Marine Nutrient Cycleshttp://upload.wikimedia.org/wikipedia/commons/1/13/Nutrient-cycle_hg.pngNutrients are those elements that are incorporated into biomass and may limit growth2Macronutrients:C, H, N, O, P, SMicronutrients:Fe, Cu, Mo, V, etc.Other Elements with Physiological Function:Na, K, Ca, Mg, etc.Generalized Equation for Organic Matter Fixation:106 CO2+ 16 NO3+ HPO4+ 122 H2O + 18 H C106H263O120N16P1inorganicorganicNitrogen and Phosphorus Cycles“Redfield Ratio” 106C : 16N : 1PAverage Composition of Living BiomassPhytoplankton-based, does not include structural carbon (trees, seaweeds, skeletons e.g. corals)Ecological Stoichiometry:The general idea is that biomass (mostly plant) production requires that nutrients be supplied in optimal ratios, and departures from those ratios in the availability of nutrients have ecological consequences – slow growth, altered physiology, etc.Not all forms of nutrient elements are equally availableNutrient elements cycle between reservoirs (rocks, biomass, dissolved in water, adsorbed onto clay particles, etc. – depends on the geochemistry of the element)Generalized Equation for Organic Matter Production:106 CO2+ 16 NO3+ HPO4+ 122 H2O + 18 H C106H263O120N16P1P in cell:ATP, DNA, RNA, phospholipidsPhosphorus Cyclephytoplankton zooplanktonPO4DOP & POPeuphotic zonefast loop87%PO4DOP & POPsinkingupwellingwind mixingrelativelyfast loop99%sedimentslow loopPhosphorus Cycle in the OceanPycnoclineYears to Centuries100 million years100 cycles x 1000 yearsWeeksMajor reservoirNo gaseous phaseA typical phosphorus atom, released from the rock by chemical weathering, may enter and cycle within the terrestrial community for years, decades or centuries before it is carried via the groundwater into a stream. Within a short time of entering the stream (weeks, months, or years), the atom is carried to the ocean. It then makes, on average, about 100 round trips between the surface and deep waters, each lasting perhaps 1000 years. During each trip, it is taken up by surface-dwelling organisms, before eventually settling into the deep again. On average, on its 100thdescent (after 10 million years in the ocean), it fails to be released as soluble phosphorus, but instead enters the bottom sediment in particulate form. Perhaps 100 million years later, the ocean floor is lifted up by geological activity to become dry land. Thus, our phosphorus atom will eventually find its way back via a river to the sea, and to its existence of cycle (biotic uptake and decomposition) within cycle (ocean mixing) within cycle (continental uplift and erosion).Generalized Equation for Organic Matter Fixation:106 CO2+ 16 NO3+ HPO4+ 122 H2O + 18 H C106H263O120N16P1Nitrogen CycleP in cell: ATP, DNA, phospholipidsinorganicorganic(or NH4)proteins, chlorophyll, nucleic acidsN in cell:phytoplankton zooplanktonNH4DON & PONNH4DON & PONsinkingNitrogen Cycle in the OceanammonificationNO3N2nitrificationNO3upwellingwind mixingdenitrificationN2Nitrogen fixationPONburialNitrogen Transformationslightning nitrogen-fixing bacteriaindustrial fixation – “Haber Process”NitrificationNH4NO3aerobiclight-inhibitedDenitrificationNO3, NO2N2anoxic processN2fixationN Natmospheric N: NH4Organic NNo atmospheric reservoirMajor ReservoirsinorganicPONammonificationnitrificationNitrogen Regeneration During Decomposition of PhytoplanktonLoadings Scale with Population DensityAnnual Production of Fixed Nitrogen is Increasing
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