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.
Pencemaran berasal dari industri, pertanian, dan limbah; dan sebuah danau mungkin telah rusak parah meskipun masih tampak jernih, kata Cosgrove, yang menambahkan, ” Lalu, terjadi sesuatu ​ — misalnya perubahan suhu air ​ — dan mendadak sebuah danau dapat berubah total.