Diatom Dynamics in the North Pacific Subtropical Gyre...

TEMPLATE DESIGN © 2008

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Aula-group

Chaet-gro

up

Cylin-gro

up

Pnitz-gro

up

Sella-gro

up

Gen

e c

op

ies m

-2

107

108

109

1010

1011

Edge Jul 2008 HOT Jun 2008 HOT Aug 2008

LLN LLSi

NO

3-

+ N

O2-

(um

ol

m-2

)

0

5000

10000

15000

20000

25000

30000

Sil

icic

ac

id (

mm

ol

m-2

)

0

100

200

300

400

Edge Jul 2008 HOT Jun 2008 HOT Aug 2008

Collect and preserve diatom samples

Time-series:

Monthly cruises to Station ALOHA (2007-2009)

Sampling of upper ocean (0-175 m) suspended

cells and sinking particulate material (150 m)

DNA, RNA and slides for microscopic identification

of diatoms

Spatial variation:

Gyre-scale (BRZ cruise), Mesoscale (CMORE

summer cruises)

Analyses of diatom community structure in the

center and along the Northern Edge of the gyre

Identification and quantification of diatoms

Molecular-tech

DNA fingerprint

Microscopy Morphology

Cylindrotheca sp.

rbcL gene – Large subunit of

RuBisCOATTAACTCACAACCATTCATGCGTTGGAGAGAA

CGTTTCTTAAACTGTATGGAAGGTATTAACCGT

GCATCTGCTGCAACTGGTGAAGTTAAAGGTTC

ATACTTAAACGTTACAGGCGCAACGATGGAAG

AAGTTTACAAACGTTCAGAGTACGCTAAAGAA

GTAGGTTCTATCGTTATTATGATCGATTTAGTTAT

GGGTTATACAGCAATTCAAAGTATTGCTTTATG

GGCTCGTGAAAATGATATGCTTTTACATTTACA

CCGTGCTGGTAACTCAACTTACGCACGTCAAA

AAAATCACGGTATTAATTTCCGTGTAATTTGTAA

ATGGATGCGTATGTCTGGTGTAGATCATATCCA

CGCTGGTACAGTTGTAGGTAAATTAGAAGGTGA

TCCTTTAATGATTAAAGGTTTCTACGATACTTTA

CGTTTAACTGCTTTAGATGTTAACTTACCTTATG

GTTTATTCTTCGAAATG

BLAST result in GenBank:

Cylindrotheca closterium

(DQ019445) 95% similarity

Diatom Dynamics in the North Pacific Subtropical Gyre (NPSG)

Binglin Li and Matthew Church

Department of Oceanography, University of Hawaii, 1000 Pope Rd, Honolulu HI 96822

Abstract

Introduction

Phylogenetic relationships among diatom rbcL

sequences obtained from the NPSG

Time-series measurements of particulate carbon

and particulate silica export based on sediment

traps (150 m) at Station ALOHA.

Diatoms generally comprise minor components

of plankton biomass in oligotrophic open ocean

ecosystems. However various lines of evidence

suggest diatoms are major contributors to

annually recurring phytoplankton blooms in the

NPSG. Moreover, these diatom-dominated

blooms play central roles in the exchange of

material between the upper ocean and the deep

sea at Station ALOHA (22o45’ N, 158oW). Our

understanding of diatom bloom dynamics is

partly hampered by a lack of knowledge on

temporal variability in diatom community

structure in this ecosystem. In this study, we

utilized both microscopic- and molecular-based

technologies to investigate temporal and spatial

dynamics in diatom assemblages in the NPSG.

Group specific quantitative PCR primers targeting

diatom rbcL genes were designed and employed

to examine time and space dependent changes in

the abundances of several major diatom genera.

In addition, we evaluated the contributions of

several groups of diatoms to particulate matter

export at Station ALOHA.

Objectives

Approaches

Results Results

Acknowledgements

Conclusions

Molecular approach:

PCR – clone library

Design diatom specific rbcL gene PCR primers

QPCR

Group specific rbcL QPCR primers that target major

diatom genera

Characterization of temporal and spatial

dynamics in diatom population structure

Examination of the contributions of the

specific members of the diatom assemblage to

carbon production and export

Identification of the processes controlling

diatom productivity

Vertical distribution of specific diatom groups

Spatial distribution: center vs northern edge of

the NPSG

Time series: Suspended Cells vs Sinking Flux

at Station ALOHA

CMORE provided funding and shipboard

support that made this study possible.

The great support of the HOT team, the crew

of RV Kilo Moana.

Dr. David Karl

The vertical distribution of diatoms has a strong

seasonal variation.

Abundance of specific diatom groups were not

substantially different between the northern edge and

the center of the NPSG, although nitrate + nitrite and

silicic acid concentrations were substantially higher

in the northern edge.

The export of specific diatoms appeared temporally

coincide with their abundances in the upper ocean.

The flux of diatom rbcL genes appeared inversely

related to the depth of the mixed layer at Station

ALOHA.

Satellite observations:

Satellite remote sensing of

surface ocean chlorophyll

concentrations in the NPSG

indicate recurring

summertime phytoplankton

blooms.

Direct observations:

In 12 of the past 20 years

(1989-2008) shipboard

measurements indicate

diatoms comprise important

components of these blooms.

(From Angel White)

Spring Summer Fall Winter

PC

flu

x (

mg

m-2

d-1

)

20

25

30

35

40

PS

i fl

ux (

mg

m-2

d-1

)

0

2

4

6

8

10PC

PSi

QPCR primers

Aulacoseira-group

Sellaphora-group

Chaetoceros-group

Pseudonitzschia-

group

Cylindrotheca-group

Jan 2008 Jul 2008May 2008 Oct 2008

PSi concentrations at Station ALOHA

PSi (nM)

0 10 20 30 40

De

pth

(m

)

0

20

40

60

80

100

120

140

160

Pseudonitzschia-group rbcL gene at Station ALOHA

Gene copies L-1 104 105 106

De

pth

(m

)

0

20

40

60

80

100

120

140

160

Jan 2008 Jul 2008May 2008 Oct 2008

Centric Pennate

Rb

cL

gen

e c

op

ies m

-2

108

109

1010

1011

Pseudonitzschia-group

Sellaphora-group

Oct

07

Nov

07

Dec

07

Jan 0

8

Feb 0

8

May

08

Jun 0

8

Jul 0

8

Aug 0

8

Oct

08

Nov

08

Jan 0

9

Rb

cL

gen

e c

op

ies m

-2 d

-1

104

105

106

107

108

Pseudonitzschia-group flux

Sellaphora-group flux

ML

D (

m)

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PA

R (

mo

l q

ua

nta

m-2

d-1

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0

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(0 -

125 m

)(1

50 m

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MLD PAR