WOODS HOLE-Bruce Keafer calls it a robot in a box. Roughly the size of a kitchen sink, it was lowered into the waters off Portsmouth, N.H. last week, where it will sample marine organisms to measure toxic red tide cells over the next 45 days. The device, he hopes, will eventually be a tool for forecasting outbreaks of red tide. Initial results have detected red tide cells in areas where shellfish hadn’t previously tested positive for toxins. The sensor transmits information in real time to researchers about the genetic makeup of organisms in the water.