The Messel Lake in the Eocene
The tropical climate conditions favored the rapid development of a vegetation cover: shrubs, vines, trees and ferns surrounded the lake and stabilized the crater’s rim with their roots. Algae and a carpet of aquatic plants gave the water a dark green to brownish color, and animals began to populate the newly formed habitat as well. In this process, the upper layers of the lake were clearly favored, since they alone offered sufficient heat and particularly oxygen for the majority of living organisms. The calm and dark bottom was untouched by currents and only housed highly specialized bacteria that do not require oxygen for their survival and feed of the sunken remains of dead animals. The high number of fossilized birds and bats, which hunted close to or above the water and later were submerged in the lake, suggests that toxic gases may have risen from the water’s surface.