Acidic Oceans

Scripps to employ new tool to assess potential for ecosystem damage

Scripps Institution of Oceanography at UC San Diego marine chemist Andrew Dickson plans to purchase and deploy an autonomous buoy-mounted sensor to study the effect increasingly acidic ocean water could be having on ecosystems in the California Current.

Dickson is collaborating with Montana-based developers of the sensor, who received a $980,000 federal grant in June to further its development. Recently published findings by other researchers have indicated a disturbing upwelling of acidic waters into coastal regions that support sea urchins, abalone and other marine invertebrates whose ability to form shells could be impaired by the corrosive water. Dickson said recent discoveries like that underscore the need for more detailed measurements.

"If the instrument works as we hope, it will be a valuable tool that will enable us to characterize the extent and intensity of incursions of these high-CO₂ waters onto the California shelf and better understand the stresses ecosystems are under," said Dickson.

The device, known as a Submersible Autonomous Moored Instrument, is mounted onto buoys and suspended at a depth of up to several hundred meters, where it measures pH for long periods of time. The Missoula, Montana firm Sunburst Sensors and University of Montana researcher Mike DeGrandpre developed the instrument, with input from other researchers including Dickson, who helped them run tests on the instrument at Scripps and who is working with them to improve the instrument.

"By observing pH over long time periods, ocean scientists will be able to determine the processes that control seawater pH, its natural range of variability, and how pH is changing as CO₂ is absorbed by the oceans," DeGrandpre said.

Dickson said he plans to deploy his new instrument for initial testing in Southern California waters within the next six months and then hopes to install it on a research buoy near the California/Oregon border in a proposed collaboration headed by Cal State University San Marcos researcher Victoria Fabry.

In May, NOAA Pacific Marine Environmental Laboratory researcher Richard Feely reported in the journal Science that upwelling ocean water along the California coast is already contaminated with anthropogenic CO₂ in addition to the CO2 that accumulates in such subsurface waters from normal biological activity. The resulting enhanced acidity could be problematic, but there is still much to be understood, said Dickson.

"What's the intensity and frequency of these events? Is it a few days now and then or do acidic conditions persist over a protracted period of time?" said Dickson. "We fear that these intermittent acidic conditions could pose severe problems for organisms and their associated ecosystems, but — as yet — we just don't know."

—Robert Monroe

July/Augst 2008