Antarctic microbial mats: A modern analog for Archean lacustrine oxygen oases

Abstract

The evolution of oxygenic photosynthesis was the most important geochemical event in Earth history, causing the Great Oxidation Event (GOE) ~2.4 b.y. ago. However, evidence is mixed as to whether O 2 production occurred locally as much as 2.8 b.y. ago, creating O 2 oases, or initiated just prior to the GOE. The biogeochemical dynamics of possible O 2 oases have been poorly constrained due to the absence of modern analogs. However, cyanobacteria in microbial mats in a perennially anoxic region of Lake Fryxell, Antarctica, create a 1-2 mm O 2 -containing layer in the upper mat during summer, providing the first known modern analog for formation of benthic O 2 oases. In Lake Fryxell, benthic cyanobacteria are present below the oxycline in the lake. Mat photosynthesis rates were slow due to low photon flux rate (1-2 µmol m -2 s -1) under thick ice cover, but photosynthetic O 2 production was sufficient to sustain up to 50 µmol O 2 L -1

Microbial Mat Communities along an Oxygen Gradient in a Perennially Ice-Covered Antarctic Lake

“…Sumner et al (28) showed that oxygen penetrates at least 17 mm into the pinnacle mats during the austral summer. In addition, prostrate mats from below the water column oxygen limit contain some oxygen in the upper millimeters, which is likely produced locally by the P. pseudopriestleyi-dominated cyanobacterial community.…”

“…As part of the description of the mat communities in Lake Fryxell, we identified a highly abundant cyanobacterium that occupies a unique niche below the oxycline where it produces an oxygenated "oasis" (28), and we therefore undertook a comprehensive phylogenetic analysis of this organism.…”

Iron formations: A global record of Neoarchaean to Palaeoproterozoic environmental history

“…Under such a scenario, oxygen produced by the benthic microbial community would be consumed proximal to the mat, much as is observed in some modern mat systems (e.g., Gingras et al, 2011;Sumner et al, 2015).…”

Very Complex Matter: Collaborations in Art and Geobiology

“…16. Sumner et al (2015 In the performance, which was presented publically in workshop form in 2015, and will be presented in final form by the Donna Sternberg Dancers in Los Angeles in spring, 2018, the audience sees colourful, projected fragments of story drawings arising from the floor. They swirl in a vortex towards the sky as a slightly ominous soundscape establishes the emotional tone.…”