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Puget Sound Oceanography 2011

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.

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Puget Sound Oceanography 2011

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  1. Nutrients Puget Sound Oceanography 2011

  2. Deviation from Redfield Ratios:

  3. 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.

  4. Units you’ll see in the literature: Use the element’s molecular weight to convert: e.g., 1 µg-at l-1 of nitrogen = 14 µg N l-1

  5. 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 1997 • 1 tonne = 1000 kg

  6. Fraser River: timing of flow Feb. peak nitrate concentration summer minimum nitrate concentration flow

  7. But, nutrient limitation is found in Puget Sound! Nitrate+Nitrite from 1998-2000 PRISM samples Mackas and Harrison 1997 Newton et al, 2002 Washington State Marine Water Column Quality Report

  8. Short-term variability in surface concentrations:

  9. Riverine sources of nutrients 1972 USGS survey

  10. Where does the N go? losses (Total inputs = 2600-3100 tonnes /day) • Estuarine surface-layer advection of particulate and dissolved nitrogen: • As phytoplankton: 2100-2400 tonnes /day • As zooplankton: 55 tonnes / day • As PN and DON: 265 tonnes / day • [net inputs=500-700 tonnes / day] • Primary Production uptake = ~1500 tonnes N / day • So, ~30% of this is ‘new’ production from the N inputs • Harvest removal = 2 tonnes / day • Sedimentation and burial = ~100 tonnes / day • Denitrification = <1.5 tonnes / day • Top predators = ~1 tonne / day

  11. We have become the dominant source of nitrogen fixation on the Earth – partly by making fertilizerand partly by growing legumes

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