Contamination comes from industry, farms, and sewage; and serious damage may already have occurred to a lake even though it looks pristine, Cosgrove said, adding: “Then something happens ​ — like a change in water temperature — ​ and all of a sudden a lake can be completely transformed.
Kosgrovs. Viņš turpināja: ” Tad kaut kas notiek, piemēram, mainās ūdens temperatūra, un ezers pēkšņi pilnīgi pārveidojas.