Possible evolution of mobile animals in association with microbial mats

• Published in: Nature Geoscience
• Main Authors: Gingras, Murray, Hagadorn, James, Seilacher, Adolf, Lalonde, Stefan V., Pecoits, Ernesto, Petrash, Daniel, Konhauser, Kurt
• Other Authors: Department of Earth and Atmospheric Sciences Edmonton, University of Alberta, Department of Earth Sciences Denver, Denver Museum of Nature and Science, Department of Geology and Geophysics, Yale University New Haven, Domaines Océaniques (LDO), Centre National de la Recherche Scientifique (CNRS)-Institut d'écologie et environnement-Observatoire des Sciences de l'Univers-Université de Brest (UBO)-Institut national des sciences de l'Univers (INSU - CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2011
• Subjects: TRACE FOSSIL RECORD; CAMBRIAN TRANSITION; EDIACARA-BIOTA; WHITE SEA; SULFUR; RUSSIA; OXYGEN; LIFE; RISE; [SDE]Environmental Sciences; [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry; [SDE.MCG]Environmental Sciences/Global Changes; Burrows; White Sea
• Online Access: https://hal-insu.archives-ouvertes.fr/insu-00808481; https://doi.org/10.1038/NGEO1142

International audience Complex animals first evolved during the Ediacaran period, between 635 and 542 million years ago, when the oceans were just becoming fully oxygenated. In situ fossils of the mobile forms of these animals are associated with microbial sedimentary structures(1-3), and the animal's trace fossils generally were formed parallel to the surface of the seabed, at or below the sediment-water interface(4,5). This evidence suggests the earliest mobile animals inhabited settings with high microbial populations, and may have mined microbially bound sediments for food resources(6-8). Here we report the association of mobile animals-insect larvae, oligochaetes and burrowing shore crabs-with microbial mats in a modern hypersaline lagoon in Venezuela. The lagoon is characterized by low concentrations of dissolved O-2 and pervasive biomats dominated by oxygen-producing cyanobacteria, both analogous to conditions during the Ediacaran. We find that, during the day, O-2 levels in the biomats are four times higher than in the overlying water column. We therefore conclude that the animals harvest both food and O-2 from the biomats. In doing so, the animals produce horizontal burrows similar to those found in Ediacaran-aged rocks. We suggest that early mobile animals may have evolved in similar environments during the Ediacaran, effectively exploiting oases rich in O-2 that formed within low oxygen settings.