A planetary experiment: Ocean acidification and biology

Ocean acidification is a relatively newly recognized threat to marine ecosystems. Even coral reef scientists, many of whom are now feverishly investigating the effects of changing seawater chemistry, ranked ocean acidification as 36th out of 40th potential threats to coral reef ecosystems in 2004 [1]. Recently, the magnitude of the shifting chemical balance in the ocean has become strikingly apparent [2].

Atmospheric carbon dioxide concentrations are predicted to exceed 500 ppmv by 2100 [3]. Today, atmospheric carbon dioxide concentration is above 380 parts per million, a value not seen in the past 740,000 years, conservatively [4]. The ocean functions as a massive carbon sink and absorbs up to a third of atmospheric carbon. As carbon dioxide dissolves into seawater, it reacts to form carbonic acid, which dissociates to form bicarbonate ions and protons. The protons react with carbonate ions, converting them to bicarbonate as well. This reduces the availability of carbonate ions in seawater, a principal component of calcium carbonate–which what many calcifying marine organisms make their shells or skeletons out of. The ocean is becoming less basic, as these reactions also lower oceanic pH. The average surface ocean pH has decreased 0.1 pH units since the preindustrial era to today [5].

The ocean stands to become more acidified. Surface ocean pH stands to drop another 0.3 -0.4 units by the end of the century (remember that pH is measured on a log scale), under the IPCC ‘business-as-usual’ scenario of 800 ppm by 2100 [2].

This is a problem. Especially if you’re a marine organism whos produce calcium carbonate in some form.

EPA: States should list coastal waters as impaired due to rising ocean acidification

States with coastal water that is becoming more acidic because of carbon dioxide should list them as impaired under the Clean Water Act, the U.S. Environmental Agency said.

The federal agency’s memo Monday to states recognizes carbon dioxide as not only an air pollutant but a water pollutant, and notes the serious impacts that ocean acidification can have on aquatic life.

Ocean acidification refers to the decrease in the alkalinity of oceans, which is caused by the absorption of excess carbon dioxide from the atmosphere. As water becomes more acidic, scientists have raised concern about dissolving coral reefs and potential effects on fish and other sea life.

“Ocean acidification is one of the biggest threats to our marine environment,” said Miyoko Sakashita, a senior attorney at Center for Biological Diversity. This EPA action “really gave the green light to using the Clean Water Act to address ocean acidification,” she said.