Meridional Variations in Dissolved and Particulate Matter Concentrations and Stoichiometriesin the Tropical and Subtropical Pacific Ocean

Eric M. Grabowski, Karin M. Björkman, Matthew J. Church, Tara M. Clemente, Susan E. Curless, J. Ken Doggett, Lance A. Fujieki, Thomas K. Gregory,Adriana E. Harlan, *Ricardo M. Letelier, Claire Mahaffey, Daniel W. Sadler, Blake V. W. Watkins & David M. Karl

Abstract Objectives

Ecological Provinces Sampled

South Pacific Subtropical Gyre Province SPSG 35o S - 5o S

Pacific Equatorial Divergence Province PEQD 5o S - 5o N

North Pacific Equatorial Countercurrent Province PNEC 5o N - 10o N

North Pacific Tropical Gyre Province NPTG 10o N - 34o N

Regionalize Time-series Observations at Station ALOHA

Evaluate Spatial Gradients in Dissolved and Particulate Matter Elemental Composition

Assess Relationships Between Plankton Community Structure and Nutrient Availability

Acknowledgements

SPSG

PEQD

PNEC

NPTG

University of Hawaii, Department of Oceanography, Honolulu, HI 96822

Surface Ocean Concentrations, Distributions and Elemental Stochiometries of Particulate Organic Matter Between American Samoa and Hawaii (Station ALOHA)

Vertical Distributions of Pigmented Planktonic Microorganisms in the North and South Pacific Ocean

Vertical Distributions of Temperature, Nutrients and Chlorophyll a in the North and South Pacific Ocean

Depth profiles of chlorophyll a (green), PO43- (red) and temperature (blue) at selected stations in the

ecological provinces sampled along the cruise transect. The dotted line indicates the mixed-layer depth based on a 0.125 unit change in potential density. A) SPSG (12.69o S), B) PEQD (0.628o N), C) PNEC (6.00o N), D) NPTG (15.847o N), E) Station ALOHA (May 2005) located in the NPTG (22.75o N)

North and South Gyres were characterized by subsurface chlorophyll maximum while equatorial re-gions demonstrated more even distributions of chorophyll a in the upper ocean

Vertical position of deep chlorophyll maximum tended to be elevated in the SPSG relative to NPTG

Concentration of PO43- were more than an order of magnitude greater in the Equatorial regions than

in the NPTG, while PO43- concentrations in the SPSG were approximately 2-fold greater than the NPTG

MODIS satelite derived sea surface chlorophyll distributions and concentrations along cruise transect from American Samoa to Hawaii in April - May 2005

Flow cytometric determinations of Prochlorococcus (blue), Synechococcus (red), and picoeukaryotes (green) at selected stations in ecological provinces along a cruise transect from American Samoa to Hawaii in May 2005. The dotted line indicates the mixed-layer depth based on a 0.125 unit change in potential density. A) SPSG (12.69o S), B) PEQD (0.628o N), C) PNEC (6.00o N), D) NPTG (15.847o N), E) Station ALOHA (May 2005) located in the NPTG (22.75o N)

SPSG and NPTG upper ocean concentrations of Synechococcus and picoeukaryotes were generally similar while Synechococcus and picoeukaryotes were 5 to 10 fold greater in the equatorial region than in the SPSG and NPTG

Cell abundances of Prochlorococcus were greater in the PNEC than in the SPSG, PEQD and NPTG

Longitude

Lati

tud

e

American Samoa to Hawaii

*Oregon State University, College of Oceanic and Atmospheric Sciences, Corvallis, OR 97331

Latitudinal distribution of surface water chlorophyll a, b and c. Stars represent surface water concentrations of chlorophyll a, b and c at Station ALOHA in May 2005.

Surface water concentrations of PO43- and silicate. Stars represent surface water PO4

3- and Si concentrations at Station ALOHA in May 2005.

