Seawater near Japan growing acidic / 23 years of data show CO2-influenced drop in pH level; effect on sea life unclear

Waters near Japan are becoming less alkaline, and the change is so sudden that if the pace of acidification keeps up, it could threaten the ecosystem in 100 years, according to researchers studying the phenomenon.

Ocean water is mildly alkaline by nature, but when the amount of carbon dioxide in seawater increases, the water becomes less alkaline. On the pH scale, ocean water is usually about 8.1, which is alkaline. Depending on location, however, seawater alkalinity is getting closer to the neutral figure of 7.

The drop in alkaline levels is believed to be caused by CO2, the amount of which in the atmosphere has surged due to large consumption of fossil fuels, among other factors.

A group of scientists, led by Takashi Midorikawa of the Meteorological Research Institute in Tsukuba, Ibaraki Prefecture, has checked the pH readings of surface seawater off the Kii Peninsula at 30 degrees north latitude that have been made since 1986. They have found that the pH has dropped by 0.04 during this period, a considerable change. Such ocean acidification has been observed elsewhere as well, such as off Hawaii.

Midorikawa’s group used data collected on a survey ship that observed seawater from near Japan down to near the equator, following a line of 137 degrees east longitude. The data were provided by the Meteorological Agency, which has long monitored ocean pH twice every year as part of its regular duties.

iStockAnalyst, 21 November 2009. Full article.

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