1. Puget Sound Oceanography 2011 Nutrients

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 N 2 gas as a by-product.

4. Units you’ll see in the literature: UnitAbbreviationMeaning 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 m 3 [=µg-atom per liter] MicromolarµM [not µM l -1 ] 10 -6 moles per liter micromoles per literµmol 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 m 3 micrograms per literµg l -1 10 -6 grams per liter [=parts per billion] milligrams per litermg l -1 10 -3 grams per liter [=parts per million] metric tonnetonne1000 kg Use the element’s molecular weight to convert: e.g., 1 µg-at l -1 of nitrogen = 14 µg N l -1

6. 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

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

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

9. Short-term variability in surface concentrations:

11. 1972 USGS survey Riverine sources of nutrients

14. Where does the N go? (Total inputs = 2600-3100 tonnes /day) losses 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

15. We have become the dominant source of nitrogen fixation on the Earth – partly by making fertilizer and partly by growing legumes