Comments on: Guest post on gulf hypoxia (GH) http://lacoastpost.com/blog/?p=7454 Fri, 03 Sep 2010 21:11:19 +0000 hourly 1 http://wordpress.org/?v=3.0 By: Piers Chapman http://lacoastpost.com/blog/?p=7454&cpage=1#comment-3546 Piers Chapman Sat, 16 May 2009 21:09:02 +0000 http://lacoastpost.com/blog/?p=7454#comment-3546 Actually Don, we didn't say this. Of course it is true to say that if there is no nutrient supply, there is no production, but also, without the stratification, there is no hypoxia. So respiration of organic matter is the prime "cause" of hypoxia. What we did say was that we are essentially arguing over the importance of different controls of hypoxia, and as I said above, the relative importance of the stratification becomes greater the further west you go, since this allows respiration below the pycnocline to continue for longer before oxygen can be replenished from the surface layer. Actually Don, we didn't say this. Of course it is true to say that if there is no nutrient supply, there is no production, but also, without the stratification, there is no hypoxia. So respiration of organic matter is the prime "cause" of hypoxia. What we did say was that we are essentially arguing over the importance of different controls of hypoxia, and as I said above, the relative importance of the stratification becomes greater the further west you go, since this allows respiration below the pycnocline to continue for longer before oxygen can be replenished from the surface layer.

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]]> By: Don Boesch http://lacoastpost.com/blog/?p=7454&cpage=1#comment-3496 Don Boesch Sat, 09 May 2009 14:12:16 +0000 http://lacoastpost.com/blog/?p=7454#comment-3496 Piers, you're right, it was not Bianchi et al., but the paper by you and and Gil that invented the straw man fallacy that nutrients, and only nutrients, control hypoxia. You reprised it again here in your guest post. My point is that I know of no scientists who ever suggested this to be the case in the first place. However, just because one can easily knock down this straw man by showing that stratification is also necessary does not mean, logically, that nutrients play no role in hypoxia farther west of the Atchafalaya. In our Eos article we address this issue: "Stratification alone is insufficient to deplete the oxygen inventories of waters beneath the density discontinuity; the consumption of oxygen faster than its resupply is also required [Hetland and DiMarco, 2007]. . . . the labile organic matter supporting benthic respiration must be derived predominantly from planktonic production either from the overlying surface water or, through advection, from highly productive waters just inshore." This surface planktonic production is clearly supported by riverine nutrients, particularly by recycled nutrients that would not be reflected in high surface concentrations. Piers, you're right, it was not Bianchi et al., but the paper by you and and Gil that invented the straw man fallacy that nutrients, and only nutrients, control hypoxia. You reprised it again here in your guest post. My point is that I know of no scientists who ever suggested this to be the case in the first place. However, just because one can easily knock down this straw man by showing that stratification is also necessary does not mean, logically, that nutrients play no role in hypoxia farther west of the Atchafalaya. In our Eos article we address this issue: "Stratification alone is insufficient to deplete the oxygen inventories of waters beneath the density discontinuity; the consumption of oxygen faster than its resupply is also required [Hetland and DiMarco, 2007]. . . . the labile organic matter supporting benthic respiration must be derived predominantly from planktonic production either from the overlying surface water or, through advection, from highly productive waters just inshore." This surface planktonic production is clearly supported by riverine nutrients, particularly by recycled nutrients that would not be reflected in high surface concentrations.

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]]> By: Piers Chapman http://lacoastpost.com/blog/?p=7454&cpage=1#comment-3455 Piers Chapman Fri, 01 May 2009 21:20:25 +0000 http://lacoastpost.com/blog/?p=7454#comment-3455 Having reread our article in EOS, I'm still trying to see how Don manages to find support for his statement "It was Piers and his co-authors in their Eos forum who offered the statement that “nutrients, and only nutrients, control everything to do with Gulf of Mexico hypoxia,” not those accused of this dogma. " Gil Rowe and I suggested several years ago that the importance of surface stratification increases the further west you go, because there are essentially no nutrients in the surface layer in summer once you get west of Atchafalaya Bay, and nothing we have seen in numerous cruises since then has caused us to change our minds on this. Having reread our article in EOS, I'm still trying to see how Don manages to find support for his statement "It was Piers and his co-authors in their Eos forum who offered the statement that “nutrients, and only nutrients, control everything to do with Gulf of Mexico hypoxia,” not those accused of this dogma. " Gil Rowe and I suggested several years ago that the importance of surface stratification increases the further west you go, because there are essentially no nutrients in the surface layer in summer once you get west of Atchafalaya Bay, and nothing we have seen in numerous cruises since then has caused us to change our minds on this.

