Without long term trend data these assertions are totally useless. On the east coast we have red tide which creates problems for the clam flats. These evidently have been known for eons. I would check this story out with some long time fishermen in the area - especially those who are not likely to look for a Government bail out.
I'd look at the hot underwater vents just off the coast...may be the exit flows have increased, became more toxic, hotter?