> Inner Transitional Outer PWS 1.Large zooplankton were collected with 1-m2 square MOCNESS with 500 ...

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Inner

Transitional

Outer

PWS

GLOBEC LTOP cruises in the northern GOA.

Month

Year Mar Apr May July Aug Oct

1997 X

1998 X X X X X

1999 X X X X X

2000 X X X X X

2001 X X X X X X

2002 X X X X X X

2003 X X X X X X

2004 X X X X

1. Large zooplankton were collected with 1-m2 square MOCNESS with 500 m mesh. Samples collected in 20 m depth increments from 100 m to the surface at night.

2. Small zooplankton were collected with a 25 cm diameter CalVET net with 150 m mesh. Vertical tows from 100 m to surface during the day.

3. Water column profiles were collected with a Seabird model 911 plus CTD and fluorometer.

4. Samples were collected during years and months listed below:

Collection Sites:1) 13 Stations along Seward Line (labeled GAK)2) 5 Stations in Prince William Sound (PWS box)3) 4 Stations at Hinchinbrook Entrance (HE)

N. plumchrus & N. flemingeri

Month

Mar Apr May Jun Jul Aug Sep Oct

Mea

n A

bund

ance

(N

o. m

-3)

0

20

40

60

80

100

120

140

160

180

InnerTransOuterPWS

Mean Abundance (No. m-3)

0.0 0.5 1.0 1.5 2.0 2.5

Dep

th (

m)

-120

-100

-80

-60

-40

-20

0

Oithona similis

Month


Mea

n A

bund

ance

(N

o. m

-3)

0

500

1000

1500

2000

2500

3000

3500

InnerTransOuterPWS

Animals widely distributed across the shelf tend to occur in the upper mixed layer day and night

Neocalanus cristatus

Month

Mar Apr May Jun Jul Aug Sep OctM

ean

Abu

ndan

ce (

No.

m-3

)

0

5

10

15

20

25InnerTransOuterPWS


0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6

Dep

th (m

)

-120

-100

-80

-60

-40

-20

0

Eucalanus bungii

Month


Mea

n A

bund

ance

(N

o. m

-3)

0

10

20

30

40

50

InnerTransOuterPWS

Mean Abundance (No. m-3 X 10-1)

0 1 2 3 4 5 6 7

Dep

th (

m)

-120

-100

-80

-60

-40

-20

0

Calanus marshallae

Month


Mea

n A

bund

ance

(N

o. m

-3)

0

10

20

30

40

50

60

InnerTransOuterPWS


0.0 0.2 0.4 0.6 0.8 1.0 1.2

Dep

th (m

)

-120

-100

-80

-60

-40

-20

0

Pseudocalanus spp.

Month


Mea

n A

bund

ance

(N

o. m

-3)

0

1000

2000

3000

4000

5000

InnerTransOuterPWS

Animals restricted to the outer or inner shelf tend to occur between the thermocline and permanent halocline

Ostracods

Month


Mea

n A

bund

ance

(N

o. m

-3)

0

2

4

6

8

10

12

14

InnerTransOuterPWS


0.0 0.5 1.0 1.5 2.0 2.5 3.0

Dep

th (m

)

-100

-80

-60

-40

-20

0

Pasiphaea pacifica

Month


Mea

n A

bund

ance

(N

o. m

-3)

0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

InnerTransOuterPWS


0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6

Dep

th (m

)

-100

-80

-60

-40

-20

0

Pareuchaeta elongata

Month


Me

an

Ab

un

da

nce

(N

o.

m-3 )

0

2

4

6

8

InnerTransOuterPWS


0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8

Dep

th (m

)

-120

-100

-80

-60

-40

-20

0

Cyphocaris challengeri

Month


Me

an

Ab

un

da

nce

(N

o.

m-3

)

0

1

2

3

4

5

6

7

InnerTransOuterPWS


0 2 4 6 8 10

Dep

th (

m)

-120

-100

-80

-60

-40

-20

0

Animals which avoid the upper mixed layer, even at night, occur primarily in the fjord

Thysanoessa spinifera

Month


Mea

n A

bund

ance

(N

o. m

-3)

0.0

0.2

0.4

0.6

0.8

1.0

InnerTransOuterPWS

Mean Abundance (No. m-3 X 10-2)0 2 4 6 8 10

Dep

th (m

)

-120

-100

-80

-60

-40

-20

0

Euphausia pacifica

Month


Mea

n A

bund

ance

(N

o. m

-3)

