Southern Ocean Acidification

Most who know something about ocean acidification learn about its effects on coral reefs.  It is a leading contributor to coral bleaching.  It is important to understand that the effects of ocean acidification extend to well beyond the tropics, to the Southern Ocean.  

What is ocean acidification?  Many people speak of the ocean as an immense carbon sink, absorbing much of the increased levels of carbon dioxide (CO₂) in the atmosphere.  Ocean acidification is the price of that sink.  Ocean acidification is a chemical process triggered by having a great influx of carbon dioxide into a marine ecosystem.  Naturally the ocean has a balance of bicarbonate (HCO₃^-), and carbonate (CO₃^-) ions.  When there is an increased flux of carbon dioxide into a marine system there is an upset to the balance of bicarbonate and carbonate where bicarbonate becomes dominant.  Zooplankton use the carbonate ions to help form their shells.  With less carbonate available, zooplankton lack the necessary elements to form their shells, which are imperative to their survival.  With fewer zooplankton, the bottom of the food chain is depleted, and there is a domino effect directly to the top of the food chain.  

Additionally, relatively larger organisms like mollusks also rely on this balance of carbonate and bicarbonate in the ocean.  When there is less carbonate available, mollusks create weaker shells and their chances of survival are severely diminished.  This may one day have severe effects on people who subsist on mollusks for food or income.  

Back to the southern ocean…there is a champagne effect with a marine system’s ability to hold CO₂.  That is to say, just as Champagne stays fizzier longer when refrigerated, oceans hold more CO₂ when they are colder.  This makes the frigid Southern Ocean a primary target for ocean acidification observation. 

Dr. Donna Roberts and Team Acid, a group of scientists from Australia, disembarked a few weeks ago to study the effects of ocean acidification on the Southern Ocean.  They are collecting samples of plankton across the waters of the Southern Ocean, from Australia to the Antarctic.  This will help establish a baseline for other similar future studies so that scientists may see the effects of ocean acidification over time. 

As said earlier, acidification affects the marine food chain from the bottom, up.  An impact on polar food chains can have global ramifications, especially for the fishing industry.  With the majority of US fishery landings deriving from high latitude seas, it is important to be able to predict and compensate for our impact on these systems.  

As Dr. Roberts put it, “Team Acid is focusing on the little things to illuminate some of the biggest issues facing the planet, particularly the increasingly worrying picture of impacts on Southern Ocean plankton in a high CO₂ world.”

You can read more about Dr. Roberts and Team Acid here…

http://www.rtcc.org/nature/letter-from-antarctica-ocean-acidification-at-the-south-pole/