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]]> By: Bob Howarth http://lacoastpost.com/blog/?p=7454&cpage=1#comment-3442 Bob Howarth Wed, 29 Apr 2009 21:07:29 +0000 http://lacoastpost.com/blog/?p=7454#comment-3442 The Gulf of Mexico is a complicated place, but a number of excellent scientists have worked hard to unravel the causes of the Gulf hypoxia for a couple of decades now, with some of the finest efforts led by Nancy Rabalais, Don Boesch, and their colleagues. As a member of the EPA Science Advisory Board's Panel on Gulf Hypoxia, I agree totally that the solution to hypoxia is to reduce the flows of nitrogen and phosphorus down the Mississippi. Most of these nutrients come from agriculture in the upper midwest, so the solution must begin there. Unfortunately, as Pier alludes, the rapid increase in production of biofuels in the US is aggravating the problem. Models suggest that if the US meets its Congressionally mandated target for producing ethanol from corn, nitrogen loads down the Mississippi will increase by more than 30%, significantly increasing the size of the hypoxia area. For more details on this and other environmental issues with producing biofuels, see our report published earlier this month from the International SCOPE Biofuels Project, available on line at <a href="http://cip.cornell.edu/biofuels/" target="_blank">http://cip.cornell.edu/biofuels/</a> Bob Howarth, Chair of the International SCOPE Biofuels Project, Cornell University, Ithaca, NY The Gulf of Mexico is a complicated place, but a number of excellent scientists have worked hard to unravel the causes of the Gulf hypoxia for a couple of decades now, with some of the finest efforts led by Nancy Rabalais, Don Boesch, and their colleagues. As a member of the EPA Science Advisory Board's Panel on Gulf Hypoxia, I agree totally that the solution to hypoxia is to reduce the flows of nitrogen and phosphorus down the Mississippi. Most of these nutrients come from agriculture in the upper midwest, so the solution must begin there. Unfortunately, as Pier alludes, the rapid increase in production of biofuels in the US is aggravating the problem. Models suggest that if the US meets its Congressionally mandated target for producing ethanol from corn, nitrogen loads down the Mississippi will increase by more than 30%, significantly increasing the size of the hypoxia area. For more details on this and other environmental issues with producing biofuels, see our report published earlier this month from the International SCOPE Biofuels Project, available on line at http://cip.cornell.edu/biofuels/

Bob Howarth, Chair of the International SCOPE Biofuels Project, Cornell University, Ithaca, NY

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]]> By: Matt Rota http://lacoastpost.com/blog/?p=7454&cpage=1#comment-3441 Matt Rota Wed, 29 Apr 2009 16:11:48 +0000 http://lacoastpost.com/blog/?p=7454#comment-3441 The take-home message as I see it is that the only real way to reduce the size of the dead zone is to reduce the nitrogen and phosphorus pollution getting into the Mississippi-Atchafalaya River system. As Dr. Chapman sates, agricultural interests,and thus agricultural states have been and will continue to be very resistant to any reduction to nitrogen and phosphorus if this would have any impact on row-crop, fertilizer intensive agriculture. Because of resistance coming from upper basin states, Louisiana needs to become a real advocate for reducing the size of the dead zone. In my view, Louisiana has completely failed in this advocacy. If Louisiana, lead by our Governor, does not make this a national issue, we will continue to see massive dead zones off our coast... The take-home message as I see it is that the only real way to reduce the size of the dead zone is to reduce the nitrogen and phosphorus pollution getting into the Mississippi-Atchafalaya River system. As Dr. Chapman sates, agricultural interests,and thus agricultural states have been and will continue to be very resistant to any reduction to nitrogen and phosphorus if this would have any impact on row-crop, fertilizer intensive agriculture. Because of resistance coming from upper basin states, Louisiana needs to become a real advocate for reducing the size of the dead zone. In my view, Louisiana has completely failed in this advocacy. If Louisiana, lead by our Governor, does not make this a national issue, we will continue to see massive dead zones off our coast…

