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Transcript of 1 ECOLOGY of the ANTARCTIC SEA ICE ZONE EASIZ. 2 EASIZ Final Symposium Korcula, Croatia 27 September...
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ECOLOGY of the ANTARCTIC SEA ICE ZONEEASIZ
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EASIZ Final SymposiumKorcula, Croatia27 September 2004
Hugh Ducklow & Robert Daniels
College of William & Mary
Ray Smith, Maria Vernet, Dave Karl, Doug Martinson
Sharon Stammerjohn, Robin Ross, Langdon Quetin, Bill Fraser, Karen Baker, Andy Clarke
Palmer Antarctica LTER
WATER COLUMN PROCESSES
Comparative Plankton Ecology
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ANTARCTIC SEA ICE ZONE
Productivity long-recognized
Sir Alastir Hardy, Great Waters
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1. HOW DO VARIATIONS IN SEA ICE EXTENT & DURATION INFLUENCE WATER COLUMN ECOLOGY & BIOGEOCHEMISTRY?
-- primary production & sedimentation in LTER study region along West Antarctic Peninsula
2. HOW DOES PHYTOPLANKTON COMMUNITY STRUCTURE INFLUENCE BIOGEOCHEMICAL PROCESSES?
-- structure of carbon exchanges in Ross Sea and WAP foodwebs.
3. EMPHASIS ON LARGE-SCALE PROCESSES AND INTERANNUAL VARIATIONS
QUESTIONS
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PALMER, ANTARCTICA Long Term Ecological Research Program (LTER)
• Part of US LTER Network of 26 sites
• 1991 – present
• Regional (200,000 km2) and local sampling
• Focus on sea ice dynamics, water column processes and apex predators
• Physics, remote sensing and ice, microbial biogeochemistry, sedimentation, primary production, krill, penguins
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6PENGUIN COLONIES &FORAGING LOCATIONS
Bathymetry
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1. SEA ICE VARIABILITY AND WATER COLUM PROCESSES
• Sea ice extent, duration and retreat
• Primary production
• Sedimentation – integrator of water column processes – and link to benthos
• Relationships among these processes
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LTER sample grid
Palmer Station
Sediment Trap
~100 stationssurface to bottomgrid sampled every January,1991-2004
LTER Sampling Grid
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Sea Ice in Palmer LTER Study Area
Solid lines: ObservationsDotted lines: 1991-01 mean
Extent (black lines): the area enclosed by the 15% sea ice concentration contour – includes open water in the SIZ.
Area (red): the area covered by sea ice concentrations > 15% within the total extent.
Open water (blue): Extent minus area.
Data from NASA-GSFC SSMI-SSMR Time Series processed by Sharon Stammerjohn and Ray Smith for Palmer LTER
month
km
2
Measuring and characterizing sea ice:
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107753
84627
106750
96765
96733 103164
79780
7421399872
6993278005 153733
Palmer LTER Sea Ice Indices, 1991 - 2002
month
Cov
erag
e, k
m2
Mean extent given for each year. Total area 200,000 km2; max: 1980, 150,000, min: 1989, 42,000
110297
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DA
Y o
f AD
VA
NC
E
DA
Y o
f RE
TR
EA
T
1991-2001 mean at Trap: Day 190 1991-2001 mean at Trap: Day 310
Sea Ice Advance and retreat in LTER grid
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Interannual anomalies in date of ice retreat (WAP)
Symbol in upper center of contour plots is location of sediment trap mooring at 64.5S, 66W
ICE RETREATMean: Day 310
1993: +101994: +201995: +251996: -051997: +201998: -251999: +102000: -052001: -05
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INTERANNUAL ANOMALIES
To describe interannual variability over the decade of sampling:
Standardized anomaly = (Xi – X)/ X
where X is annual mean over the decade.
