Slide 1Slide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Temperature and Salinity along the BosporusSlide 19Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25Slide 26Slide 27Slide 28Slide 29Slide 30Slide 31Slide 32Slide 33Slide 34Slide 35Slide 36Slide 37Slide 38Conclusions ISlide 40Slide 41Slide 42Anammox take-homes:Slide 44Denitrification take-homes:Slide 46Slide 47Slide 48Slide 49Slide 50Slide 51Slide 52Lecture 18 Redox Environments in the OceansDiagenesis in SedimentsAnoxic BasinsGlobal Carbon Cycle – Fate of organic matter in sedimentsRedox Half Reactions written as reductantsin terms of 1 e-Organic Matter Degradation (using Redfield stoichiometry)“OM” = (CH2O)106(NH3)16(H3PO4)Photosynthesis106CO2 + 16 NO3- + HPO42- + 18H+ 122 H2O → “OM” + 138 O2RespirationAerobic Respiration138 O2 + “OM” + 18 HCO3- → 124 CO2 + 16 NO3- + HPO42- + 140 H2ODenitrification94.4 NO3- + “OM” → 13.6 CO2 + 92.4 HCO3- + 55.3 N2 + 84.8 H2O + HPO42-Manganese Oxide Reduction236 MnO2 + “OM” + 364 CO2 + 104 H2O → 470 HCO3- + 8N2 + 236 Mn2+ + HPO42-Iron Oxide Reduction212 Fe2O3 + “OM” + 742 CO2 + 318 H2O → 848 HCO3- + 16 NH3 + 424 Fe2+ + HPO42-Sulfate Reduction53 SO42- + “OM” → 39 CO2 + 67 HCO3- + 16 NH4+ + 53 HS- + 39 H2O + HPO42-Methane Fermentation“OM” → 53 CO2 + 53 CH4 + 16 NH3 + HPO42- + 2H+Indicator species are circledDrilling Platform Blowout 2010 in the Deep Gulf of Mexico.J D Kessler et al. Science 2011;331:312-315The integrated dissolved oxygen anomaly was about3.0 x 1010 moles O2. If this O2 anomaly was due to CH4 oxidation, how much CH4 would it account for?Sampling stationsContours of O2 anomaly¼ O2(g) + H+ + e- = ½ H2O log K = 20.751/8 CO2(g) + H+ + e- = 1/8 CH4 (g) + ¼ H2O log K = 2.87Reverse 2nd reaction1/8 CH4(g) + 1/4H2O = 1/8 CO2(g) + H+ + e- log K = -2.87Add to first reaction1/4O2(g) + 1/8 CH4(g) = 1/8 CO2(g) + ¼ H2O log K = 17.88Multiply by x82O2(g) + CH4(g) = CO2(g) + 2 H2O log K = 143.04So: 3.0 x 1010 mol O2 = 1.5 x 1010 mol CH4 (upper limit due to C2H6, C3H8)Multi-colored sediments!What’s going on here???Rarely see all reactions easily at the same siteAerobic Respiration in Red Clay SedimentsDenitrification and MnO2 reduction – Hemipelagic SedimentsEmerson et al (1980)Guatemala Basin, North PacificIron reduction – Hemipelagic SedimentsEmerson et al (1980)East Pacific Rise – North PacificSulfate ReductionMethane ProductionAnaerobic Methane ConsumptionSaanich Inlet, BC SedimentsKuivila and Murray (1990)The Black Sea - IstanbulRush hour on the BosphorusRumelihisarıWhy is the Black Sea Interesting to Oceanographers?1. The classic anoxic basin.Oxic layer over sulfidic layer.2.Model for modern and ancient anoxic environments.3. Well developed transitionor suboxic zone. Model forworld’s organic rich sediments.4. Suboxic reactions easy to study here because of predictable depth locations.5. An ideal location to study effect of climate forcing on ocean distributions.Climate  Physical  Chemical  BiologicalThe Bosporus Strait connects the Black Sea with the Marmara Seaand is the only source of (relatively warm) salty water.Marmara SeaBlack SeaTemperature and Salinity along the BosporusGregg et al (1999)CILMEDN. SillS. SillBosporus Inflow and Entrainment of CILresults in the Bosporus Plume CIL (~50m)(from the surfacein winter)from Ozsoy et al.