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

[DCLewis1 at aol.com]

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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