First life

Natural History, Sept, 1998 by John J. Lee

As a microbial ecologist with the Museum's Department of Invertebrates, I was assigned to collect samples of Earth's first microorganisms for the new Hall of Biodiversity. These are stromatolites, microbial communities that carpeted the shallow seafloor 3.5 billion years ago, generating enough oxygen over the next 2 billion years to create the atmosphere.

Composed of layers of different types of bacteria, stromatolites are still forming in a few sites; one of the best known is called Solar Lake, on the Sinai Peninsula at the head of the Gulf of Aqaba. A small, shallow basin (about 250 by 140 feet) in which a layer of brackish water overlies saline water, Solar Lake is formed by seepage from the Red Sea, only 90 feet away. The upper layer, which accumulates during winter rains, acts like a lens, focusing the sun's energy into the deeper layer and making it so hot that no "higher" form of life can survive there. Near the shore, the stromatolites lie matted on the lake floor, but toward the middle of the lake, the thick mat floats some two feet below the water's surface.

I remember with fondness my first trip to Solar Lake, about twenty years ago, with Yehuda Cohen of Hebrew University. He showed my daughter and me how to "walk on the waters"--that is, on the submerged stromatolite mats--of the lake. This is precarious, because if you stop, you sink. Only my daughter and Yehuda made it across. Later at the university, he pointed out a photograph of a long core from the lake, each of its layers representing one year--a record of life dating back 4,600 years. One could even discern the sandy layers that correlate with earthquake years.

This year I revisited the lake, armed with letters of permission from the Egyptian ambassador to the United Nations and various Egyptian government agencies. The project manager for the Gulf of Aqaba, Alain Jeudy de Grissac, showed me and other scientists where we could collect our samples without damaging the lake or disturbing the multinational experiments going on there, and he helped us extract two cores. He also explained that the soldiers we saw were there to protect the site from damage by tourists, who sometimes try to walk on the water (I had a twinge as I remembered our transgression of twenty years ago). The damage already done to the lake, he said, may take sixty years or more to repair. The Egyptian government plans to develop tourism in the Sinai, but we were assured that the Solar Lake habitat will be preserved for future generations.

I made the long trip back to New York with the stromatolite cores packed in a thirty-gallon cask on rollers. One of them is now on display in the Museum's new Hall of Biodiversity.

John J. Lee has been associated with the museum's department of invertebrates since 1957. He is a distinguished professor of biology at City College of New York. His most recent book is the second edition of The Illustrated Guide to the Protozoa. His daughter is now a microbial ecologist.