Nice presentation. I am not disputing the appearance of dead zones. We have been seeing them in the mainstem of the Chesapeake during the last few years. The 'excessive' algae growth model is probably appropriate in the Chesapeake Bay, possibly the Baltic, as they tend to enclosed & relatively small areas, where nutrient concentrations can escalate rapidly. My question is that model sufficient to explain dead zones encountered in well cleanesed open sea/ocean areas, where the nutrient conc would not escalate that much. SO the question is there another/other factors acting outside of the dead algae model, or such factors acting synergistically. The more concrete answer is: are there studies that quantify the nutrient levels, the expected algae that would generate, and the O2 needed to decompose that biomass of algae. Esat Atikkan
Ned Gardiner <[EMAIL PROTECTED]> wrote: In case anyone is teaching a class on this topic, please consider directing your students to this news brief we prepared in November, 2006. http://sciencebulletins.amnh.org/?sid=b.s.dead_zones.20061113&src=l --- William Silvert wrote: > I don't have the material at hand, but I believe > that these calculations > have been done for the Baltic. There is a large and > growing anoxic zone > which is attributed to agricultural runoff, and I am > almost certain that the > connection has been established through quantitative > models. > > And I see no reason why these effects should be > localised. > > Bill Silvert > > ----- Original Message ----- > From: "Esat Atikkan" > To: > Sent: Wednesday, February 13, 2008 7:04 PM > Subject: Re: Let's talk about the Gulf dead zone and > water nutrients > > > > The 'bacteria decomposing dead algae' thus > depleting O2 model could > > possibly explain local hypoxia/anoxia. However > when the O2 depleted area > > becomes as broad as that seen in the Gulf of > Mexico or in the Pacific > > Ocean, off Oregon, that model may be lacking. > > > > One approach would be to estimate the actual > amount of such algae > > reaching the bottom, and the quantity of O2 it > would take to decompose > > (via bacteria). > > > > Is anyone aware of such a quantification? > > > > Esat Atikkan > > > > William Silvert wrote: > > Just to hit the first point, the reason why > hypereutrophic waters tend to > > have benthic dead zones is because they produce > too much algae, which sink > > rather than being eaten and accumulates on the > bottom. There it is > > degraded > > by bacteria, and this is the process that sucks up > the oxygen. > > > > Bill Silvert > ____________________________________________________________________________________ Never miss a thing. Make Yahoo your home page. http://www.yahoo.com/r/hs --------------------------------- Be a better friend, newshound, and know-it-all with Yahoo! Mobile. Try it now.
