Puget Sound Oceanography 2011 Nutrients
Feb 10, 2016
Puget Sound Oceanography 2011
Nutrients
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.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.
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
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
Fraser River: timing of flow
Feb. peaknitrate concentration
summer minimumnitrate concentrationflow
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
Short-term variability in surface concentrations:
1972 USGS survey
Riverine sources of nutrients
Where does the N go?(Total inputs = 2600-3100 tonnes
/day)losses
We have become the dominant source of nitrogen fixation on the Earth – partly by making
fertilizerand partly by growing legumes