Spatial and Temporal Distributions of PhytoplanktonRed Tide Bloom, California CoastSpatial distributions of phytoplankton reflect the balance of forces controlling growth, dispersal and mortalityThis is obvious, but identifying and understanding those forces isn’t always so easyGlobal distributions, simplistically, can be seen as light limited or nutrient limited. Light limitation important in high latitude regions or coastal areas of high turbidity. These regions tend to have strong spring bloomsNutrient limitation everywhere else, though limiting nutrient may vary: N, P, Fe, Si…Grazing usually more important in adjusting seasonal cycle than in bloom formation.Exception: shallow water where benthic grazing is significantSummaryPhotosynthesis and Primary ProductionPrimary Production = Carbon fixed = DIC converted to organic C = biomass produced, integrated over space and/or time90% of the primary production in the ocean is done by phytoplankton.How many are there?How fast are they growing?Phy toplanktonPhytoplankton Biomass DeterminationCount them using a microscope Count them using a flow cytometerMeasure a specific biochemical (pigments, esp Chlorophyll)Phytoplankton IdentificationMicroscopyPigmentsDNA (16/18 S rRNA or other marker gene – photosystem, RuBisCOPrimar y Production• Gross P. P. (GPP)• Net P. P. (NPP)light energyC6H12O6+ 6O26 H2O + 6 CO26 H2O + 6 CO2Measuring Primary Productionlight energyC6H12O6+ 6O21.14C method1414Add 14C labeled bicarbonate, incubate, filter, acidify (converts bicarbonate to CO2, measure residual 14C (presumed to be in organic matter)Gross or Net?lightdarkMeasuring Primary Production2. Light/Dark bottle methodlightdarklight energyC6H12O6+ 6O26 H2O + 6 CO2Compare changes in oxygen concentration through timeGross or Net?Measuring Primary Production3. Fluorescence Yieldlight energyC6H12O6+ 6O26 H2O + 6 CO2Based on the physiology of photosynthesis:“Pump and Probe Fluorometer” also called“Fast Repetition Rate Fluorometer”Blast the cell with light, blast it again a few mseclater, measure fluorescenceGross or Net?Factors that affect primary productionLightSpring Phytoplankton BloomAn extremely important signal for all kinds of biology in the oceanTriggered by changes in light availabilityCritical Depth Model (Sverdrup 1953)P = Phytoplankton biomass, model assumes it starts off evenly distributed through the water columnBased on balancing photosynthesis and respiration in a population of plants cycling through the water column –irradiance varies with depthThis conceptual model applies to other primary producers dealing with variable irradiance: benthic algae (seaweeds), sea grasses, cor als, understory vegetation in forestsComparison of predicted Critical Depth with phytoplankton growthMixing depth exceeds Critical DepthMixing depth less than Critical DepthRange of Critical Depths modeled with two different attenuation coefficientscentricpennatedinosWSSeasonal Cycles are Repeatable EventsPhytoplankton biomass (chl)Nutrient conc.Light levelSeasonal Cycle: Temperate OceanGlobal patterns –Tied to weather (mixing), interannualvariation in irradianceTROPICS: Little Seasonal VariationTEMPERATE: Strong Seasonal Variation –2 PeaksPOLAR: Strong Seasonal Variation –1 peakNutrient LimitationNutrient Addition ExperimentsNutrient Limitation1. Nitrogen vs. Phosphorus2. Trace metals (Fe, Cu, Mg, etc.)Fe additionBottle ExperimentField ExperimentHigh Nutrient, Low Chlorophyll (“HNLC”)Regions where (seemingly) nutrients and light are not enoughThe Equatorial Upwelling Zone AnomalyLots of nitrate and macronutrients, less phytoplankton biomass than expectedNitrate mapSurface Nitrate ConcentrationSources of Fe – benthic regenerationSources of Fe – aeolian transport (dust in the wind…)Sources of Fe – human interventionOne of the IRONEX experimentsA means of remediating fossil fuel CO2? http://www.usc.edu/dept/LAS/biosci/tricho/Reprints/Capone_ASMNews_2005.pdfUpwelling RegionsPhysical processes conspire to provide light and nutrientsChlorophyll TemperatureSimple model of wind‐driven coastal upwelling. Other mechanisms accomplish the same thing in other locations.Interannual variation in upwelling –El Nino cycleDeep Chlorophyll MaximumTransect shown in the next slideDepthAKHIIsopleths of Chlorophyll ConcentrationThis situation is the case most of the time in the subtropical ocean gyresFronts and EddiesEnhanced mixing along isopycnals – nutrient deliveryBloom sequence at Cape Bathurst Polyna (Canadian Arctic). Black = ice cover. Polynas are generally productive regions in polar oceansPolynas –Open water in an ice‐covered seaCaused by wind or currentsIce Algae, A High Biomass Polar HabitatAlgae on the underside of pack ice, Russian Arctic OceanTypical ice algae, here mostly diatoms but also flagellates, protozoa…•Unique to polar regions•Can represent significant biomass•Blooms earlier than phytoplankton because ice matrix holds it in surface layer•Snow cover affects light penetration, thus algal growth (climate feed‐back).•Can be grazed by zooplankton if accessible on bottom of floe•Nutrients from underlying water, brine exclusionIce AlgaeGrowing IN the ice, not as a coating on the bottom. May be integrated as floe thickens by cells swept from the water column by accretion ice or lifted from the bottom but more likely growing in brine channels, slushSeen as a colored layer on the bottom of ice