Hypoxia, low levels of oxygen, plague coastal waters, including Long Island Sound, every summer. These “dead zones” can force fish and invertebrates to scatter, and make others susceptible to disease. When concentrations are extremely low fish and shellfish unable to flee may die. The video, created by the NOAA Environmental Visualization Lab, describes how high levels of nutrients lead to hypoxia. The setting is the Gulf of Mexico, but much of what is discussed applies to the Sound. The video was produced with support from the Smithsonian Institution, Dalhousie University, and Texas A&M.