Climate induced shifts in the phytoplankton community biomass
and community structure along the West Antarctica Peninsula
1
Schofield ,
1
Kahl ,
1
Saba ,
2
Finkel ,
2
Irwin
Oscar
Alex
Grace
Zoe
Andrew
Mark Moline3, Maria Vernet4, Barbara Prezelin5, and Hugh Ducklow6
1: Rutgers University, 2: Mount Allison University, 3: University of Delaware, 4: Scripps, 5: UCSB, and 6: MBL
Time Series of Ship Spatial Grid (Phytoplankton Communities)
SSS
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The Palmer LTER sampling consists of two major
research strategies. The first component of the PAL
LTER is the biweekly sampling conducted at Palmer
Station on Anvers Island (indicated by the red circle)
for the spring and summer seasons (October
through mid-March).
The sampling at Palmer
consists of time series measurements at several
fixed stations. This sampling in time is
complemented with a ship sampling grid conducted
each January along the WAP, spanning from the
waters near Palmer Station to the waters South of
Marguerite Bay. For this study we emphasize the
sampling of the phytoplankton communities with a
focus on the HPLC sampling of phytoplankton
pigments that are used as chemotaxonomic
markers for the major phytoplankton taxa.
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Variability in ship sea surface temperature (SST),
sea surface salinity (SSS), diatoms (Fuco/chl a),
cryptophytes (Allo/chl a) is shown on the left over
several years. The variability in the parameters
show strong inshore and offshore gradients as well
as strong north to south gradients. Generally the
inshore waters of the LTER grid is cooler in the
summer months by over 1 degree compared to
offshore waters. Similarly there is a strong inshore
offshore gradient in sea surface salinity with lower
salinity found nearshore, presumably reflecting the
melting ice. Generally the diatoms and cryptophytes
are segregated in space and time. The spatial
variability in the two phytoplankton taxa show a
great deal of interannual variability. Both taxa are
found in the north and south as well as in the
nearshore and offshore waters. There is no
apparent correlation between the phytoplankton
community structure and the sea surface
temperature and salinity.
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SST
.9
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The West Antarctic Peninsula (WAP) is experiencing the fastest rates of regional climate change on
Earth. The impact of these changes on the ecosystem is an open question. It has been documented
the WAP has a productive ecosystem, however there is evidence that over the past 30 years, the
magnitude of WAP phytoplankton blooms have decreased by 12%. Declines in WAP phytoplankton
appear to have been accompanied by shifts in the phytoplankton community structure based on
satellite data that suggest algal community structure appears to have shifted from large (50-100
microns) to small cells (5-10 microns). Declines in phytoplankton biomass and community
structure have been hypothesized to underlie shifts in the zooplankton and apex predators in
the WAP food webs. For this poster, using LTER time series we assess phytoplankton
communities dynamics that may underlie the suggested shifts in the satellite imagery.
−0
−0 .6
.7
Introduction
●
●
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Phytoplankton Communities in Hydrologic Space
Palmer Station Data
3
Time Series at Palmer Station (Phytoplankton Communities)
Ship Station Data
3
Temperature
1
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33
30
34
31
Different cryptophyte species
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Dinoflagellate
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Predator
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Other
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−70
−65
0.
0.
12 1 4
0.
2
0.
18
0.
16
−67
●
●
0.14
●
●
●
0.12
●
●
0.020
●
●
●
●
●
●
●
●
●
●
●
●
●
−75
●
●
●
●
●
●
●
3
●
5
0.02
●
0.16
●
●
●
●
●
●
●
−68
●
●
●
●
●
●
●
●
●
●
−69
●
●
0.2
0.18
●
●
●
0.05
●
●
●
●
−68
●
0.3
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
0.025
●
●
0.3
●
●
●
●
●
●
−67
●
●
●
●
●
●
−67
●
●
●
●
●
●
●
0.10
●
0.030
0.
1
●
●
●
●
●
●
0.
02
●
−66
●
●
●
●
0.05
0.4
●
●
●
●
●
●
Y
●
−66
Y
●
●
0.15
●
●
0.
1
0. 4
−66
●
●
●
●
0.5
●
●
0 .1
●
●
●
●
0.0
3
0.6
●
●
●
●
−65
●
●
●
●
●
−66
●
Y
0.2
●
●
−65
−65
0 .4
●
●
●
0.15
●
●
0. 6
22735
0. 0
0.5
2850 12.5
●
●
●
0.4
Y
2.1
●
●
●
●
●
●
●
●
●
●
●
●
0 .7
Total
486
2.4
0.6
0.8
●
−67
Others
555
32
●
●
●
●
●
●
●
●
0.4
●
−68
Dinos
7360
●
●
●
●
●
0.6
●
●
0.20
●
●
●
●
0.1
Diatoms
51
0.20
0.8
●
0.05
Cryptophytes 11484
%
FlagStraight
0.15
Count
Larger category
Flagellate all
Flagellate all
Flagellate all
Diatom all
Diatom all
Diatom all
Diatom all
Flagellate all
Flagellate all
Flagellate all
Discard
Flagellate all
Flagellate all
Flagellate all
Discard
Other
Flagellate all
Discard
Flagellate all
Other
Flagellate all
Other
Discard
Discard
Discard
Diatom all
Flagellate all
Flagellate all
Other
Other
Discard
Discard
CryptF
5
Group
Classified as
Cryptophyte A
Cryptophyte F
Cryptophyte H
Diatom
Diatom (charisma c)
Diatom (fuzzy)
Diatom (poten al)
Dot flagellate
Dot flagellate 2
Flagellate straight
Fuzzy
Gymnodinium 1
Gymnodinium 2
Gyrodinium
Junk
LRT
Nanoflagellate
Pigment
Prasinophyte
Telonema spp.
