There's a
new NAS report out that notes an increased danger from acid rain for coastal waters especially when combined with increased atmospheric CO2 concentrations.
The release of sulfur and nitrogen into the atmosphere by power plants and agricultural activities--commonly referred to as acid rain--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 oceans, according to new research.
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.
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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. It 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.
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In addition to acidification, excess nitrogen input from the atmosphere likely promotes the overgrowth of phytoplankton and other marine plants that have caused more frequent harmful algal blooms and eutrophication (including the creation of oxygen-depleted dead zones) in the oceans.
I read a journal article several years ago that suggested that red tide dinoflaggelates tended to thrive in lower pH waters. I wonder if increased oceanic CO2 concentrations over bicarbonate favor those organisms. Some of the current research on Harmful Algal Blooms (HABs) in Florida is focused on increases in iron in the waters from aeolian transport in dust clouds. There appears to be a link between Trichodesmium, a nitrogen fixing cyanobacteria, and HABs. The Tricho need the iron to uptake inorganic nitrogen. The theory is that they exude certain products that the dinoflagellates are able to utilize as nutrient sources. I wonder if acid rain is also playing into the picture since some of the areas where we've seen some pretty large blooms here are near large coal fired power plants and population centers.