Not far beneath the ocean’s surface, tiny phytoplankton swimming upward in a daily commute toward morning light sometimes encounter the watery equivalent of Rod Serling’s Twilight Zone: a sharp variation in marine currents that traps billions of these single-celled organisms and sends them tumbling head over heels until a shift in wind or tide alters the currents and sets them free. Scientists are aware of these thin layers of single-celled creatures and their enormous ecological ramifications, but until now, they knew little about the mechanisms responsible for their formation. The explanation by researchers in MIT’s Department of Civil and Environmental Engineering of how these common, startlingly dense layers of photosynthetic phytoplankton form, moves the scientific community a step closer to being able to predict harmful algal blooms, a well-known example of which is red tide. The work also opens new perspectives on other phenomena, like predatory feeding by larger organisms at these ecological hotspots. Read more.