[Rhodes22-list] Expanding Dead Zone in the Gulf of Mexico - some ideas

[Jim White]

Dave:
  I found this paper regarding the GOM Dead Zone. It is pretty accurate, and describes the "capping" by fresh water better than I can.....I always was a lousy teacher, that's why I stuck to science!
   
  http://www.ncseonline.org/NLE/CRSreports/06Oct/98-869.pdf
   
  Marine Protists, which include the red tide organism(s) are considered part of the plankton. By definition, they are somewhat motile within a specific area, but are unable to effectively move against current transport. Dinoflagellate orientation (i.e. their spatial location) varies according to a number of factors, including diurnal cycles (http://www.int-res.com/articles/meps/167/m167p105.pdf). These critters have a morphology (shape) that allows them to somewhat "swim" by the use of a single tail, or flagella. Blooms are an interesting phenomenon, and one theory suggests that it is changes in the life cycle (not necessarily reproduction, but rather an encystment phase) that may be a significant contributing factor (http://www.springerlink.com/content/p058758t8779213h/). 
   
  Ain't Google Scholar great? In the old days I used to have to go to the University (or at least the online library) to amass citations whenever I wrote a report or a paper. Now I can just Google it....
   
  BTW, the red tide organism(s) belong to Kingdom Protista,  Phylum Dinoflagellata. This Kingdom also includes algaes, diatoms, protozoans, amoebas and a lot of other wierd and interesting biota.....just FYI for all you taxonimist types out there :-)
   
  Cheers
   
  jw
   
  

DCLewis1 at aol.com wrote:
  
Robert,

I think I'm learning they don't know what's causing the Red Tide - JW please 
correct me if I'm wrong.

JW knows a gazillion times more about this than I do, but I'd assumed algae 
(Red Tide) reproduced asexually, in which case no explicit action individually 
or in swarms is necessary, nor is communications between sexes or anything 
else needed. They just reproduce, if they are in a hospitable environment. 

Having said that, I just did a quick Google and discovered algae reproduce 
sexually and asexually. If they reproduce sexually, group behavior (swarms) 
might matter.

JW, any info regarding Red Tide algae reproductive behavior? If it is 
sexual, can algae really move enough to swarm? I'd always thought they just 
floated along wherever they were, as opposed to purposefully swimming to or away 
from some object at some reasonable distance, say a cm.

The ability of algae to swarm might have some practical import. For example, 
there you were floating placidly on the bay when out of nowhere assembles a 
humongeous mass of algae - attracted perhaps by the shape of the keel of your 
R22. You need to be prepared.

I'm really interested in the oxygen problem, though. If fresh water carries 
more oxygen than salt water, then it seems to me that every depth in a salt 
water/fresh water overlay should have as much oxygen, or more, than an 
equivalent salt water depth. I don't understand the barrier that makes it less - 
provided that the primary oxygen source is at the air/water interface and the 
fresh water is oxygenated to begin with. IF the primary source of oxygen in 
the water is what is in the salt water to start with (i.e. little diffusion 
of oxygen into the water at the air/water interface), and if the fresh water 
is oxygen deficient, then I can see how the fresh water would absorb oxygen 
from the salt water, and deplete the oxygen in the salt water. Why would 
there be limited diffusion of oxygen into the water from the air/water interface? 
Pollution (oil films)? Curious.

Dave



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