Because lakes are landlocked bodies of water, they are our planet's experimental mixing pots. They can stew strange chemistry and give rise to anomalous creatures found nowhere else on Earth.
http://www.mnn.com/earth-matters/wi...most-bizarre-lakes-in-the-world/lake-balkhash
http://www.mnn.com/earth-matters/wi...most-bizarre-lakes-in-the-world/lake-balkhash