Melting ice may have fed Earth's first oxygen swings
South African rocks examined in a peer-reviewed Nature Communications study suggest that phosphorus washed into the ocean after ancient glaciations may have boosted oxygen production, while recycling from sediments prolonged atmospheric swings. A genome-wide search across animal phyla also places envelope-carrying jumping genes before the Cambrian. Climate-linked oxygen swings and the pre-Cambrian origin of envelope-carrying retrotransposons point to a long history of early living conditions and genetic mobility.
Science··Evening
Post-glacial phosphorus accelerated oxygen production
A study in Nature Communications finds a marked phosphorus rise after ancient glaciations in rocks of South Africa's Transvaal Supergroup. Faster weathering after the ice retreated carried this nutrient, which limits marine productivity, into the ocean and strengthened oxygenation. Feedback between sulfate supply and the ocean's redox state then governed how much phosphorus sediments returned to the water. A biogeochemical model shows that this cycle could produce large swings in atmospheric oxygen, offering a mechanism for why the transition to a persistently oxygenated atmosphere did not finish in a single step.[1]
Envelope-carrying jumping genes reach back before the Cambrian
A peer-reviewed genomic search in eLife detected intact Ty3/gypsy retrotransposons carrying envelope genes in animal groups as old as cnidarians and ctenophores. Evolutionary trees built from conserved POL protein regions and predicted protein structures revealed two distinct envelope types. Because the envelope genes largely diverged alongside pol through evolutionary history, the authors interpret them as ancient acquisitions predating the Cambrian rather than pieces captured repeatedly in recent times. Near-identical copies in some host lineages also show that more recent expansions continued on top of that old origin.[2]
Oxygen swings stretched across hundreds of millions of years
The Great Oxidation Episode lasted from about 2.43 to 2.06 billion years ago and was marked by extreme climatic instability. A Leeds-led team tracked how phosphorus was distributed among mineral phases in rocks of South Africa's Transvaal Supergroup across the episode's final two glaciations. Faster weathering after each glaciation carried phosphorus into the ocean and supported oxygenation. Sulphate supply and ocean redox state then controlled how much phosphorus sediments returned to the water; modelling shows that this feedback could prolong large swings in atmospheric oxygen.[1]
