COURTESY DAVE KARL, TARA CLEMENTE & SAM WILSON Research crews aboard the vessel Kilo Moana deploy ocean pumping gear as part of an experiment aimed at triggering surface algal blooms to reduce atmospheric carbon.

Scientists ‘feed’ CO2 to algae

UH researchers hope the process will help phytoplankton grow

"Hungry Oceans," part of a new series titled "Discovery Project Earth," will show the oceanographers mimicking nature by pumping cold, nutrient-rich water from the deep ocean to low-nutrient surface waters to induce algal blooms to consume carbon dioxide.

The audience will go to sea on the University of Hawaii vessel Kilo Moana for the documentary, shown on Oceanic Channel 69 and Oceanic Digital Channel 333.

UH oceanographer David Karl, director of the Hawaii-based Center for Microbial Oceanography: Research and Education, and UH-Manoa chief scientist Eric Grabowski were lead investigators with Oregon State University professor Ricardo Letelier, a former UH graduate student and co-investigator in the microbial center.

Karl said he and Letelier will participate in the channel's blog site, answering questions about the show, and they will set up other outreach activities related to the "Discovery Project Earth" series.

Karl said the Ocean Productivity Perturbation Experiment, called OPPEX-1, was designed to test a theory he and Letelier have that lifting nutrient-rich deep ocean water to surface waters deficient in nitrogen and phosphorous could stimulate phytoplankton production.

Microorganisms then would suck up atmospheric carbon dioxide and sink to the ocean bottom, according to their theory, just published in the journal Marine Ecology Progress Series.

Commercial wave-driven ocean upwelling pumps were used for the project at Station Aloha, about 60 miles north of Oahu. Water was pumped to the surface using the up-and-down motion of the waves.

Nature fought back during the first test.

"The ocean destroyed our pump in one day," Angelicque "Angel" White, an OSU postdoctoral researcher, said in a EurekAlert report on the project.

"Initially the system worked, and we were able to bring cold water to the surface and control the depth of its release. Now we need to work on the engineering aspect," she said.

The goal is to understand how marine microbial ecosystems respond to large-scale disturbances, the scientists said, explaining seemingly barren regions comprise more than two-thirds of oceans and nearly 40 percent of the earth.

"It is a large area of exchange between the atmosphere and the ocean, and understanding large-scale interactions is critical to understanding climate change," Letelier said.

It was proposed in 1976 that scientists could use wave energy to pump water from the deep ocean to the surface and fuel plankton growth, he said.

"But there are many nuances," Letelier pointed out. "Simply bringing nutrients to the surface can result in the wrong kinds of biological growth. It can also bring water enriched with carbon dioxide, which can de-gas into the atmosphere.

"If you're adding more CO2 than subtracting by fertilizing the ocean, you're running the wheel in the wrong direction."

At Station Aloha, where UH scientists have run Hawaii Ocean Time-series studies since 1988, water at the 15,000-foot depth has too much carbon dioxide because of sunken decaying organisms, the scientists said. But water at higher levels - 990 to 2,310 feet - has the right levels of nitrogen and phosphorus to trigger blooms, they said.

The researchers used undersea gliders to monitor water from the pump to determine how far and how fast it dispersed and how much impact it would have at the surface.

Karl said OPPEX-2 is in the planning stages for a second test of the Karl-Letelier hypothesis. Meanwhile, the researchers are excited about their experiment appearing on the Discovery Channel, he said.

"We hope that this will promote science and engineering among the next generation and educate the public at large," Karl said.