Biological and Solubility PumpsNew (Export) vs. Regenerated ProductionFisheriesCO2 SequestrationNitrateAmmoniumAdapted from Chisholm 2000• Redfield (1958)• Dugdale & Goering (1967)• Eppley & Peterson (1979)• Shuter (1979)• Redfield (1958)• Dugdale & Goering (1967)• Eppley & Peterson (1979)• Shuter (1979)Estimating New Production In Vitro 14C Assimilation hours-->day O2 evolution hours-->day 15N measurements hours-->day 18O2 evolution hours-->day Physical Transport Sediment traps days-->months Bulk Property NO3 flux to photic zone hours-->days OUR below photic zone seasonal-->annual 238U/234Th 1-300 days Other Remote Sensing days-->weighted annual Optimal energy conversion instantaneousReconciling Time-Space ScalesSource: http://daac.gsfc.nasa.gov/CAMPAIGN_DOCS/OCDST/nab.htmlFRRFPvsEIncubationsSediment TrapsMass BalanceSteady State?Eppley &Peterson,1979• Defined the f-ratio• Determined thatthere are worldwidepatterns in exportproduction• Can estimateexport from totalproductivityBehrenfeld and Falkowski. 1997. L+O 42:1-20IP = 0.66125 PBopt Chlopt zeu tirr IoIo!+!4.1 [mg C m-2 d-1]PBopt - maximum C fixation rate per unit chlorophyllChlopt - chlorophyll concentration at the depth of PBoptzeu - euphotic depthtirr - photoperiodIo - surface irradianceHypothesis: A large body of evidence leads to theconclusion that light limits the growth of phytoplankton.The distribution of phytoplankton should reflect thedistribution of light.012345670 500 1000 1500 2000 2500Irradiance(µmol quanta m-2 s-1)PhotosynthesismgC (mg Chl)-1 h-1“High Light” Cells“Low Light” CellsBut…it looks like light kills phytoplankton.Hypothesis rejectedHypothesis: There is also evidence leads to the conclusionthat higher temperatures enhance the growth ofphytoplankton. The distribution of phytoplankton shouldreflect the distribution of surface temperature.Temperature (oC)Looks like phytoplankton have a low boilingpoint. Hypothesis rejected.SSTWell, its not light,not temperature,what could it be?Mixed Layer DepthsMar.Aug.A simple calculation, but a complex interaction….Annual “average” surfacenitrate concentration.Vigorous fluid mixingintroduces a net flux ofnitrate (read nutrients) intothe surface, well-lit layer.Laws et al., 2000VGPM-derived Carbon ExportSediment TrapsStokes LawQ: How long does it take for a particle tosink in the ocean?A: We need to know 3 things:1) density of the particle2) radius of the particle3) density of seawaterThen we use Stokes Law:V = 2 / 9 • g • r2 • (ρ’-ρ) /ρ•vVelocitygravityDensity•ViscosityradiusParticle density - waterApplications of Stoke’s LawV = 2 / 9 • g • r2 • (ρ’-ρ) /ρ•vV = 2.62 • 104 • r2Simplification forspherical particleswith densities nearthat of rockr = 3 to 40 micronsr = 3 to 40 x10-4 cmV = 2.62 • 104 • (3 to 40 x10 -4 )2V = 0.002 - 0.419 cm/s11 to 2300 days to sink!Martin’s Equation (VERTEX)Biomassdecreasesessentiallyexponentiallywith depth….Thorium Fluxes (U238/Th234) Conservative properties follow linear mixinglaws Non-Conservative properties are non-linear inspace and time Some properties fall in-betweenConservative vs. Non-Conservative Temperature Gases Biology Nutrients Salinity Non-reactiveelements Apparent OxygenUtilizationOxygen Utilization RateO2Organic carboninorganic nutrientsTurk et al., 2001Nitrate Mass Balance Equals New (Export) ProductionReconciling Time-Space ScalesSource: http://daac.gsfc.nasa.gov/CAMPAIGN_DOCS/OCDST/nab.htmlFRRFPvsEIncubationsSediment TrapsMass BalanceSteady State?Large Cells = High BiomassFrom Chisholm, 1992Figure 3, 8 Wilkerson et al. 2000, DSR 47:1003-1022Adding it all up…. There are limiting elements to both the rate ofgrowth and biomass of phytoplankton On average, biomass is in Redfield-proportionsfor C:N:P:O (:Si) Large cells are capable of faster uptake due tointernal pools and surge kinetics Only cells growing near µmax are Redfield Export production mass decreaseslogarithmically with depth Therefore, diatoms are extremely
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