Life in Oxic, Suboxic, & Anoxic Sediments (Yes, Some Life Doesn't Require Oxygen!) | GEO GIRL

Life doesn't stop below Earth's surface! Microbes in sediment and soil create natural zones based on their distinct metabolic needs. This video covers the depth and processes of the oxic, suboxic, and anoxic zones of sediment.
Aerobic microbes live in the oxic zone of sediment at the top of the sediment water interface. Therefore, aerobes are the first to tackle organic matter degradation. Aerobic microbes are responsible for the majority of organic matter decomposition in pelagic and coastal marine environments because they have the most energetically favorable metabolism. The oxic zone can either be very shallow or penetrate deep in the sediment depending on sedimentation rate, organic carbon reactivity, oxygen concentrations in the water column, porosity & permeability of sediment, and oxygen consumption by porewater reductants. The suboxic zone of sediment is dominated by nitrogen, manganese, and iron metabolizing microbes, which are typically anaerobic microbes (life without oxygen is more comment than you think). While many of the metabolic pathways below the oxic zone still use organic carbon as a reductant, the organic material is becoming less reactive deeper into the sediment because the labile organic matter was decomposed by the aerobic microbes. The anoxic zone is dominated by sulfate reducing bacteria (and other sulfur cycling organisms), and below the sulfate reduction zone is the methanogenesis zone. Sulfate reducing bacteria play a major role in organic matter degradation in coastal marine settings where sulfate is abundant, but they play a very minor to negligible role in pelagic and freshwater sediments where sulfate concentrations are much lower. The methane zone is dominated by methanogens and methanotrophs, which produce and consume methane, respectively. Melting methane hydrates is of great concern due to the current global warming trend, so studying methanotrophs for their C sink capabilities is more important than ever.

References: Geomicrobiology: https://amzn.to/2WAloTR
Biology of Microorganisms: https://amzn.to/3kQqIuD

GEO GIRL Website: https://www.geogirlscience.com/ (visit my website to see all my courses, shop merch, learn more about me, and donate to support the channel if you'd like!)

0:00 microbial zonation
0:53 what does oxic, suboxic, & anoxic mean?
3:00 oxic zone organisms
6:51 how deep does the oxic zone penetrate?
10:39 N cycle in suboxic sediment
14:44 Mn cycle in suboxic sediment
17:49 Fe cycle in suboxic sediment
19:03 S cycle in anoxic sediment
25:01 CH4 cycle in anoxic sediment
27:59 upcoming videos & references

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Oxygen by D. Canfield: https://amzn.to/3gffbCL
Brief history of Earth by A. Knoll: https://amzn.to/3w3hC1I
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