 Below the top layer of oxygenated water, Lake Matano's depths are anoxic, free of sulfates, and rich in iron.These conditions make Lake Matano an analog for Earth's oceans during the Archean Eon, which is useful for studying relationships between anoxygenic phototrophs and banded iron formations.The lake contains a population of green sulfur bacteria that conducts photosynthesis with bacteriochlorophyll "e".