I saw reports earlier that an oil slick had been spotted during the search for MH370. It's interesting to compare the image of it on the BBC website (and elsewhere) to images of Trichodesmium (aka "Sea Sawdust") because to my untrained eye they look remarkably similar which makes me think the "oil slick" is a false alarm
I'd suggest the "oil" is the lighter grey streaks on the top right corner of the BBC picture and NOT the yellow stuff in the middle. It's just a poorly centred photo.