I suppose that because phytoplankton is such an important food source in the oceans, that they'd want to monitor the blooms. Thus we could get warnings about crashes in the oceanic food chain, and panic. That, or the US is sure that Osama bin Laden is hiding in a phytoplankton bloom, and is recruiting disaffected marine mammals to his cause.
Unfortunately, the Aqua photo wasn't showing when I came to this thread. I suppose I'll have to check on NASA's website for it.
...(later)... Ooh, pretty swirlies. Here's a link for more Aqua images of NZ:
http://visibleearth.nasa.gov/view_se...ategoryID=2234