Phytop l anktonNutrien t sZoopla nktonPhytop l anktonRecycledNutrien t sZoopla nktonOxidizedNutrien t sDetritusCritical DepthRest ofOceanBiological and Solubility PumpsNew (Export) vs. Regenerated ProductionFisheriesCO2 SequestrationNitrateAmmoniumAdapted from Chisholm 2000• Redfield (1958)• Dugdale & Goering (1967)• Eppley & Peterson (1979)• Shuter (1979)Assumptions:• We have chosen a box large enoughto balance out advection and diffusion• Everything, on average, is in steady-state• Because it is in steady state, we can assume Redfield-Ratios• There must be mass balance (nothing appears ordisappears)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”surface nitrateconcentration.Vigorous fluid mixingintroduces a net flux ofnitrate (read nutrients)into the surface, well-litlayer.Laws et al., 2000VGPM-derived Carbon ExportLaws et al., 2000Large Scale PatternsKudela et al., 2005, Oceanography 18: 185-197Seasonal PatternsKudela et al., 2005, Oceanography 18: 185-197New (Export) vs. Regenerated ProductionFisheriesCO2 SequestrationNitrateAmmoniumAdapted from Chisholm 2000• Redfield (1958)• Dugdale & Goering (1967)• Eppley & Peterson (1979)• Shuter (1979)Zehr & Kudela, 2011, Annu. Rev. Mar. Sci, 3: 197-225Summary Points:! The conceptual N cycle (and therefore new/regeneratedproduction) is in a state of flux, with new organisms andprocesses being discovered (and unknown globalimplications)! Although there are hypotheses about the global Nbalance, and how the N cycle may be affected by globalclimate change, there are too many unconstraineduncertainties and we therefore can only predict the mostobvious responses to past or future climate changeZehr & Kudela, 2011, Annu. Rev. Mar. Sci, 3: 197-225Sediment 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 • (!’-!) /!•vVelocitygravityDensity•ViscosityradiusParticle density - waterApplications of Stoke!s LawV = 2 / 9 • g • r2 • (!’-!) /!•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….Martin Equation:F=Fz(Z0/Z)^b(b=-0.833 for Monterey)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 of growth andbiomass of phytoplankton! On average, biomass is in Redfield-proportions for C:N:P:O(:Si)! Large cells are capable of faster uptake due to internalpools and surge kinetics! Only cells growing near !max are Redfield! Export production mass decreases logarithmically withdepth! Therefore, diatoms and other large, heavy cells areextremely