Possible solution to oxygen dead zones in the ocean....?!

For background info on oxygen dead zones in the ocean,  please read :

http://en.wikipedia.org/wiki/Dead_zone_%28ecology%29

These exist off the coast of california, florida and the east coast, and perhaps most notably to north america, at the exit of the mississipi river into the gulf of mexico.

In 2003 there were 146 dead zones known in the ocean.   Fish going into them soon become unconscious and die.   Sea life does not exist there at the bottom or in the water column.  The shell fish have all croaked there. The largest at that time was 30000 square km.

In 2008 there were about 405 dead zones.  the largest at that time last year was about 70000 square km.

These are usually caused by fertilizer (ammonium nitrate,potassium and phosphorus)  in rain water run off from farmers fields getting into the rivers and emptying out into the oceans.  Dead zones occur in rivers as well.

This causes algae to grow,  which, since it is a carpet at the surface,  prevents atmospheric oxygen (O2) from entering the water column by diffusion.  It is a careful balance, because it gives off O2 and absorbs CO2 during the day by photosynthesis, and absorbs O2 and gives off CO2 during respiration at night.  It slightly gives off more O2 than it makes, but because it blocks diffusion, it suffocates the ocean.

As algae decomposes in the ocean and rivers by bacteria,  it gives off plenty of CO2 and absorbs O2 from the water column and the atmosphere.   This creates the dead zone.

Remember the Tom Hanks movie , Forest Gump,  where he starts a shrimp fishing business in that area?

If a fleet of such ships could be converted to harvest algae while its young before it decomposes before the end of its life cycle annually,  it could be converted to organic fertilizer for farmers fields, or better yet, into biodiesel or food stuffs for herd animals.  It would be a profitable venture, and would prevent the dead zone from becoming more severe than it might otherwise be.

This takes a change in mind set and creates a whole new market.  Not a trivial task.

We need alternatives to classical farming fertilizers,   or need to curb there use in ground water run off areas or areas prone to flooding.  But the farmers are cynical about this and see the end of their livelihoods if fertilers stop altogether, and also see possible starvation of many people if we stop using them.

This is still a difficult problem,  but harvesting of algae could be a proactive step in helping to alleviate the dead zone problem.