'Dead zones' threaten fisheriesMay 27, 2004, Christian Science Monitor       http://www.csmonitor.com/2004/0527/p13s01-sten.html            By Mark Clayton | Staff writer of The Christian Science Monitor       In midsummer, the northern Gulf of Mexico, where the Mississippi River       empties into it, may shimmer like any other swath of sea. But a few score       feet below, bottom-dwelling fish and [...]