Overview: A one time dead zone off Oregon’s coast turns out not to be an isolated incident. Oxygen levels are plummeting every summer now. Scientists deploy an army of sensors, including a diving robot explorer, to learn what’s changed in our ocean. For the last 40 years salmon and steelhead have been missing from a place called Whychus creek. But they’re about to come back, and ecologists are getting busy with bulldozers as they prepare for their return. A trip to the Oregon Coast Aquarium for a look at what it takes staff and volunteers to care for thousands of animals.