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Increasing atmospheric CO2 and eutrophication combine to acidify coastal bottom waters

Published on: 02/15/2012
Research Area(s): Coastal Change
Region(s) of Study: Waterbodies / Gulf of Mexico

Dissolution of carbon dioxide (CO2) from rising atmospheric CO2 is acidifying ocean water;but a second environmental problem, eutrophication, is having a similar effect in coastal bottomwaters. This occurs because anthropogenic inputs of nutrients fuel massive algal blooms,which deplete bottom waters of oxygen (O2) and release CO2 when the organic matter fromthese blooms is respired by bacteria.

Based on a biogeochemical model, these CO2 inputs arepredicted to decrease current pH values by 0.25 to 1.1 units, effects that increase with decreasingtemperature and salinity. The model predictions were verified by pH data from hypoxic zones inthe northern Gulf of Mexico and Baltic Sea, two well known eutrophic systems. These decreasesin pH are well within the range that adversely impacts marine fauna.

Model calculations showthat the acidification from respiratory CO2 inputs interacts in a complex fashion with that fromincreasing atmospheric CO2, and that these pH effects are more than additive at intermediateto higher temperatures. These synergistic interactions have important biological implicationsin a future world with increasing atmospheric CO2, higher anthropogenic inputs of nutrients,and rising temperatures from CO2-linked global warming.

These findings will be presented in aposter at the Ocean Sciences Meeting in Salt Lake City, February 15-19.

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