The oldest evidence of bioturbation on Earth

The Ediacaran Period, an interval in Earth's history after the Snowball Earth glaciations but before the Cambrian radiations, marks the introduction of complex macroscopic organisms synchronously in unrelated groups. It has been proposed that the increase in size in marine organisms was triggered by the oxygenation of Ediacaran oceans.  

An Ediacaran trace fossil, made when an organism burrowed below a microbial mat [Credit: Wikimedia Commons]

New research shows that animals, rather than a late Neoproterozoic increase in oxygen concentration, could equally lead to a revolution in the structure and evolution of marine paleocommunities. 

In the course of studying Ediacaran-age rocks in a remote region of arctic Siberia, Vladimir Rogov and fellow researchers from Institute of Petroleum Geology and Geophysics in Novosibirsk (Russia) unexpectedly came across the oldest evidence of bioturbation (disruption of fine-laminated sediments by purposeful burrowing of animals in search for food) that significantly precedes the Cambrian radiations. 

Of special interest is that the advent of bioturbation in the fossil record coincides with the earliest ecological differentiation of macroscopic Ediacaran communities, which is interpreted to be a direct consequence of ecosystem engineering by animals. 

Bioturbation in modern seafloor habitats substantially affects key ecosystem process, including biogeochemical interactions, nutrient cycling, and primary productivity; the first appearance and expansion of bioturbation in the Ediacaran, therefore, must have had a profound effect on ecosystem structure and functioning. 

Source: Geological Society of America [March 20, 2012]