0.0

0.5

1.0

1.5

2.0InnerTransOuterPWS

Mean Abundance (No. m-3 X 10-2)0 1 2 3 4 5 6 7

Dep

th (

m)

-120

-100

-80

-60

-40

-20

0

Metridia pacifica

Month


Mea

n A

bund

ance

(N

o. m

-3)

0

50

100

150

200

250

300

InnerTransOuterPWS


0 5 10 15 20 25 30 35

Depth

(m

)

-120

-100

-80

-60

-40

-20

0

Thysanoessa inermis

Month


Mea

n A

bund

ance

(N

o. m

-3)

0.0

0.2

0.4

0.6

0.8

1.0

InnerTransOuterPWS


0.0 0.2 0.4 0.6 0.8 1.0 1.2

Dep

th (

m)

-120

-100

-80

-60

-40

-20

0

Diurnal vertical migrators, residing in the upper mixed layer at night and below the permanent halocline during the day tend to be more abundant on the inner shelf (except E. pacifica)


Month


Mea

n A

bund

anc

e (

No

m3 )

-20

0

20

40

60

80

100

120

140

160

180

199719981999200020012002

Neocalanus, an oceanic species, was more abundant in 1998 and 2002 than in 2000 and 2001 (error bar are 95% confidence intervals)

Correlation between major water column properties and abundance of Neocalanus plumchrus-flemingeri during May, 1998 – 2002; outer nine stations

Upper Mixed Temperature 0.025283

Lower Mixed Temperature 0.421468

Mean Water Column Temperature 0.343750

Potential Energy (Stability) -0.223003

Upper Mixed Salinity -0.757058

Lower Mixed Salinity -0.768888

Mean Salinity -0.783464

Total Redundancy: 63%; Canonical R: 0.79; p = 0.0000027

Neocalanus are negatively correlated to salinity, contrary to expectations for an oceanic species (station outside the ACC)

2001

Distance (km)

0 50 100 150 200

Abu

ndan

ce (

No

m3 )

0

100

200

300

400

500

OTHERSCalanus marshallaeEucalanus bungiiMetridia spp.Neocalanus cristatusN. plumchrus & N. flemingeri

2000

0 50 100 150 2000

100

200

300

400

500

0 5 0 1 0 0 1 5 0 2 0 0

D ista n ce (k m )

-1 0 0

-8 0

-6 0

-4 0

-2 0

0

Dep

th (

m)

0 5 0 1 0 0 1 5 0 2 0 0

-1 0 0

-8 0

-6 0

-4 0

-2 0

0

Dep

th (

m)

30.4

30.8

31.1

31.5

31.8

32.2

32.6

32.9

33.3

33.6

Salinity and Copepod abundance; Seward Line; MayLine is 32.4

Neocalanus populations were low when oceanic water occurs on the shelf, confining brackish water to the ACC

30.4

30.8

31.1

31.5

31.8

32.2

32.6

32.9

33.3

33.6

Salinity and Copepod abundance; Seward Line; MayLine is 32.4

Neocalanus populations were high when low-salinity water is mixed across the shelf to the shelf break or beyond (color key in right panel)

2002

Distance (km)

0 50 100 150 2000

100

200

300

400

500 1998

0 50 100 150 200

Abu

ndan

ce (

No

m3 )

0

100

200

300

400

500

0 5 0 1 0 0 1 5 0 2 0 0

-1 0 0

-8 0

-6 0

-4 0

-2 0

0

Dep

th (

m)

0 5 0 1 0 0 1 5 0 2 0 0 2 5 0

D ista n ce (k m )

-1 0 0

-8 0

-6 0

-4 0

-2 0

0

Dep

th (

m)

March, April, August 1999

29.530

30.531

31.532

32.533

33.534

34.535

0 5 10 15 20 25 30 35 40 45 50

NO3 (um/l)

Sa

lin

ity

(p

su

)

From a poster at ASLO, 2000, by Childers, Whitledge, Stockewll, Weingartner, Danielson, Coyle: Major nutrient distributions in relation to the physical structure of the Gulf of Alaska shelf.

