On May 2, 1878, George Francis of Adelaide, Australia, published the Þrst scholarly description of the potentially lethal eÝects produced by cyanobacteriaNthe microorganisms sometimes called blue-green algae or, more colloquially, pond scum. In a letter to Nature he noted that an alga he thought to be Nodularia spumigena had so proliferated in the estuary of the Murray River that it had formed a Othick scum like green oil paint, some two to six inches thick, and as thick and pasty as porridge.O This growth had rendered the water OunwholesomeO for cattle and other animals that drink at the surface, bringing on a rapid and sometimes terrible death: