Comments on: Demystifying gulf hypoxia, the “dead zone” http://lacoastpost.com/blog/?p=6170 Fri, 03 Sep 2010 21:11:19 +0000 hourly 1 http://wordpress.org/?v=3.0 By: Guest post on gulf hypoxia (GH) | lacoastpost.com http://lacoastpost.com/blog/?p=6170&cpage=1#comment-3437 Guest post on gulf hypoxia (GH) | lacoastpost.com Tue, 28 Apr 2009 23:54:55 +0000 http://lacoastpost.com/blog/?p=6170#comment-3437 [...] earlier posting on this website (April 9, 2009) discussed two recent papers on hypoxia in the Gulf and the infamous “dead zone,” one by Don [...] [...] earlier posting on this website (April 9, 2009) discussed two recent papers on hypoxia in the Gulf and the infamous “dead zone,” one by Don [...]

Like or Dislike: Thumb up 0 Thumb down 0

]]> By: Len http://lacoastpost.com/blog/?p=6170&cpage=1#comment-2828 Len Fri, 10 Apr 2009 00:40:51 +0000 http://lacoastpost.com/blog/?p=6170#comment-2828 Heidihoe- Dead zone is a hyperbolic phrase for hypoxic zone, arbitrarily defined as an area of a water body (in our case the continental shelf) within which, at a specific time during the summer, the bottom meter or so of the water column contains <2.5 parts per million of dissolved oxygen. Such a zone obviously isn't completely dead, just like a dog squashed by a truck at least for a time remains colonized by living bacteria. The area of the hypoxic zone can be described by any two dimensional system you like - acres, square miles, square kilometers, etc. In terms of time scale, although gulf hypoxia is measured during July and August it is thought to become established by June or so and last until October or so. Hurricanes can flush out hypoxia. In terms of "landloss," I don't like the term myself. I think in terms of newly inundated landscape, or the rate at which emergent coastal landscape becomes submergent or permanently flooded as the sea level rises and the coast subsides. Erosion is something else, where a shoreline retreats due to wave energy or scour or floating marshes are physically swept away by hurricanes. In either case plants and detritus in newly flooded or physically dislodged organic soils become available to decomposition by bacteria and fungi and can serve as the carbon source that is "burned" in respiration, resulting in the depletion of dissolved oxygen from the water column causing hypoxia. Heidihoe-
Dead zone is a hyperbolic phrase for hypoxic zone, arbitrarily defined as an area of a water body (in our case the continental shelf) within which, at a specific time during the summer, the bottom meter or so of the water column contains <2.5 parts per million of dissolved oxygen. Such a zone obviously isn't completely dead, just like a dog squashed by a truck at least for a time remains colonized by living bacteria.
The area of the hypoxic zone can be described by any two dimensional system you like – acres, square miles, square kilometers, etc.
In terms of time scale, although gulf hypoxia is measured during July and August it is thought to become established by June or so and last until October or so. Hurricanes can flush out hypoxia.
In terms of "landloss," I don't like the term myself. I think in terms of newly inundated landscape, or the rate at which emergent coastal landscape becomes submergent or permanently flooded as the sea level rises and the coast subsides. Erosion is something else, where a shoreline retreats due to wave energy or scour or floating marshes are physically swept away by hurricanes.
In either case plants and detritus in newly flooded or physically dislodged organic soils become available to decomposition by bacteria and fungi and can serve as the carbon source that is "burned" in respiration, resulting in the depletion of dissolved oxygen from the water column causing hypoxia.

Like or Dislike: Thumb up 0 Thumb down 0

]]> By: HeidiHoe http://lacoastpost.com/blog/?p=6170&cpage=1#comment-2805 HeidiHoe Thu, 09 Apr 2009 16:31:51 +0000 http://lacoastpost.com/blog/?p=6170#comment-2805 What is the "definition" of "dead" with respect to the "dead zone?" What "linear scale" is this definition applied on?? Kilometers, meters, etc. Also what "time scale?" years, months, days, hours, etc To me the scale questions are not trivial. Using an inappropriate scale could perhaps lead to inappropriate conclusions. Is coastal land really being "lost" or is its location merely being shifted around with changing water surface elevations??? What is the "definition" of "dead" with respect to the "dead zone?"

What "linear scale" is this definition applied on?? Kilometers, meters, etc.

Also what "time scale?" years, months, days, hours, etc

To me the scale questions are not trivial. Using an inappropriate scale could perhaps lead to inappropriate conclusions.

Is coastal land really being "lost" or is its location merely being shifted around with changing water surface elevations???

Like or Dislike: Thumb up 0 Thumb down 0

]]>