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)
0
20
40
60
80
100
120
140
PA
R (
mo
l q
ua
nta
m-2
d-1
)
0
10
20
30
40
50
(0 -
125 m
)(1
50 m
)
MLD PAR