Can coastal "dead zones" produce the next alternative fuel?

Since the 1960’s, the number of ocean "dead zones" has doubled every 10 years. As a lot of the ocean's sea life lives in coastal areas, this doesn't bode well for marine life.

But does this spell an opportunity for harvesting the next alternative energy source? In part, these dead zones are a result of nitrogen rich agricultural run-off, which feeds and makes phytoplankton proliferate, and ultimately die and sink to the bottom as organic matter. Could this massive amount of organic matter be harvested and converted into a viable bio-fuel source?

Mankind is essentially fertilizing the coastal waters. Not that this is a good thing, but could we take advantage of a bad situation by "farming" the resultant organic matter?

Disclosure: no positions