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Biological Sciences Mercury isotope signatures record photic zone euxinia in the Mesoproterozoic ocean

Abstract.

"Photic zone euxinia (PZE) is a condition where anoxic, H2S-rich waters occur in the photic zone (PZ). PZE has been invoked as an impediment to the evolution of complex life on early Earth and as a kill mechanism for Phanerozoic mass extinctions. Here, we investigate the potential application of mercury (Hg) stable isotopes in marine sedimentary rocks as a proxy for PZE by measuring Hg isotope compositions in late Mesoproterozoic (∼1.1 Ga) shales that have independent evidence of PZE during discrete intervals. [...]"

Source: PNAS
Authors: Wang Zheng et al.
DOI: 10.1073/pnas.1721733115

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Big Storms Pump Mediterranean Water Far into the Black Sea

"For the first time, scientists provide a sea-wide view of what happens to Mediterranean waters that flow into the Black Sea through the Bosporus Strait.

Below a depth of about 150 meters, the Black Sea is devoid of oxygen. Only certain microbes can survive in this “dead zone,” which reaches depths of over 2000 meters. Warm, salty water flowing from the Mediterranean Sea into the Black Sea ventilates the middepth water column of the sea, trapping anoxic water below and maintaining the sea’s distinctive structure. However, the precise fate of inflowing Mediterranean waters has remained something of a mystery to scientists. [...]"

Source: EOS
Author: Sarah Stanley

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