The Monterey Bay endured decades of overfishing and pollution; it was one of the most polluted places along the California coast. Today, the Bay hosts a thriving wealth of humpback and blue whales, elephant seals, sea otters and more. We’ll talk to experts about the history of conservation in the Bay, as well as ongoing opportunities and threats to that ecosystem. PBS and the BBC present “Big Blue Live,” a three-night live broadcast airing tonight on KQED 9 at 8 p.m. through this Wednesday Sept. 2.