Ocean Acidification

          In this episode of the KPFA radio program, Against the Grain, Meg Chadsey of Washington Sea Grant explains the effects of ocean acidification on the marine environment.  At the beginning of the interview, Chadsey explains the basics: 

MC:   Since the Industrial Revolution, which was about a hundred and fifty years ago, roughly, we have been burning fossil fuels.  And the amount of carbon that’s released when you convert coal and gas and oil into carbon dioxide is really significant, and that probably accounts for about ninety percent of our annual carbon dioxide emissions as fossil fuel combustion.  Another ten percent comes from deforestation.  So when we’re cutting down forests to increase the agricultural area, for example, and we’re burning those forests, that also releases carbon dioxide that has been stored long-term as wood, as biomass, into the atmosphere as CO2.  So those are the two major sources of carbon dioxide: fossil fuels and deforestation.

     
      Chadsey says that every year about 10 billion metric tons of CO2 is emitted and disperse throughout the biosphere a result of human activity.  Seventy-five percent goes into the atmosphere, and roughly twenty-five percent enters the ocean.  The fast rate at which carbon dioxide is entering the seas prevents the currents for diluting it thoroughly, so acidification is occurring largely near the surface of the world’s oceans.  She goes onto to talk about the direct effect that increased acidification breaks down skeletal and shells structure of calcium carbonate-based marine organisms (she gives the example of a piece of chalk dissolving in lemon juice).    C.S Soong, host of Against the Grain, lists some of the marine creatures that have calcium carbonate skeletons and shells that are being affected by increased acidification of the oceans:  oysters, crabs, mussels, scallops, clams, lobsters, shrimp, abalone, sea stars, corals, barnacles, sand dollars, sea cucumbers.  Chadsey responds that if these marine animals, which serve as a large base for much of the food web, then we are all in deep shit.

 
Image from: http://www.worldwildlife.org/threats/bycatch

Here are some other interesting excerpts of the show:

(31 min.) CS:  …Should we be concerned then – just following up on your last answer – that some marine species will go extinct because of acidification?  Are there any predictions in that regard – how many species might go extinct, how quickly?

MC:  I think we should absolutely be concerned about extinction. I’m not going to be able to give you hard numbers for predictions, but I would say people are very concerned, and one of the reasons they’re concerned is because there are precedents in Earth’s deep geologic history for mass extinctions related to acidification of the ocean.  What we’re experiencing now is not the first time that the Earth’s oceans have become much more acidic.  Right now our oceans are acidifying at a relatively rapid pace compared to past geological events, so the problem actually might be more severe for us than it was in the past.  But we can look at the past geologic record and see what happened when similar acidification events occurred, and unfortunately things did not go well.  During one of the earlier acidification events, up to eighty-percent of calcifying foraminifera – which are a type of small organism, a shell forming plankton species – up to eight percent of all foraminiferous species went extinct.  Also the types of corals that we associate with coral reefs – hard-bodied corals that build colonies and form these massive reefs – those also went extinct at a tremendous rate, and they actually had to recover.  The corals that we know today have had millions of years to re-evolve and build back up to previous levels, but they were almost wiped-out.  And I should say that the rate of acidification, the rate at which oceans are becoming more acidic now is probably about a hundred times faster than the rate at which oceans acidified during these previous extinction events in deep Earth history.  So, if anything we’re probably looking at a worse scenario.

Image from: http://oceansrock.org/wp-content/uploads/2011/09/dyingreef26.jpg

(46 min) CS: …I read somewhere that the acidic, CO2 rich water that surfaces off the U.S west coast – California, Oregon, Washington – that’s actually a result of CO2 that’s entered the ocean decades ago, so in other words: even if emissions halted immediately, and you can correct me if I’m wrong, west coast sea chemistry would worsen for several decades before plateauing, which brings to my mind the question: is it too late?  Is there so much CO2 already in the oceans that we can really cut-in to the acidification process in a meaningful way?

MC:  I’m glad you raised that point C.S.  You’re exactly right – that we’re short of locked-in to a future of increasing acidity for the next several decades, even if we were to halt emissions today, which of course would be practically impossible to do.   And the reason that’s occurring is because of the way water masses move around in the Pacific Ocean.  The water that’s currently welling up on our coastline now is a layer of deeper seawater that basically was last at the surface thirty to fifty years ago when it was way up in the north pole, and then it sinks and travels and comes up on our coast.  So the amount of CO2 in the water that’s welling up on the Pacific coast now reflects the atmospheric concentration from thirty to fifty years ago, which is of course less than what it is today.  But it also carries a natural burden of CO2 that’s generated by living organisms.  The whole time that water’s transiting the in ocean, there are animals that consume oxygen and exhale CO2, even underwater – they’re just like us, they pull the oxygen out of the water and they exhale CO2.  So they’re adding CO2 during that time, and that’s part of the CO2 that’s causing a problem on our coastline right now. 

But you asked, because of things like that, is it…is everything lost, is there nothing we can do?  Absolutely I do not feel that way.  Things can get a lot worse than they are today, and I’ve been surprised to see that a large part of the CO2 emissions that we’re dealing with now, that are in our atmosphere, have happen in my lifetime.  You know when people talk about human activity contributing to carbon dioxide emissions they also start from the Industrial Revolution which was a hundred and fifty years ago.  But if you look at the graphs that show the rate of emissions, things have really picked-up since the early seventies, in the late sixties, and they’re picking-up at an ever increasing rate, so it actually is really important to keep trying to stall, to stop, and reverse what we’re doing now, because a year’s worth of emissions in the twenty-first century are a lot more than a year’s worth of emissions thirty to forty years ago.

Alexis Rockman, Manifest Destiny