““Only those that intend the absurd,Only those that intend the absurd,achieve the impossibleachieve the impossible””EscherEscherOCNG 251: OceanographyOCNG 251: OceanographyTuesday, Dec. 04Tuesday, Dec. 04thth, 2008, 2008a.a.The chemistry of Life and BiogeochemicalThe chemistry of Life and BiogeochemicalCyclesCyclesc.c.Nutrient cyclesNutrient cyclesd.d.The carbonate system and the Carbon The carbonate system and the Carbon cyclecyclee.e.Ocean AcidificationOcean Acidificationf.f.Coastal hypoxiaCoastal hypoxiaBiogeochemical CyclesBiogeochemical CyclesA simple thing, really…Defining the Ocean EcosystemDefining the Ocean EcosystemThere exists an inseparable relationship between the flow ofThere exists an inseparable relationship between the flow ofenergy and the flow of nutrient elements (i.e. N, P, K, Ca, etc)energy and the flow of nutrient elements (i.e. N, P, K, Ca, etc)!! The The flow of energy and materialsflow of energy and materials (i.e. water, chemicals) into and (i.e. water, chemicals) into andout of biological communities out of biological communities definesdefines ecosystem studies ecosystem studiesChemical Elements (the Periodic Table)and those essential for life" Of the 103 elementsin the Periodic Table,only 24 are requiredby organismsorganismsRequired elt Required for some life formsToxic elt""Macronutrients:Macronutrients:Required in largeRequired in largeamountamount ((““Big SixBig Six””: C,: C,N, P, S, O, H)N, P, S, O, H)""Micronutrients: smallMicronutrients: smallor moderate amountor moderate amountChemistry of LifeChemistry of Life……Chemical Elements - Essential for lifeCarbon" Carbon forms three-dimensional molecules of large sizeand complexity in organic (carbon-containing) compoundsthat form large molecules (amino acidsacids, sugars, enzymes,DNA), and other chemicals vital to life on Earth.Chemical Elements - Essential for lifeNitrogen""NitrogenNitrogen (along with carbon) is the essential element thatallows formation of amino acids (! proteins) and DNA.Proteins contain up to 16% NChemical Elements - Essential for lifePhosphorus""Phosphorus is the Phosphorus is the ““energy elementenergy element”” occurring in compounds occurring in compoundscalled ATP and ADP important for energy transfer processescalled ATP and ADP important for energy transfer processesand DNA.and DNA.Chemical Elements - Essential for lifeCarbon:Nitrogen:Phosphorus Ratios" Organisms actively concentrate certain elements essential forlife: ! Algae concentrate Iron (Fe) 100,000 times vs. itsconcentrationconcentration in the Ocean• Most organisms keep a ratherconstant chemical compositioncomposition! Algae and plankton C:N:Pratio of 106:16:1 (RedfieldRatio)! Soil microbes maintain arelatively constant proportion ofnutrients in their biomass (andat higher levels than the OMthey decompose)Chemical Elements - Essential for life• Availability of some elements (particularly N & P) is oftenlimited and the supplysupply of these elements may control the rate(or type) of primary production in ocean ecosystems.• External sources of nutrients are varied ! Recyclingdominates most inputs of limiting elements (N, P, K)Biogeochemical cycles in the OceanBiogeochemical cycles in the OceanCO2(gas) + H2O + Nutrients (N,P) + Energy ! OM + O2 (gas)The carbonate system and the Carbon cycleCO2(gas) dissolves readily in water and forms carbonic acid(H2CO3). However, at pH of natural waterswaters, carbonic acidequilibrates as bicarbonate (HCO3-: 80%)CO2(gas) + H2O ! H2CO3 ! H+ + HCO3- ! H+ + CO32- + Ca2+! CaCO3The carbonate system and the Carbon cycleCa+ + CO32- ! CaCO3 (solid)Formation of CaCO3 skeleton parts by micro-organisms ashard part: " foraminifersforaminifers, coccolithophorids, pteropodsto precipitate CaCO3.The carbonate system and the Carbon cyclethe Carbon cycleCa+ + CO32- ! CaCO3 (solid)Ocean surface waters are nearly everywheresupersaturated with respect to calcium carbonate.However, no spontaneousspontaneous precipitation occurs! (inhibitionfrom Mg2+ in solution)"Intervention of marine organisms (foraminifers,coccolithophorids, pteropods) to precipitate CaCO3.- CaCO3 dissolves readily with decreasing temperature andincreasing pressure. Also,- Calcite and Aragonite have the same formula butdifferent crystalline structure. Aragonite is less stable.The carbonate system and the Carbon cycleAs organic matter (OM) “rains”to the sea floor, it is mostlydegraded (>90% regeneration!)" production of CO2" increasedincreased formation of acid" increased dissolution ofcarbonates!CO2(gas) + H2O ! H2CO3 ! H+ + HCO3- ! H+ + CO32- ! CaCO3The carbonate system and the Carbon cycleCO2(gas) + H2O ! H2CO3 ! H+ + HCO3- ! H+ + CO32- ! CaCO3Where should you find carbonate sedimentationsedimentation?Where should you not find it?The carbonate system and the Carbon cycle CarbonateCarbonate Compensation Depth (CCD): the depth atwhich all carbonates have dissolved" The CCD is shallower for Aragonite that for calciteCO2(gas) + H2O ! H2CO3 ! H+ + HCO3- ! H+ + CO32- ! CaCO3Ocean Acidification IncorporationIncorporation of anthropogenic CO2 to the oceanCO2(gas) + H2O ! H2CO3 ! H+ + HCO3- ! H+ + CO32- ! CaCO3Ocean Acidification IncorporationIncorporation of anthropogenic CO2 to the oceanCO2(gas) + H2O ! H2CO3 ! H+ + HCO3- ! H+ + CO32- ! CaCO3Biogeochemical cycles in the OceanBiogeochemical cycles in the OceanCO2(gas) + H2O + Nutrients (N,P) + Energy ! OM + O2 (gas) Dissolved (trace) nutrients in the OceanDissolved (trace) nutrients in the OceanCO2(gas) + H2O + Nutrients (N,P) + Energy ! OM + O2 (gas) NitrogenPhosphorusThe silicon cycleSilicon behaves like a nutrient" Minor element" essential for formation offrustules" undersaturated in the Oceans" Micro-organismsorganisms (diatoms,radiolaria) can still use it!" More soluble in cold waters." No Compensation Depth: Slowdissolution despiteundersaturation!Where should you find silicate sedimentation?Where should you not find it?Distribution of Ocean SedimentsNutrient over-enrichment from anthropogenic sources isone of the major stresses impacting coastal ecosystems.Generally, excess nutrients lead to eutrophic conditions andincreased algal production which in turnturn increases theavailability of organic carbon within the aquatic ecosystem.Both the near-coastal hydrodynamics that generate watercolumn stratification and the nutrients that fuel primaryproductivity contribute to the formation of hypoxic zones.Human activities on land can add