http://biopact.com/2007/03/harvesting-algae-blooms-from-ocean.html

Something I have talked about for awhile, capturing algae from the ocean, rivers, and lakes to get energy and remove fertilizer and manure runoff from the water. 

This is an ethanol company, but I prefer biodiesel and biogas production with the residue from making the biodiesel.  It also yields organic fertlizer, as well as preventing fertilizer run off from releasing methane from sediments.  Cutting down a huge GHG source.

The biogas could be used as backup power for renewables, used in fuel cell/turbines at 75% efficiency.  Floating biodigestors that collect and separate the biodiesel and process the rest into biogas.  Powered by wind, wave, and solar power.  The biogas sent ashore to fuel cell power stations. 

The CO2 from the fuel cells sent back into solar collector algae systems that use it to enhance the growth of the algae.  Then the cycle continues.