Partial pressure of surface water (blue) and mean atmosphere (red) pCO2. Star represents sur-face pCO2 at Station ALOHA in May 2005.

A)

B)

C)

Longhurst1998

StationALOHA

Our participation in this cruise of opportunity was made possible by the School of Ocean and Earth Sci-ence and Technology. In particular, Dr. Brian Taylor provided logistical support for our sampling and the State of Hawaii provided ship time. The National Science Foundation and the Gordon and Betty Moore Foundation have enabled our efforts to spatially and temporally characterize the North Pacific Ocean. The efforts of the officers, crew and OTG science group of the R/V Kilo Moana got us home safely.

Meridional distributions of near-surface (5-15m) concentrations of Particulate Carbon (A), Particulate Nitrogen (B), and Particulate Phosphorus (C). Panels D, E and F represent the mean (± 1 StDev) of particulate matter concentration binned by province. Panels G, H and I represent mean (± 1 StDev) of particulate matter elemental ratios within each province. Stars represent concentrations and ratios sampled at Station ALOHA in May 2005.

The partitioning of bioessential elements including carbon (C), nitrogen (N), and phosphorus (P) between organic and inorganic forms and among particulate and dissolved phases depends in part on the activities of planktonic microorganisms. In an effort to regionalize time-series obser-vations at Station ALOHA, the field site for the Hawaii Ocean Time-series (HOT) program, surface water concentrations of inorganic nutrients (nitrate + nitrite [N+N], and PO4

3- ) and organic nutri-ents (dissolved organic carbon, dissolved organic nitrogen and dissolved organic phosphorus) were sampled along a meridional transect from American Samoa to Honolulu, Hawaii in May 2005. This cruise provided an opportunity to evaluate spatial gradients in dissolved and particu-late matter elemental composition between several open ocean biogeochemical provinces in-cluding both the North and South Pacific subtropical gyres and equatorial waters. The transition from the South Pacific Subtropical Gyre into equatorial waters was accompanied by sharp in-crease in the concentrations of inorganic nutrients and corresponding changes in dissolved and particulate matter concentrations and stoichiometries. In particular, surface water concentrations of PO4

3- increased approximately 4-fold between 3o S and 3o N, while particulate C, N and P con-centrations increased approximately 2-fold in the same region. In general, particulate matter C:N:P ratios varied widely along the transect, with particulate matter pools enriched in both C and N relative to P found in both the oligotrophic South and North Pacific subtropical gyres. Flow cytometric analyses of picoplankton community populations revealed relatively constant cell abundances of Prochlorococcus with latitude, while both Synechococcus and picoeukaryote abun-dances increased more than 5-fold in the equatorial waters. Alterations in plankton community structure stemming from meridional variations in nutrient availability likely dictate the resulting particulate matter stoichiometries, and ultimately constrain the composition of organic matter exported to the deep sea.

Biogeochemical & Ecological Analysis of Complex Habitats - Between American Samoa & Hawaii (BEACH-BASH)

MarineMicrobiologyInitiative

0 0.2 0.4 0.6 0.8 1 1.2PO4

3- (µmol/l)

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4Chloropyll a (µg/l)

12 14 16 18 20 22 24 26 28 30200

150

100

50

0

Temperature (Deg C)

Pre

ssur

e (d

bars

)

SPSG

0 0.2 0.4 0.6 0.8 1 1.2µmol/l)

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4Chloropyll a (µg/l)

12 14 16 18 20 22 24 26 28 30200

150

100

50

0

Temperature (Deg C)

Pre

ssur

e (d

bars

)

PEQD

PO43- (

0 0.2 0.4 0.6 0.8 1 1.2µmol/l)

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4Chloropyll a (µg/l)

12 14 16 18 20 22 24 26 28 30200

150

100

50

0

Temperature (Deg C)

Pre

ssur

e (d

bars

)

PNEC

PO43- (

0 0.2 0.4 0.6 0.8 1 1.2µmol/l)

