They dominated life on Earth when the planet was young

Sep 18, 2009 06:30 GMT  ·  By

Several billions of years ago, just after the first forms of life occurred, the world's shallow waters were dominated by stromatolites, layered accretionary structures made up of microorganism biofilms, especially by blue-green algae (cyanobacteria). These photosynthetic organisms and calcareous concretions generated dome-like lumps, which were for a long time the most advanced forms of life here on Earth. In an amazing, new find, geologists in Argentina have recently discovered stromatolites that are undergoing a forming process today, in very salty lakes high up in the Andes mountains.

According to Nature News, it may be that the conditions in which these formations grow are very similar to the primordial conditions on the planet, which means that experts may be able to gain new insight into the chain of events that eventually led to the development of more complex life. Scientists could also better understand the geochemical cycles that the earliest forms of life underwent, and precisely what triggered them into evolving into something more than mere lumps. Right now, there are few places where living stromatolites can be found. The Australian Shark Bay is one such location.

The team of investigators, led by National Scientific and Technical Research Council (CONICET-PROIMI) microbiologist Maria Eugenia Farias, encountered the living Andean stromatolites this year, in two expeditions it underwent, in February and August. The lakes in which the discoveries were made, known as the Socompa and Tolar Grande lagoons, were not very likely to yield such finds, because they were closed systems at a very high altitude.

Farias says that the environment in the lakes may be very similar to the one in which the stromatolites first appeared and developed. Salt concentrations in the waters are above 165 parts per million, and the amount of ultraviolet (UV) radiation on the locations can be 165 percent that recorded at sea level. High levels of nitrates mean that the stromatolites have no competition for food, and can therefore thrive. With a pH of 8.5, the Socompa lagoon lumps contain mostly cyanobacteria and diatoms, the team reveals.