no calibration required. The pHenom can be dropped into any water anywhere and be good to go.

There are several other qualities that make their model stand out, too. At a glance, it just looks different: its flattened, white, 3D-printed casing stands in stark contrast with the cylindrical, metal sensors of the other four teams. It’s also the only sensor with a clear answer to one of the most frustrating problems with oceanographic instruments: biofouling. Anything that gets put in the ocean becomes habitat for a diversity of critters from barnacles to sponges that can damage instruments and are costly to remove. The pHenom is built from a special plastic that resists the attachment of marine organisms. But most importantly, it’s by far the cheapest to make. The team estimated that it would cost was about $1,000—a tenth or less of the price of other models in the finals. The price, low-maintenance housing, and ease of use make it a strong contender for the affordability purse.

However, the team is quick to note that while their tech is cheap and user-friendly, it’s also untested. “Depth and pressure are the biggest concerns,” Lawrence says. In this final round, their sensor is being judged on how well it performed all the way down about 10,000 feet and back up—and prior to the competition, the deepest a team had taken any of their pH sensors was 10 feet.

When I asked Lawrence and his team member William Barrow if they thought they were going to win, they were quite confident. “No,” Barrow replied firmly as the two laughed. Lawrence shook his head. “Not a chance.”