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4Chloropyll a (µg/l)

12 14 16 18 20 22 24 26 28 30200

150

100

50

0

Temperature (Deg C)

Pre

ssur

e (d

bars

)

NPTG

PO43- (

101 102 103 104 105200

150

100

50

0

Cell abundance (#/ml)

Pre

ssur

e (d

bars

)

SPSGProSynEuk

101 102 103 104 105200

150

100

50

0

Cell abundance (#/ml)

Pre

ssur

e (d

bars

)

PEQDProSynEuk

101 102 103 104 105200

150

100

50

0

Cell abundance (#/ml)

Pre

ssur

e (d

bars

)

PNECProSynEuk

101 102 103 104 105200

150

100

50

0

Cell abundance (#/ml)

Pre

ssur

e (d

bars

)

NPTGProSynEuk

0 0.2 0.4 0.6 0.8 1 1.2µmol/l)

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4Chloropyll a (µg/l)

12 14 16 18 20 22 24 26 28 30200

150

100

50

0

Temperature (Deg C)

Pre

ssur

e (d

bars

)

Stn. ALOHA

PO43- (

101 102 103 104 105200

150

100

50

0

Cell abundance (#/ml)

Pre

ssur

e (d

bars

)

Stn. ALOHAProSynEuk

Par

ticul

ate

Car

bon

(µm

ol/l)

SPSG PEQD PNEC NPTG ALOHA1.5

2

2.5

3

3.5

4

4.5

Par

ticul

ate

Nitr

ogen

(µm

ol/l)

SPSG PEQD PNEC NPTG ALOHA0.2

0.3

0.4

0.5

0.6

0.7

Par

ticul

ate

Pho

spho

rus

(µm

ol/l)

SPSG PEQD PNEC NPTG ALOHA0.005

0.01

0.015

0.02

Par

ticul

ate

Car

bon

(µm

ol/l)

15 S 10 S 5 S 0 N 5 N 10 N 15 N 20 N 25 N1.5

2

2.5

3

3.5

4

4.5

PC

:PN

(mol

:mol

)

SPSG PEQD PNEC NPTG ALOHA5

6

7

8

9

Par

ticul

ate

Nitr

ogen

(µm

ol/l)

15 S 10 S 5 S 0 N 5 N 10 N 15 N 20 N 25 N0.2

0.3

0.4

0.5

0.6

0.7

PN

:PP

(mol

:mol

)

SPSG PEQD PNEC NPTG ALOHA 20

25

30

35

40

45

50

Par

ticul

ate

Pho

spho

rus

(µm

ol/l)

15 S 10 S 5 S 0 N 5 N 10 N 15 N 20 N 25 N0.005

0.01

0.015

0.02

PC

:PP

(mol

:mol

) SPSG PEQD PNEC NPTG ALOHA

150

200

250

300

350

Sea

Surf

ace

Ch

loro

ph

yll (

g

/l)

µ

pCO

2 (µa

tm)

Atmosphere

15 S 10 S 5 S 0 N 5 N 10 N 15 N 20 N 25 N340

360

380

400

420

440

460

Meridional Distributions of Chlorophyll a, b,c, PO43-, Siand pCO2 Between American Samoa and Hawaii

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.1

Chl

orop

hyll

b &

c ( µ

g/l)

Chl

orop

hyll

a (µ

g/l)

Chl bChl c

15 S 10 S 5 S 0 N 5 N 10 N 15 N 20 N 25 N0

0.05

0.1

0.15

0.2

0.25

0

0.5

1

1.5

2

2.5

3

Si (

µmol

/l)

PO

43− (µ

mol

/l)

15 S 10 S 5 S 0 N 5 N 10 N 15 N 20 N 25 N0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

Chl a A

B

C

A B C D E

A B CD E

A

B

C

D

E

F

G

H

I

Poster#OS36C-06