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 Hey there, Earth enthusiast! Check my favorite Earth-friendly products: Bamboo toilet paper: https://shrsl.com/3cvku Bamboo paper towels: https://shrsl.com/3cvkw Compostable tableware: https://shrsl.com/3cvkz Compostable trash bags: https://shrsl.com/3cvl0 Bamboo cutlery + straw! : https://shrsl.com/3cwfl Eco-Friendly Tote (great for grocery shopping!): https://shrsl.com/3cwfp Reusable straws + cleaning brushes (my fav!): https://shrsl.com/3cwft Eco-friendly laundry detergent: https://shrsl.com/3cwgo Directly offset your carbon footprint with Wren: https://shrsl.com/3d0t2 (Just click link, press get started, take the free C footprint quiz, then choose how much you want to reduce your footprint by donating to the C sequestration projects they're funding!) Non-textbook books I recommend: Oxygen by D. Canfield: https://amzn.to/3gffbCL Brief history of Earth by A. Knoll: https://amzn.to/3w3hC1I Life on young planet by A. Knoll: https://amzn.to/2RBMpny Some assembly required by N. Shubin: https://amzn.to/3w1Ezm2 Your inner fish by N. Shubin: https://amzn.to/3cpw3Wb Oxygen by N. Lane: https://amzn.to/3z4FgwZ Alien Oceans by K. Hand: https://amzn.to/3clMx1l Life's Engines: https://amzn.to/3w1Nhke Tools I use as a geologist/teacher/student: Geology field notebook: https://amzn.to/3lb6dJf Geology rock hammer: https://amzn.to/3DZw8MA Geological compass: https://amzn.to/3hfbdLu Geological hand lens: https://amzn.to/3jXysM5 Camera: https://amzn.to/3l6fGRT Carbon-neutral pencil bag: https://shrsl.com/3cvjv Carbon-neutral backpack: https://shrsl.com/3cvkc Disclaimer: Links included in this description might be affiliate links. If you purchase a product or service with the links that I provide I may receive a small commission, but there is no additional charge to you! Thank you for supporting my channel so I can continue to provide you with free content each week! And as always, let me know your topic suggestions in the comments down below!
