It is, in the jargon of the NOAA, an "unusual mortality event" (UME). The government-ese refers to the deaths of more than 260 bottlenose dolphins since February in states bordering the Gulf of Mexico. While stranding deaths occur every year, the numbers this year are three times higher than normal, reports AccuWeather. The dolphins are washing up in Louisiana, Mississippi, Alabama, and the panhandle of Florida, and researchers say it's too early to say what's going on. The UME designation, however, means that an investigative team is now on the case. In the meantime, two theories have emerged—that the dolphins are suffering from too much freshwater and lingering effects from the 2010 Deepwater Horizon spill.
Dolphins need salt water to survive, and they may not be getting enough along the coast in bays, sounds, and other waterways, explains the New Orleans Times-Picayune. One big reason is the year's heavy flooding—and the related opening of spillways and such—which has led to the Mississippi River running unusually high. The river feeds the waterways where the dolphins live, and some of the washed-up dolphins do indeed have lesions consistent with too much freshwater. Scientists also will investigate whether the 2010 spill could be a contributing factor. Dolphins that survived suffered lung and adrenal gland problems that might have made them more susceptible to water with low salinity, per USA Today. (In Canada, better news for dolphins and whales in the "Free Willy" act.)