A strange green organism has spread around the globe, clogging up the world's rivers It began with a few small strange patches of slime, clinging to the rocks of the Heber River in Canada. Within a year, the patches had become thick, blooming mats. Within a few years the mats had grown into a giant green snot. And within a few decades this snot had spread around the world, clogging up rivers as far away as South America, Europe and Australasia. This snot, which is still flourishing today, is caused by a microscopic alga, a diatom that goes by its...