In a year where we’ve already seen unusual numbers of dead dolphins and toxic algae blooms in the Great Lakes, it feels like it was only a matter of time before the two combined in a major bummer of mammalian death. And lo, 2013 just broke the record for manatee fatalities in Florida.Biologists have said that toxic algae blooms in the Gulf of Mexico have deprived the water of oxygen, leading to the death of 769 manatees through October 29. This blows past the previous record of 766, set in 2010, with two months left to go.“With 2013's catastrophic loss of manatee lives coming so close on the heels of the mass mortality suffered during 2010, the already difficult job to ensure the survival of these gentle and defenseless marine mammals has been made all the more challenging,” according to a press release from Save the Manatee Club’s Patrick Rose. “We must demand better stewardship of our waters and waterways.”The largest dead zones in the Gulf of Mexico are caused by “excessive nutrient pollution,” caused by fertilizer run-off. As Motherboard’s Brian Merchant explained, the fertilizer run-off makes its way to the Gulf via the Mississippi River, where, upon arrival, “All those nutrients cause massive algae feeding-frenzies that suck up all of the available oxygen, creating what scientists call "hypoxic" (very low oxygen) and "anoxic" (no oxygen) zones. Dead zones.”According to Phys.Org, a toxic red-tide bloom killed 276 manatees this winter and spring in southwestern Florida. There has also been an unusually high number of dead manatee calves—123 stillborn, newborn or young calf deaths.