Saturday, June 11, 2011

Are phytoplankton disappearing from the ocean?

  In 2010, a spectacular claim was made in the prestigious journal Nature that the population of phytoplankton in the ocean had declined by something like 40% since 1950  (Boyce et al., Global Phytoplankton decline over the past century, Nature Vol 466 pp 591-596, 29 July 2010). 

At the time, one of the things I was working on was a way to absorb oil spills and to clean up oil contaminated seawater.  You may recall that the BP Deep Horizon disaster had occurred at that time, and I took a centrifuge (I would tell you who donated it, but the company wishes to remain anonymous) down to Port Arthur Texas to work with a company interested in remediating contaminated seawater.  Although where we were, the beaches were spectacularly clean and fishing was excellent, we were rightly concerned about the impact on ocean life.  But we knew the Gulf would survive even this serious spill.  By contrast the claims of Boyce et al were that FORTY PERCENT of the plankton were missing from ALL THE OCEANS OF THE WORLD.  This was such as serious claim that it dwarfs all concerns about overfishing or spilling oil or anything else.  Fish and sea animals can't survive without phytoplankton and I doubt whether life on land including humans could survive very long if the phytoplankton were going extinct at such an alarming rate.  It's hard to quantify the significance of billions of tons of ocean life,  but let's such say it would be orders of magnitude more serious than any hurricane or oil spill or other event that we have experienced.  

Boyce et al were convinced that this mass extinction had occurred due to the ravages of global warming.  I  doubted that, based on the following reasoning:  suppose there were a lake somewhere with a healthy population of phytoplankton.  Suppose overnight the temperature rose from 55 degrees Fahrenheit to 56.  Does that kill half the plankton in the lake?  Not likely!  Even less likely if you give the plants 60 years to make the adjustment. 

Still I was surprised that many people seemed content to a) accept the claims of Boyce et al, and b) didn't seem too concerned about it.  My feeling, in a nutshell, was that the scientific community needed to find out whether it was true or not, and if it were true it was time to push the panic button.

But over the past year, other articles have appeared which suggest that the orginal contention of Boyce et al may be due to a ghastly error.  Rykaczewski and Dunne published a rebuttal in Nature (A Measured Look at Ocean Chlorophyll trends, Nature Vol 472, pp E5-E6, 14 April 2011).  They suggest the Boyce's data was in error because of changes in sampling methodology and analysis.  A similar note appeared in Nature from Ohlman (Nature 466, 591 - 596 (7306)
Published online: 2010-07-29). 

Phew!  So maybe the reason everyone seemed unconcerned about the data was due to its fishy smell. 

Does this mean that the world is off the hook?  Not necessarily.  I still remain very concerned about ocean pollution and curious about the attitudes of my friends and colleagues.  A number of us were outraged, rightly so, by the BP Horizon spill last year.  But few people complain about the amount of pollution that we dump into the same body of water.  The United States is the most powerful agricultural economy on earth, and most of the petrochemical fertilizer runoff from that economy winds up draining into the Gulf via the Mississippi and other rivers.  It is millions of tons per year, and has resulted in enormous dead zones near the mouth of the Mississippi in which life can not be supported. If you go to the Florida Panhandle and are lucky enough to get a hotel with a view of the ocean, you may be surprised to find that it is now green.  The ocean is supposed to be blue, folks.  The reason is that in this area all that fertilizer has caused phytoplankton to proliferate (the opposite effect claimed by Boyce et al, by the way).  You can definitely see it.  And yes, changing the color of the ocean means that there are other effects as well.  Some years ago I wrote an article explaining that greener water might absorb sunlight more effectively near the surface, and that there could be some effect on climate change.  Some of my friends in the business are aware of that now and trying to incorporate such effects into global climate models.  

I believe that we should seek the means to recover millions of tons of chemicals from rivers in the US.  Our emphasis is mainly on stopping pollution at its source, which is a good approach, but in the case of the Mississippi and other rivers, we just have to admit that millions of tons of chemicals are getting into the water anyway, and it makes sense to figure out ways to clean it up.

BAre phytoplankton increasing due to massive quantities of fertilizer being dumped into the ocean? Or are they vanishing? We need the right answers to feed into the computer models that tell how our climate is behaving.

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