Changes in plankton productivity have been connected with the end-Permian mass extinction. A box-model – proxy data comparison suggests that an increase of microbial sulfate reduction (MSR) can explain excursions in δ34SCAS and δ18OCAS. These fluctuations are contemporaneous with the biodiversity crisis and are probably related to enhanced availability of organic substrates. This caused MSR to increase proportionally and induce the observed positive δ18OCAS excursion. The scenario would only require an increase in the oceans organic carbon inventory – a suggestion that can be linked to the climate warming and elevated continental weathering at that time. These physical processes are linked to the short-term carbon cycle, as ocean fertilization by nutrient input stimulated primary productivity. Enhanced microbial activity can be regarded as the killing agent because of increased oxygen consumption (aerobic respiration) and H2S (MSR) production. This caused a rapid global expansion of euxinic water and resulted in iron limitation in the ocean water. This, together with decreased iron supply due to a change in fluviatile regimes, reduced pyrite burial, explaining a negative δ34SCAS excursion. This suggests that the latest Permian ocean was not dead (‘Strangelove Ocean’) but rather alive, and that microbial life can create adverse conditions for eukaryotic organisms.

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