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Ocean Acidification

Ocean Acidification

Over the past 250 years, rapid growth in the burning of fossil fuels and changes in land use have caused a dramatic rise in CO2 emissions. About one quarter of these human-generated emissions – some 550 billion tons of CO2 - have been absorbed by the oceans. This CO2 has an acidifying effect when dissolved in seawater. As a result the average acidity of the surface ocean has increased about 30% since 1750. Ocean acidification can be more severe in areas where decaying algal blooms- sometimes exacerbated by human impacts such as nutrient runoff- contribute to high CO2, low-oxygen conditions (hypoxia) further increasing acidity.

Many ocean life processes, including photosynthesis, growth, respiration, reproduction, and behavior are sensitive to changes in CO2 and pH. Ocean acidification leads to conditions that are chemically corrosive and especially problematic for shelled organisms but also has the potential to affect a wide range of other ocean life, from seagrasses to fish, in many different ways.

The current rate of acidification is nearly 10 times faster than any time in the past 50 million years, outpacing the ocean’s capacity to restore oceanic pH and carbonate chemistry. This rate of change also gives marine organisms, marine ecosystems, and humans less time to adapt, evolve, or otherwise adjust. At current rates of global CO2 emissions, the average acidity of the surface ocean is expected to increase by 100–150% over pre-industrial levels by 2100.

Authored by Jeff Behan, Science Policy Research Analyst, Institute for Natural Resources