1. Puget Sound Oceanography
Jan. 24, 2011

2. †All but the Fraser River are dammed.
Comparison among rivers:
River
mean flow (m3/s)
range
Peak flow
Min flow
mean
NO3 (uM)
tonnes NO3 per day
Mississippi
12,000
7,000–20,000 m3/s
Spring
Sept/Oct
100
2500
*nitrate conc. and flow timing directly correlated
Susquehanna
1,200
50-5,500 m3/s
Winter/spring
Summer
50 (summer) –
100 (spring)
60 (summer)-
Fraser
3,500
1,700-3,700 m3/s
early Summer
Jan/Feb
2 (summer) –
15 (winter)
<50
*nitrate conc. and flow timing inversely correlated
Skagit
450
m3/s 7
†All but the Fraser River are dammed.

3. Puget Sound nutrients:
Primarily come from the ocean (>90%)
Relatively minor inputs from rivers, run-off, and sewage treatment plants
Seasonality of rivers (low flow and low nutrient conc. in summer) limits influence
Limited threat of eutrophication in PS as a whole
BUT –
ocean water comes in deep and must be mixed to surface
Rivers/run-off come in at surface
Many smaller rivers/run-off come into sheltered, stratified inlets/bays with limited connection to the ocean
So, some areas vulnerable to effects of anthropogenic nutrient inputs

4. Primary Production

5. Productivity and Predictability of Marine Habitats
Coral Reefs
Estuaries
Continental
Shelf
Coastal
Upwelling
Predictability
Open
Ocean
100
300
1000
Productivity (g C m-2 y-2)

6. g C m-2 d-1
Phytoplankton Production across different systems g C m-2 d-1 (net) min season to max season range and median ( • )
From Mann (2000) Ecology of Coastal Waters, 2nd Ed., Blackwell Science, MA, 406 pp.

7. Main Controls on Primary Production
Light
Nutrients
Temperature

8. Extinction of light in water follows a negative exponential:
Depth of the euphotic zone is defined by the 1% light depth (z1%)
% of surface irradiance
100
Beers-Lambert law:
Iz is irradiance at depth
I0 is surface irradiance
kz is the extinction coefficient
z is depth
Depth
The euphotic zone is defined as the depth to which 1% of the surface irradiance penetrates.
Extinction of light in water follows an exponential decrease, with the rate of decrease dependent on the extinction coefficient.
Attenuators:
Water
CDOM
Particles (sediments, phytoplankton, etc.)

9. Light penetration into water
Light intensity at depth (W m-2)
Depth (m)
Light penetrates even less into coastal water than it does into clear water at night!
kz m-1
Clarke and Denton
1962

10. Phytoplankton specific-growth rate, d-1
Temperature [°C]
Matrix of phytoplankton growth rates as f(I,N,T)
Nitrate [µM]
Irradiance [µmol m-2 s-1]
R. Reynolds

12. Sverdrup’s Critical Depth Hypothesis:
Metabolism (photosynthetic rate)
Depth
Critical Depth
Net increase
Net decrease
(includes all losses, respiration, grazing, mortality)

13. Depth of the mixed layer
Well-mixed conditions:
Stratified conditions:
Salinity profile
Salinity profile
Depth
Depth
Well-mixed - MLD is deeper than Critical depth, so no bloom can form.
Stratified – relationship between MLD and CD determines whether plankton can bloom.

14. Observations:
Classic illustration of critical depth theory from observations (from Sverdrup, 1953)

15. Controls on chlorophyll biomass:
(growth –
respiration –
grazing)
Horizontal advection
Mixing
depth
Vertical advection and sinking
Growth = (Light, Nutrients, Temp.)
temperature
Chlorophyll = growth – respiration +/- horizontal advection – vertical advection – mixing – sinking - grazing

16. How do circulation differences in Puget Sound effect phytoplankton
production and biomass?

17. Seasonal cycles of chlorophyll across the basins:5 10 15 20 25 1 2 3 4 6 7 8 9 11 12
Month
Three Tree Point, Main Basin
Gedney Island, Whidbey Basin
N.Admiralty Inlet
Sisters Point, Hood Canal
Oakland Bay, South Sound
Chl a (µg L-1)
Which basin is which?

18. Differences in Residence Time: [from Babson et al, 2006]
Basin Residence time (days) Rank order
(longest to shortest)
Main
Surface
Deep
South Sound
Surface
Deep
Whidbey
Surface 5 5
Deep
Northern Hood Canal
Surface 8 4
Deep
Southern Hood Canal
Surface
Deep

19. For more info see Newton et al, 2002 Washington State Marine Water Column Quality Report

20. (short residence time)
Categorization of PS basins:
Hood Canal
Main Basin
Whidbey Basin
Strait of Juan de Fuca
Dabob Bay
Sills
Well-mixed
(long residence time)
Poorly-flushed
(short residence time)
Well-flushed
Figure 5.9 Relative productivities of Puget Sound inlets. Compared to the main basin, which seems to have a nearly optimal balance of mixing and flushing for phytoplankton growth, other areas of the Sound are less productive. They may be flushed and mixed too much (as at the sills) or not enough (as in inlets), or another combination of suboptimal conditions.
Main basin has perfect balance of stratification, mixing, and flushing.
Strongly-stratified
From Strickland, The Fertile Fjord

21. Seasonal cycles of chlorophyll across the basins:5 10 15 20 25 1 2 3 4 6 7 8 9 11 12
Month
Three Tree Point, Main Basin
Gedney Island, Whidbey Basin
N.Admiralty Inlet
Sisters Point, Hood Canal
Oakland Bay, South Sound
Chl a (µg L-1)
Which basin is which?