1) The area is large. But this is meaningless without knowledge of the density.
2) I can't find a reference, but a prof of marine biology was on the bbc a couple of days ago and apparently this oil spill doesn't even make it into the top 40 worst man-made disasters (e.g compare to bhopal, chernobyl, pacific gyre)
The Niger Delta sees this volume of oil spilled EVERY SINGLE YEAR and no-one gives a fuck. No-one is held to account, there's no press, there's no nothing. The culprits are all the major US/European oil firms.