Torodinium spp
Unknown
Air bubble
Bead
Ciliate
Corethron spp.
Dinoflagellate
Gonyaulacaceae
Phaeocys s spp. (cells)
Phaeocys s spp. (colony)
Spines
Tin nnid
CryptAH
0.0
Classification
summary
Corethron criophilum
34
To assess the relative distribution of cryptophytes and diatoms for the Palmer and ship data sets we have plotted the
data in temperature and salinity space. The blue circles represent diatom pigments and the green circles indicate the
cryptophyte pigments. The size of the circles indicates the pigment concentrations. For Palmer Station, the
cryptophytes and diatoms segregate in temperature and salinity space. Cryptophytes are generally found in colder
and lower salinity water. At Palmer this is largely associated with ice water melt. This association with the
cryptophytes with these water masses is robust over the 20 year data set, however the driver of this association
remains an open question. In contrast, the ship data does not show the same segregation in temperature salinity
space. For the ship surveys, the crypotophytes are distributed across the full temperature and salinity ranges. What
might underlie this variable distribution?
Cryptophytes
100mm
Thalassiosira antarctica
33
Salinity
salinity
Diatoms and Cryptophytes Relationships
32
Salinity
Flag. predator
The net result was of the
seasonal
phytoplankton
bloom dynamics was the
complete separation of the
cryptophytes and diatoms.
When cryptophytes bloom,
the diatoms are not
present and vice versa.
This shift in phytoplankton
communities represents a
major
shift
in
the
phytoplankton size spectra.
Cryptophytes
in
these
waters are typically 5-10x
smaller in size then the
dominant
blooming
diatoms.
1
0.1
Time-series measurements within the
years for the two dominant phytoplankton
taxa generally show strong segregation in
time. The cryptophytes (indicated by the
marker pigment alloxanthin, green), were
found to bloom after the seasonal retreat
in sea ice (indicated by the black arrow),
The diatoms (indicated by the marker
pigment fucoxanthin, blue). The diatoms
show major blooms throughout the year
that are timed prior to and after the
seasonal sea ice retreat.
2
−69
Chlorophyll a
Time-series measurements from Palmer
Station show high inter-annual variability
in chlorophyll a (bottom right panel).
Using ChemTax we calculated the % of
the total chlorophyll a associated with the
major phytoplankton taxa. Diatoms were
the dominant taxa present (panel A). The
next most abundant phytoplankton were
the
cryptophytes.
Mixed
flagellate
communities and prasinophytes rarely
dominated the communities. Type-4
haptophytes (Phaoecystis) was the third
most
abundant
taxa
at
Palmer,
consistently accounting for 20% of the
communities but showing no interannual
variability.
Temperature
2
●
●
●
−75
−70
−65
●
0.10
●
●
●
●
−75
−70
−65
During the 2012 field season we incorporated a video sorting technology (FlowCam) to classify the different
phytoplankton species. Above we show the data collected using the new technology. Consistent with the historical
pigment data, the diatoms and cryptophytes were segregated in space and time (data not shown). The new
technologies provide species information and showed that several different species of cryptophytes were present and
differentially distributed across the WAP. Based on this view, our current hypothesis is the differential segregation of
cryptophytes between the between the Palmer station and Ship in temperature and salinity space, reflects the relative
distribution of these different species cryptophytes. This suggests better incorporation of species identification is a key
need to be incorporated into the regional sampling.
Palmer Cryptophytes --> 8 ± 2mm
SEM Micrographs fromMcMinn and Hodgson 1993
10mm
Cryptomonas cryophila
Acknowledgments: This time series represents a large community effort and we gratefully acknowledge our partners over the
lifetime of the program. We also acknowledge the generous funding support of the NASA Biodiversity program and of the
Gordon and Betty Moore Foundation.
Conclusions
l Diatoms and cryptophytes are the major phytoplankton taxa present within the Palmer LTER sampling grid
l Diatoms and cryptophytes are segregated in space and time
l The segregation of diatoms and cryptophytes in temperature and salinity space is variable between Palmer station
and regional ship surveys. These differences likely reflect species levels responses which suggests important needs
to augment the existing Palmer LTER sampling.