Acid Rain Destroying Coastal Waters
Pastor Dale Morgan
Acid Rain Destroying Coastal Waters*
Farming, livestock husbandry, and the combustion of fossil fuels cause
excess sulfur dioxide, ammonia, and nitrogen oxides to be released to
the atmosphere, where they are transformed into nitric acid and sulfuric
acid. Though much of that acid is deposited on land (since it does not
remain in the air for long), some of it can be carried in the air all
the way to the coastal ocean.
by Staff Writers
Bell House MS (SPX) Sep 12, 2007
The release of sulfur and nitrogen into the atmosphere by power plants
and agricultural activities plays a minor role in making the ocean more
acidic on a global scale, but the impact is greatly amplified in the
shallower waters of the coastal ocean, according to new research by
atmospheric and marine chemists.
Ocean "acidification" occurs when chemical compounds such as carbon
dioxide, sulfur, or nitrogen mix with seawater, a process which lowers
the pH and reduces the storage of carbon.
Ocean acidification hampers the ability of marine organisms-such as sea
urchins, corals, and certain types of plankton-to harness calcium
carbonate for making hard outer shells or "exoskeletons." These
organisms provide essential food and habitat to other species, so their
demise could affect entire ocean ecosystems.
The findings were published this week in the online "early edition" of
the Proceedings of the National Academy of Sciences; a printed version
will be issued later this month.
"Acid rain isn't just a problem of the land; it's also affecting the
ocean," said Scott Doney, lead author of the study and a senior
scientist in the Department of Marine Chemistry and Geochemistry at the
Woods Hole Oceanographic Institution (WHOI). "That effect is most
pronounced near the coasts, which are already some of the most heavily
affected and vulnerable parts of the ocean due to pollution,
over-fishing, and climate change."
In addition to acidification, excess nitrogen inputs from the atmosphere
promote increased growth of phytoplankton and other marine plants which,
in turn, may cause more frequent harmful algal blooms and eutrophication
(the creation of oxygen-depleted "dead zones") in some parts of the ocean.
Doney collaborated on the project with Natalie Mahowald, Jean-Francois
Lamarque, and Phil Rasch of the National Center for Atmospheric
Research, Richard Feely of the Pacific Marine Environmental Laboratory,
Fred Mackenzie of the University of Hawaii, and Ivan Lima of the WHOI
Marine Chemistry and Geochemistry Department.
"Most studies have traditionally focused only on fossil fuel emissions
and the role of carbon dioxide in ocean acidification, which is
certainly the dominant issue," Doney said. "But no one has really
addressed the role of acid rain and nitrogen."
The research team compiled and analyzed many publicly available data
sets on fossil fuel emissions, agricultural, and other atmospheric
emissions. They built theoretical and computational models of the ocean
and atmosphere to simulate where the nitrogen and sulfur emissions were
likely to have the most impact. They also compared their model results
with field observations made by other scientists in the coastal waters
around the United States.
Farming, livestock husbandry, and the combustion of fossil fuels cause
excess sulfur dioxide, ammonia, and nitrogen oxides to be released to
the atmosphere, where they are transformed into nitric acid and sulfuric
acid. Though much of that acid is deposited on land (since it does not
remain in the air for long), some of it can be carried in the air all
the way to the coastal ocean.
When nitrogen and sulfur compounds from the atmosphere are mixed into
coastal waters, the researchers found, the change in water chemistry was
as much as 10 to 50 percent of the total changes caused by acidification
from carbon dioxide.
This rain of chemicals changes the chemistry of seawater, with the
increase in acidic compounds lowering the pH of the water while reducing
the capacity of the upper ocean to store carbon.
The most heavily affected areas tend to be downwind of power plants
(particularly coal-fired plants) and predominantly on the eastern edges
of North America, Europe, and south and east of Asia.
Seawater is slightly basic (pH usually between 7.5 and 8.4), but the
ocean surface is already 0.1 pH units lower than it was before the
Industrial Revolution. Previous research by Doney and others has
suggested that the ocean will become another 0.3 to 0.4 pH units lower
by the end of the century, which translates to a 100 to 150 percent
increase in acidity.
Funding for this research was provided by the National Science
Foundation, the National Aeronautics and Space Administration, and the
National Oceanic and Atmospheric Administration.
Woods Hole Oceanographic Institution is a private, independent
organization in Falmouth, Mass., dedicated to marine research,
engineering, and higher education. Established in 1930 on a
recommendation from the National Academy of Sciences, its primary
mission is to understand the oceans and their interaction with the Earth
as a whole, and to communicate a basic understanding of the ocean's role
in the changing global environment.