Our Conceptual Model
Jan 12, 2016
Our Conceptual Model
1 2 43 5 6 70
4
6
8
10
12
14
Nitrate (uM)
JUL- SEPT
Seasonal cycle of nutrients and temperature on the crest of Georges Bank
Pastuzak et al., 1982
Nutrient Recharge is Across the Flanks…
in Fall, not Winter
The “Donut” Hypothesis of Post-Bloom Nutrient Injections & Production
Presumed Greater Production on NE Peak…
CRITICAL DEPTH
Z=1.0 Zcr=1.4
[DIN]Seasonal Changein Critical Depth
SeasonalChange in
Position of Front
Ratio (R) =Mixing Depth
Critical Depth “Production Velocity”
Subsurface Chl. Max. Proportional to
Compensation Depth (notcritical depth)
And Production = f(Ratio, [N])
R = 1.4 R = 1.0
DIN PON
Sources of, and what happens to, dissolved inorganic nutrients that are brought onto Georges Bank
Ammonia Silicate
SmallPhytoplankton
LargePhytoplankton
SmallZooplankton
LargeZooplankton
DetritusNitrogen
DetritusSilica
PredationMortality
Remineralization
UptakingUptaking Uptaking
Dissolution
Fecal
Mortality
Grazing Grazing
Mortality
Mortality
Nitrate
GrazingMortality
Biological Model (Rubao Ji, UMass Dartmouth)
Proposed Modeling Experiments:Seasonal Cycle and Transects…
Divergent Upwelling onNE & SW Portions?
Another Interesting Angle…
Giving Two Phytoplankton Patches?
-71 -70 -69 -68 -67 -66 -65
40
41
42
-71 -70 -69 -68 -67 -66 -65
40
41
42
-71 -70 -69 -68 -67 -66 -65
40
41
42
-71 -70 -69 -68 -67 -66 -65
40
41
42
-71 -70 -69 -68 -67 -66 -65
40
41
42
-71 -70 -69 -68 -67 -66 -65
40
41
42
-71 -70 -69 -68 -67 -66 -6540
41
42
-71 -70 -69 -68 -67 -66 -6540
41
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-71 -70 -69 -68 -67 -66 -6540
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42
-71 -70 -69 -68 -67 -66 -6540
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-71 -70 -69 -68 -67 -66 -6540
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-71 -70 -69 -68 -67 -66 -65
40
41
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-71 -70 -69 -68 -67 -66 -65
40
41
42
-71 -70 -69 -68 -67 -66 -65
40
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42
-71 -70 -69 -68 -67 -66 -65
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-71 -70 -69 -68 -67 -66 -65
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-71 -70 -69 -68 -67 -66 -65
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42
(ug/L)0.0
1.6
3.2
4.8
6.4
8.0
9.6
11.2
12.8
14.4
16.0
1997 1998 1999
Jan
Feb
Mar
Apr
May
Jun
Surface Chlorophyll
All Data
What about interannual
variability intiming of the
spring bloom?
Evidence of NE & SW Patches?
Jan
Feb
Mar
Apr
May
Jun
1998 1999
Chl a ug/L
Available SeaWiFS Images:
Monthly Composites
False Start in 1998
Earlier Start in 1999…
Delta t /m
EL9905 SB911 CTD Casts (n=89)
Station Depth (m)
Dep
th (
m)
Calm sunny days led to atypical structure (shallow thermocline) during part of the frontal study
front
Shelf regions were therefore defined by T ( ºC) from 5 m to bottom: <1 = crest; 1-2 = front; >2 = strat.
Mean No. m-3 x 104
Dep
th (
m)
Copepodites
Nauplii
Mixed (n= 3 profiles) Front (n=8) Stratified (n=17)
0 100 200 300 400 500
C. finmarchicus
Centropages
Metridia
Oithona
Pseudocalanus
Temora
0 200 400 600 800 1000 1200 1400
C. finmarchicus
Centropages/Temora
Oithona
Pseudocalanus/Metridia
0 100 200 300 400 500
C. finmarchicus
Centropages
Metridia
Oithona
Pseudocalanus
Temora
0 200 400 600 800 1000 1200 1400
C. finmarchicus
Centropages/Temora
Oithona
Pseudocalanus/Metridia
0 100 200 300 400 500
C. finmarchicus
Centropages
Metridia
Oithona
Pseudocalanus
Temora
0 200 400 600 800 1000 1200 1400
C. finmarchicus
Centropages/Temora
Oithona
Pseudocalanus/Metridia
-5 5 15 25
1
2
3
4
5
6
7
Copepodites
Nauplii
Mixed (n= 3 profiles) Front (n=8) Stratified (n=17)
n = 14,254 identifications, 249 samples, 29 profiles; variances available but not plotted
Taxonomic Composition
Size Category
Leng
th (
mm
)
Size Bins Used for Copepod Lengths
0 5 10 15 20 25
1
2
3
4
5
6
7
0 5 10 15 20 25
1
2
3
4
5
6
7
0 5 10 15 20 25
1
2
3
4
5
6
7
0 5 10 15 20 25
1
2
3
4
5
6
7
0 5 10 15 20 25
1
2
3
4
5
6
7
0 5 10 15 20 25
1
2
3
4
5
6
7
Mixed (n= 3 profiles) Front (n=8) Stratified (n=17)
Mean No. m-3 x 103 at 15 – 20 m depth
Mean No. m-3 x 103 at 25 – 30 m depth
Particle size spectrum and abundance at two depth intervals
-5 5 15 25
1
2
3
4
5
6
7
Copepodites
Nauplii
Mean No. m-3 x 104
Dep
th (
m)
Copepodites
Nauplii
Mixed (n= 3 profiles) Front (n=8) Stratified (n=17)
Crest
Front
Middle ShelfDep
th (
m)
Proportion
Larval cod from 1 m MOC, May 1999, Greg Lough
Size (mm) No. m-2