Color-changing indicator predicts algal blooms

Murky green algal blooms are more than a major eyesore; they reveal that a body of water could be unsafe for swimming or drinking. Currently, however, there isn't an effective warning system for impending blooms. Now, researchers in ACS Applied Nano Materials report an indicator that changes color when exposed to rising levels of alkaline phosphatase—an enzyme that forecasts phytoplankton's exponential growth. This change can be detected by the naked eye or a smartphone.