World’s oceans turning acidic faster than expected
Acidification caused by carbon emissions could bring some oceans to a tipping point.
(Page 2 of 2)
The challenge, Dr. McNeil says, is that this seasonal peak in acidification comes just as tiny swimming snails – which some call potato chips of the sea – exist as larvae. The tiny zooplankton, called pteropods, need carbonate to build their shells. They represent a vital source of food for many fish. Some pteropods already show signs of dissolving shells, the team reports.Skip to next paragraph
Subscribe Today to the Monitor
With a business-as-usual emissions scenario, McNeil and his colleague estimate that the Southern Ocean is likely to reach a wintertime tipping point for these creatures when atmospheric CO2 concentrations reach 450 parts per million, versus today’s level of around 383 ppm. That would occur by 2030 and no later than 2038, they estimate. The results appear in the Dec. 9 issue of the Proceedings of the National Academy of Sciences (PNAS).
On Tatoosh Island, off the northwest tip of Washington State’s Olympic Peninsula, researchers have found acidification trends running some 10 times faster than projected. The University of Chicago’s Timothy Wootton led a team that analyzed more than 24,500 water samples gathered over eight years. They found wide swings in carbonate levels during the year. As acidification increased, they found, larger shell-forming creatures such as mussels and barnacles lost ground to smaller ones and nonshell types of algae. The team’s work also appears in the same issue of PNAS.
As acidification changes the mix of marine life in coastal areas, it could eliminate species important to commercial fisheries, they say.
The picture is more complicated in the Caribbean. Researchers with the National Oceanic and Atmospheric Administration (NOAA) and the University of Miami tracked changes in acidification across the greater Caribbean between 1996 and 2006 using sensors placed on a cruise ship and satellite data.
The region shows a definite trend toward acidification through a reduction in dissolved carbonates, with the highest seasonal swings seen in the waters around the Florida Keys. The results appeared in the Oct. 31 issue of the Journal of Geophysical Research.
The implication for the Keys is unclear, says Dwight Gledhill, a reef expert with NOAA who led the team. Reefs there have clearly adapted to large seasonal swings in minerals.
“If you have a system that shows large variability throughout the year, that could mean that the system may be more resilient to future changes,” he says. “[Or] do they cross a critical threshold sooner?”