(1993)Bosporus InflowAvg CIL/BI ≈ 4 to 10The Suboxic Zone: Oxygen – Sulfide Depth versus DensityTotal depth = 2200mRegional coupling of sources and sinks (Deutsch et al, 2007; Capone and Knapp, 2007)Potential for such coupling exists in the Black SeaExample of NO3-, NO2- and NH4+ for R/V Knorr 2003 suboxic zoneCILData suggests anammoxFirst seen during 1988 Expedition0 1 0 0 2 0 0 3 0 0 4 0 0O x y g e n (M )1 71 6 . 51 61 5 . 51 51 4 . 51 41 3 . 5S i g m a T h e t a0 1 0 2 0 3 0 4 0 5 0H y d r o g e n S u l f i d e (M )S t . 7 L e g 8 K n o r r 2 0 0 3O x y g e nH y d r o g e n S u l f i d e0 1 2 3 4 5N O3- M1 71 6 . 51 61 5 . 51 51 4 . 51 41 3 . 5S i g m a T h e t a0 5 1 0 1 5 2 0 2 5N H4+ M0 0 . 0 2 0 . 0 4 0 . 0 6 0 . 0 8 0 . 1N O2- MS t 7 L e g 8 K n o r r 2 0 0 3N i t r a t eA m m o n i aN i t r i t eA combined geochemical and microbiological research approach consists of four approaches.1) Determine net reactions using in situ distributions of nitrogen species and their 15N signatures 2) Measure specific rates of reactions using labeled nutrient spikes and selective inhibitors 3) Culture organisms of interest4) Use DNA sequencing to determine the distributions of attached and free living microorganisms5) Conduct mRNA analyses to determine which bacteria are functionally active.Kuypers. (2003) Nature 422: 608-611.15N: Incubations of 15N-NH4+ and 14N-NO2-Anammox in the Black SeaLadderane LipidsNutrientsO215N spikenote: 2000 and 2001note: 15N enriched near surface N2There is a big N2 maximum but it is depleted in 15N-N2!!SoThe distributions of NO3- + NH4+ suggest anammoxat sө = 15.95There is a big maximum in N2/Ar at the right depthBut d15N2 is quite variable and can be very depleted.If N2 was made by total consumption of NO3 + NH4 it’s d15N would be +6 to +8‰Clearly there are additional fluxes or processes we need to understand.Conclusions from Geochemistry1. Temporal variability in 15N-N22. Anammox bacteria free-living3. Denitrifiers particle attached4. Our Hypothesis that that variability seen in anammox / denitrification is due to variability in organic rich particulate aggregates.The redox state inside particles is more reducing than outside15N-NO3- and 15N-NH4+ Total consumption by anammox should produce N2 with d15N = 6-8‰!15N-NO3-15N-NH4+ 0 4 8 12 16 2015N171615141312Sigma Theta Knorr 2001 & 200315NH4+ St 12 Knorr 200315NH4+ St 2 Knorr 200115NO3- St 12 Knorr 200315NO3- St 20 Knorr 200315NO3- St 2 Knorr 200115NO3- St 14 Knorr 200115NH4+ (Velinsky, 1991)N2 was measured as N2/ArAr was determined in 2005T increases with depthAr decreases with depthAr always supersaturated An Ar – Temperature Relationshipwas derived and used to estimate Ar for all years. CILUse Ar to Calculate Excess N2TempTemperature Solubility versus Mixing SolubilitySolubility versus mixingCauses of Deviations from Equilibrium for N2:1. bubble or air injection (+); heating (+) and cooling