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]]> By: Don Boesch http://lacoastpost.com/blog/?p=7454&cpage=1#comment-3439 Don Boesch Wed, 29 Apr 2009 13:06:03 +0000 http://lacoastpost.com/blog/?p=7454#comment-3439 Wow, I was just fine with Piers' post up until the point he began accusing those (including, presumably, the EPA Hypoxia Advisory Panel <a href="http://epa.gov/msbasin/tfproducts.htm" target="_blank">http://epa.gov/msbasin/tfproducts.htm</a> ) who advocate, based on the scientific evidence, action to control nutrient pollution in order to reduce hypoxia as guilty of politics and dogma. I couldn't agree more with his closing statement and would hope all parties resist the temptation to sow confusion about the causes of and solutions for hypoxia. We can see how such denialist-sown confusion has delayed action on global climate change. From the earliest publications in the 1980s, the effects of water column stratification and winds on the severity, distribution and duration of hypoxia were well recognized. It was Piers and his co-authors in their Eos forum who offered the statement that “nutrients, and only nutrients, control everything to do with Gulf of Mexico hypoxia,” not those accused of this dogma. But, as Piers points out, there is "absolutely no doubt" that without the large nutrient input (mainly nitrogen) from the rivers there would be no hypoxia in the northern Gulf. Further, he states that because we have no hope of controlling either freshwater inflows or winds, the only practical way to reduce Gulf hypoxia is through reducing the nutrient concentrations in the Mississippi and Atchafalaya by a pretty large percentage. Amen, that's really all we so-called political dogmatists have ever said. In our recent Eos article discussed in Len's April 9 blog, we clarified several of the scientific issues that Piers lists as unclear. The one issue that I would agree remains highly relevant to integrated environmental management of Louisiana coastal ecosystems is the effect on hypoxia of river diversions. Bill Mitch, John Day and colleagues showed in 2001 (BioScience 51: 373) that diversions through wetlands could conceivably reduce nitrogen loads by about 10%, but every little bit helps. However, diverting large flows to different parts of the inner shelf could either increase or decrease hypoxia rather considerably, depending on where the fresh water and nutrients are injected. It seem to me that this would be a very productive area of scientific discourse and assessment, rather that pointless debates about whether nutrient loads must be reduced to shrink hypoxia. At this point, this is a no brainer. Wow, I was just fine with Piers' post up until the point he began accusing those (including, presumably, the EPA Hypoxia Advisory Panel http://epa.gov/msbasin/tfproducts.htm ) who advocate, based on the scientific evidence, action to control nutrient pollution in order to reduce hypoxia as guilty of politics and dogma. I couldn't agree more with his closing statement and would hope all parties resist the temptation to sow confusion about the causes of and solutions for hypoxia. We can see how such denialist-sown confusion has delayed action on global climate change.

From the earliest publications in the 1980s, the effects of water column stratification and winds on the severity, distribution and duration of hypoxia were well recognized. It was Piers and his co-authors in their Eos forum who offered the statement that “nutrients, and only nutrients, control everything to do with Gulf of Mexico hypoxia,” not those accused of this dogma. But, as Piers points out, there is "absolutely no doubt" that without the large nutrient input (mainly nitrogen) from the rivers there would be no hypoxia in the northern Gulf. Further, he states that because we have no hope of controlling either freshwater inflows or winds, the only practical way to reduce Gulf hypoxia is through reducing the nutrient concentrations in the Mississippi and Atchafalaya by a pretty large percentage. Amen, that's really all we so-called political dogmatists have ever said.

In our recent Eos article discussed in Len's April 9 blog, we clarified several of the scientific issues that Piers lists as unclear. The one issue that I would agree remains highly relevant to integrated environmental management of Louisiana coastal ecosystems is the effect on hypoxia of river diversions. Bill Mitch, John Day and colleagues showed in 2001 (BioScience 51: 373) that diversions through wetlands could conceivably reduce nitrogen loads by about 10%, but every little bit helps. However, diverting large flows to different parts of the inner shelf could either increase or decrease hypoxia rather considerably, depending on where the fresh water and nutrients are injected. It seem to me that this would be a very productive area of scientific discourse and assessment, rather that pointless debates about whether nutrient loads must be reduced to shrink hypoxia. At this point, this is a no brainer.

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