puget sound oceanography 2011
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Nutrients. Puget Sound Oceanography 2011. Deviation from Redfield Ratios:. The Nitrogen Cycle. “Nitrogen Fixation” We can make ammonia in factories, using atmospheric nitrogen and hydrogen (usually from natural gas or petroleum). Lightening makes about 5-8% of the total nitrogen fixed. - PowerPoint PPT PresentationTRANSCRIPT
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Puget Sound Oceanography 2011
Nutrients
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Deviation from Redfield Ratios:
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The Nitrogen
Cycle
“Nitrogen Fixation”We can make ammonia in factories, using atmospheric nitrogen and hydrogen (usually from natural gas or petroleum).Lightening makes about 5-8% of the total nitrogen fixed.Nitrogen-fixing bacteria (marine cyanobacteria, or living symbiotically with legumes).Denitrifying bacteria, particularly ones living in anaerobic conditions, use nitrate as a substitute for oxygen in their metabolism. Produce N2 gas as a by-product.
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Units you’ll see in the literature:
Unit Abbreviation
Meaning
microgram-atoms per liter
µg-at l-1 10-6 g-atoms per liter
milligram-atoms per cubic meter
mg-at m-3 10-3 g-atoms per m3
[=µg-atom per liter]Micromolar µM
[not µM l-1]10-6 moles per liter
micromoles per liter
µmol l-1[not µM l-1]
10-6 moles per liter[=µM]
millimoles per cubic meter
mmol m-3
[not mM l-1]10-3 moles per m3
micrograms per liter
µg l-1 10-6 grams per liter[=parts per billion]
milligrams per liter mg l-1 10-3 grams per liter[=parts per million]
metric tonne tonne 1000 kgUse the element’s molecular weight to convert:e.g., 1 µg-at l-1 of nitrogen = 14 µg N l-1
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Salish Sea nitrogen inputs• Ocean: 30 µM; 2600-2900 tonnes /day• Sewage inputs:
• Vancouver: 20-22 tonnes / day• Seattle: 15-16 tonnes / day• Total sewage: <100 tonnes / day
• Rivers and Runoff: • Fraser River: 2-4µM; 50 tonnes / day• Skagit River: 2-4µM; 7 tonnes / day • Total Rivers+Runoff: <75 tonnes / day
• Atmospheric inputs: <10 tonnes / day
From Mackas & Harrison 19971 tonne = 1000 kg
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Fraser River: timing of flow
Feb. peaknitrate concentration
summer minimumnitrate concentrationflow
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Mackas and Harrison 1997Newton et al, 2002 Washington State Marine Water Column Quality Report
But, nutrient limitation is found in Puget Sound!
Nitrate+Nitritefrom 1998-2000 PRISM samples
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Short-term variability in surface concentrations:
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1972 USGS survey
Riverine sources of nutrients
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Where does the N go?(Total inputs = 2600-3100 tonnes
/day)losses
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We have become the dominant source of nitrogen fixation on the Earth – partly by making
fertilizerand partly by growing legumes