Nitrate is on average positively correlated to salinity

4 0 4 2 4 4 4 6 4 8 5 0 5 2 5 4 5 6 5 8

L a t i t u d e ( d e g r e e s )

-500

-400

-300

-200

-100

Dep

th (

m)

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

Iron concentrations (nmol/kg) from Ocean Station P to the Gulf of Alaska shelf break (Martin et al., 1989)

Iron concentrations in the euphotic zone are very low from ocean station P in the central Gulf of Alaska gyre

northward to the self break off Seward Alaska

Wu, Jingfeng: measured iron on the Seward Line in the upper mixed layer during May, 2004

Iron concentrations (Wu, personal communication)

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

0 50 100 150 200 250

Distance (km)

nmol

kg

-1

Iron concentration in the euphotic zone increased across the shelf from minimal values near the shelf break to maximum values in the Alaska Coastal Current

Summary of observations1) Copepod abundance is strongly and negatively

correlated to salinity.2) Copepod abundance shows little or negative correlation

to water column stability.3) Copepod abundance shows little or no correlation to

upper mixed temperatures.4) When copepod abundance is low, intrusion of oceanic

water onto the shelf constrains the mixing zone to a narrow band near the outer edge of the coastal current.

5) When copepod abundance is high, the mixing zone is spread across the shelf from the coastal current to the shelf break front.

6) Macronutrient concentrations are positively correlated to salinity.

7) Iron concentrations are near threshold detection levels in the mixed layer at the shelf break but about an order of magnitude higher in the Alaska Coastal Current (ACC).

Cross Shelf Distribution of Major Zooplankton Species Relative to Depth Distribution (bar graph insets)

Animals which occur in the upper mixed layer day and night are moved back and forth across the shelf in the wind-mixed layer (Oithona, Neocalanus plumchrus / flemingeri)

Animals residing between the thermocline and permanent halocline tend to be separated on the shelf (Neocalanus cristatus, Eucalanus bungii, Calanus marshallae, Pseudocalanus).

Diurnal vertical migrators, residing below the halocline during the day and above the thermocline at night are apparently avected shoreward in the bottom layer and tend to concentrate on the inner shelf (Metridia spp., Euphausiids)

Mesopelagic animals that occur below the thermocline, even at night are apparently advected shorward in the bottom layer and tend to concentrate in the fjord system of Prince William Sound (Cyphocaris challengeri, Pasaphaea pacifica, Pareuchaeta elongata, pelagic ostracods)

Summary of Distribution

Methods

Introduction: Zooplankton abundance and distribution on the northern Gulf of Alaska shelf are tightly linked to physical processes influencing production and advection of water on and off the shelf. A primary goal of the LTOP project was to document the cross shelf distribution and abundance of major zooplankton taxa relative to water mass movements and to elucidate processes leading to interannual differences is abundance. This poster illustrates cross shelf distribution of major zooplankton species relative to their depth distribution and water mass movements. Contrary to expectation, the abundance of Neocalanus flemingeri, an oceanic species, is negatively correlated to salinity. The abundance-salinity correlation and interannual differences in Neocalanus abundance are related to physical processes, potentially influencing production.Acknowledgments: This research was conducted on the R. V. Alpha Helix. Technical support was provided by the captain, crew and ships technicians (Steve Hartz, Brian Rowe, Dave Aldridge and Dan Mahalck). Aid in sample processing and data entry was provided by Chris Stark, Janet Ballek and Elizabeth Stockmar. The research was multidisciplinary, involving the cooperation of a number of researchers and institutions. They include: Tom Royer, Old Dominion University; Amy Childers, Tom Weingartner, Seth Daniels, Steve Okkonen, Dean Stockwell and Terry Whitledge, University of Alaska Fairbanks. We thank all of the above for their participation in this research effort. The Long Term Observation Program was funded by US GLOBEC award number NA67RJ0147AMD7

Distribution and abundance of zooplankton on the northern Gulf of Alaska shelf relative to water massesKenneth O. Coyle; School of Fisheries and Ocean Science, University of Alaska, Fairbanks Alaska

Interannual Differences in Abundance of Neocalanus flemingeri

Hypothesis: The most likely explanation for the observations is that horizontal mixing between high-nutrient, low-iron oceanic water and high-iron, low-nutrient ACC water promotes elevated primary production in the mixing zone, leading to elevated production of zooplankton grazers.


Month


Mea

n A

bund

anc

e (

No

m3 )

-20

0

20

40

60

80

100

120

140

160

180

199719981999200020012002

Neocalanus, an oceanic species, was more abundant in 1998 and 2002 than in 2000 and 2001 (error bar are 95% confidence intervals)

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