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CO2 emissions could doom fishing industry

CO2 emissions could doom fishing industry

CO2 emissions could doom fishing industry
July 3, 2008

Aside from warming climate, rising carbon dioxide emissions are contributing to ocean acidification, threatening sea live, warn researchers writing in the journal Science. This trend makes it all the more important to reduce emissions, argue the authors.

The oceans have absorbed about 40% of the anthropogenic carbon dioxide emissions over the past two centuries. While this has slowed global warming, the extra carbon dioxide has caused the ocean’s average surface pH become about 0.1 units more acidic compared to pre-industrial levels. Continuing emissions could cause the ocean’s pH to drop by as much as 0.35 units by the 2050.

Ocean acidification is important because it reduces the availability of carbonate ions necessary for the formation of shells and exoskeletons by marine organisms. Corals, marine plankton, and shellfish would be especially affected, although some research has suggested that even juvenile fish would suffer from higher-than-normal CO2 levels.

Surface ocean pH decline. The white contour lines illustrate the expected maximum pH decrease of average surface ocean waters in the future (in pH units) as a function of total anthropogenic CO2 emissions (in petagrams of carbon, 1 Pg = 1015 g) and release time (in years, see supporting online material). For example, if humans release a total of 1200 Pg C over 1000 years, surface ocean pH will drop by about 0.2 units arrow). Image and caption courtesy of Science.

“We know that ocean acidification will damage corals and other organisms, but there’s just no experimental data on how most species might be affected,” said co-author Ken Caldeira of the Carnegie Institution’s Department of Global Ecology at Stanford University. “Most experiments have been done in the lab with just a few individuals. While the results are alarming, it’s nearly impossible to predict how this unprecedented acidification will affect entire ecosystems.”

Some researchers have cautioned that the ecological changes wrought by increasingly acidic conditions may have significant economic consequences, especially for marine fisheries. Many commercial fish species rely on plankton and other carbonate-dependent organisms for sustenance.

Because ocean acidification is largely independent of temperature, strategies to address climate change independent of reining in emissions (such as geoengineering) will not solve the problem.

“We need to consider ocean chemistry effects, and not just the climate effects, of CO2 emissions. That means we need to work much harder to decrease CO2 emissions,” says Caldeira. “While a doubling of atmospheric CO2 may seem a realistic target for climate goals, such a level may mean the end of coral reefs and other valuable marine resources.”

R.E. Zeebe, J.C. Zachos, K. Caldeira, and T. Tyrrell (2008). Carbon Emissions and Acidification. 4 JULY 2008 VOL 321 SCIENCE

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