By 1986 massive blooms of cyanobacteria began occurring, as well as dense populations of roach, a fish that benefited from the pollution's mineral nutrients. Roach eat zooplankton that otherwise keep cyanobacteria in check.
By 1986, significant blooms of cyanobacteria emerged, accompanied by dense populations of roach, a species that thrived on the pollution's mineral content. Roach feed on zooplankton, which typically regulate the growth of cyanobacteria.