The green snot taking over 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 scientific name Didymosphenia geminata. It has become so notorious it has its own moniker, Didymo. People have been blamed for the sudden, global explosion of this tiny organism, unwittingly carrying the algae from river to river on fishing gear, boats and kayaks. The huge snots it forms have wreaked havoc in waterways, forcing governments and environmental organisations to initiate huge and costly clean-up operations. But underlying the snots’ strange appearance is an even stranger story. About Didymo itself, about what it is, and how it behaves...more