After weeks of estimates, countless models and hundreds of boat excursions seeking hints of oil in Louisiana's marshes, a bleak picture began to emerge this week as the first signs of thick, dark oil from the Gulf of Mexico oil spill could be seen blanketing a patch of marsh grass near the mouth of the Mississippi River. At the eastern reaches of the delta, where Pass a Loutre meets open water, dark brown oil was covering an entire patch of cane grass on Wednesday. On the open water, a dark-brown tint could be seen on grasses just above the water's...