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The large increase of δ^(13)C_(carb)-depth gradient and the end-Permian mass extinction

Science China Earth Sciences 2012年第7期55卷 1101-1109页

作者： SONG HaiJun TONG JinNan XIONG YanLin SUN DongYing TIAN Li SONG HuYue State Key Laboratory of Biogeology and Environmental Geology China University of GeosciencesWuhan 430074China

Carbonate carbon isotope （δ^13Ccarb） has received considerable attention in the Permian-Triassic transition for its rapid negative shift coinciding with the great end-Permian mass extinction event. The mechanism has long been debated for such a c~ δ^13Ccarb negative excursion through the end-Permian crisis and subsequent large perturbations in the entire Early Triassic. A δ^13Ccarb depth gradient is observed at the Permian-Triassic boundary sections of different water-depths, i.e., the Yangou, Meishan, and Shangsi sections, and such a large δ^13Ccarb-depth gradient near the end-Permian mass extinction horizon is believed to result from a stratified Paleotethys Ocean with widespread anoxic/euxinic deep water. The evolution of δ^13Ccarb-depth gradient com- bined with paleontological and geochemical data suggests that abundant cyanobacteria and vigorous biological pump in the immediate aftermath of the end-Permian extinction would be the main cause of the large δ^13Ccarb-depth gradient, and the enhanced continental weathering with the mass extinction on land provides a mass amount of nutriment for the flourishing cyanobacteria. Photic zone anoxia/euxinia from the onset of chemocline upward excursion might be the direct cause for the mass extinction whereas the instability of chemocline in the stratified Early Triassic ocean would be the reason for the delayed and involuted biotic recovery.

关键词： Permian-Triassic boundary carbon isotope ocean stratification bioproductivity biological pump mass extinction

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Biogeochemistry of Lake Baikal Stony Littoral

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Journal of Geoscience and Environment Protection 2019年第10期7卷 72-79页

作者： Alexandr Nikolaevich Suturin Limnological Institute of the Siberian Branch of RAS Irkutsk Russia

The problem of biogenic income from rocks into a water ecosystem and of their use by hydrobionts is considered by the example of Lake Baikal biogeocenoses. A complex interreaction of stony material and Baikal water occurs on the stony littoral of Lake Baikal with an active participation of benthic and planktonic hydrobionts. Biogeochemical processes enable income of biophile elements providing productivity of stony littoral and hydrobionts biodiversity. A particular role in the littoral zone belongs to symbiotic organisms: lichens and sponges. They extract from the tocks a wide spectrum of macro- and micro- elements including phosphorus, fixe nitrogen and consume carbon. Biodiversity and bioproductivity of stony littoral depend on the diversity of petrographic composition of the rocks and on their geochemical peculiarities. Increase of anthropogenic impact onto the stony littoral manifested by income of biogenic elements and alien microbial cenosis flow results in degradation of primary aquatic biogeocenoses.

关键词： Stony Littoral Lake Baikal Biogeochemistry Hydrobionts Biodiversity bioproductivity Anthropogenic Pollution

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