Director of the USGS Marcia McNutt paused for reflection and then answered unequivocally "ocean acidification." Her response came after a thorough plenary address to the American Association for the Advancement of Science Annual Meeting, during which she had recounted alarming trends in ocean shoreline retreat, rising sea level and the drowning of shoreline wetland areas, expansion of hypoxia or dead zones where rivers meet the oceans, and the deleterious effects of mercury in oceanic environments. Rising carbon dioxide levels in the atmosphere are to blame for the increasing acidity of ocean waters, and the impact on living organisms is compounded by rising temperature, said McNutt.
Why should you care? The oceans cover 71% of earth's surface and are home to tens of thousands of species, a large percentage of which are still to be described. The inter-dependencies of oceanic ecosystems make them especially vulnerable to negative inputs anywhere in the world's seas and oceans. Scientists can hardly fathom the untold loss in biodiversity and the concomitant impact on species that rely on healthy oceans for food and breeding. Increasing acidity has both biological and physical impacts, including altering sound and light propagation qualities of ocean water (Doney, et al., introductory essay to Oceanography, Dec. 2009)
Learn more with the freely accessible special issue of Oceanography (Dec. 2009). For a compelling summary of why a healthy ocean matters, read Carolyn Thoroughgood's letter (The Oceanography Society President's Letter, a regular column of Oceanography).
More information: The Ocean Acidification Network.
Seasick: ocean change and the extinction of life / Alanna Mitchell.