Marine animals inevitably eat what we toss in the ocean, including pervasive plastics – but how much is too much? The bar is low, according to a new study out Monday: less than three sugar cubes' worth could kill birds like Atlantic puffins, for example. That threshold "is much smaller than we expected," said Erin Murphy, ocean plastics researcher at the Ocean Conservancy , the nonprofit behind the study. The paper published by The Proceedings of the National Academy of Sciences saw researchers