range –1 to +1 (0 = average)
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INTERANNUAL ANOMALIES
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20 27 34 60 91 121 152 182
17 Jan. 2004
Sediment trap variability, 1993-2003
Image courtesy Helen Quinby
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Year1996 1997
mgC m
-2 d-1
0
20
40
60Sedimentation at 170 meters
Annual sedimentationYear mgC m-2 y-1 %PP1994 1057 1.81995 3467 2.01996 3308 0.91997 402 0.21998 3164 3.01999 3082 6.6 !!2003 1769 1.0
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Palmer annual sedimentation rate
Year
1992 1994 1996 1998 2000 2002 2004
mgC m
-2 y-1
0
500
1000
1500
2000
2500
3000
3500
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CONCEPTUAL MODEL OF SIZ DYNAMICS Ice extent & retreat bloom sedimentation
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1996 1997
μ g liter
-1
0
2
4
6
8
10
1000 km
2
0
50
100
150
200
250
mgC m
-2 d-1
0
20
40
60
Chl -0.08Ice Extent -0.82Flux 94186Mean Ice
PALMER STATION 1996-1997
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PRIMARY PRODUCTION and SEDIMENTATION
YEAR
1990 1992 1994 1996 1998 2000 2002 2004
ANOMALY
-1.0
-0.5
0.0
0.5
1.0
1.5Annual Prim ProdBloom Sedimentation
ICE RETREAT, PRIMARY PRODUCTION AND SEDIMENTATION
SEDIMENTATION and ICE RETREAT
YEAR
1992 1994 1996 1998 2000 2002 2004
TRAP ANOMALY
-1.0
-0.5
0.0
0.5
1.0
RETREAT ANOMALY
-0.10
-0.08
-0.06
-0.04
-0.02
0.00
0.02
0.04
0.06
0.08
0.10
ICE AREA
-0.4 -0.3 -0.2 -0.1 0.0 0.1 0.2 0.3
ICE RETREAT
-0.10
-0.08
-0.06
-0.04
-0.02
0.00
0.02
0.04
0.06
0.08
0.10
ICE RETREAT
-0.12 -0.08 -0.04 0.00 0.04 0.08 0.12
GRID PP
-0.8
-0.4
0.0
0.4
0.8
1.2
ICE AREA AND RETREAT ICE RETREAR & PP
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SEA ICE VARIABILITY AND WATER COLUM PROCESSES
SUMMARY
• +/- 10-25% variations in ice translate to order of magnitude interannual variability in PP and sedimentation
• Sea ice coverage and duration (day of retreat) appear to influence annual variations in production and sedimentation
• 1999: “average” sedimentation but anomalous high relative to PP and ice retreat…a year dominated by salps not krill.
• Need more years!!
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2. COMPARATIVE FOOD WEB STRUCTUREEFFECTS OF PHYTOPLANKTON COMPOSITION
HOW DOES PHYTOPLANKTON COMMUNITY STRUCTURE INFLUENCE BIOGEOCHEMICAL PROCESSES?
COMPARISON OF FOODWEBS IN ROSS SEA POLYNYA AND WEST ANTARCTIC PENINSULA IN JANUARYUSING AN INVERSE APPROACH
Fates of primary production POC and DOC fluxes Foodweb characterization (Legendre &
Rassoulzedegan)
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FOODWEB RECONSTRUCTIONChesapeake Bay
PLANKTON
BENTHOS
FISH
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ROSS SEA POLYNYA STUDY REGION
ROSS SEA POLYNYA STUDIED INTENSIVELY 1994-1999US JGOFS AESOPS PROGRAMROAVERRS PROGRAMITALIAN RESEARCH IN TERRA NOVA BAYPHYTOPLANKTON COMMUNITIES WELL
CHARACTERIZED
Arrigo et al. Science 1999
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ROSS SEA vs WAP
1. ROSS: dominated by Phaeocystis.WAP: diatoms
2. ROSS: grazer biomass low (but few data for polynya) WAP: dominated by krill
3. BACTERIAL PRODUCTION is ~10% of annual NPPand lower during bloom.
4. ROSS: dominated by POC accumulationWAP: ???
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RECONSTRUCTING FOODWEBS: THE PROBLEM
1. MEASUREMENTS ARE NOT ADEQUATE TO FULLY SPECIFY FLOW STRUCTURES IN FOODWEBS. MANY PATHWAYS OR COMPARTMENTS CANNOT BE MEASURED EASILY OR ROUTINELY.
2. WHAT LEVEL OF DETAIL IS NECESSARY? FUNCTIONAL GROUPS? INDIVIDUAL SPECIES?
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WAP 1996:Only 6 out of 46 flows measured.
SmallPhyto
LargePhyto
MicrozooKrill
BacteriaProtoz
AdeliePenguins Myctophids
DOC
Export
Detritus
Measurements Unknown
GPP
Respiration
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AGGREGATED FOOD WEB STRUCTURE
Small phytoplankton*Phaeocystis coloniesDiatomsProtozoan grazersMicrozooplanktonKrill +MesozooplanktonMyctophidsPenguinsBacteriaDetritusDOC
*mostly Phaeocystis unicells < 5 um.
Flows proportional to width of arrows
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THE INVERSE METHOD
1. APPROACH BORROWED FROM GEOPHYSICS (EG, SEISMOLOGY). APPLIED TO FOODWEB RECONSTRUCTION BY VEZINA AND PLATT (1986) – GROWING NUMBER OF STUDIES.
2. USES OBSERVATIONS AND KNOWN BIOLOGICAL CONSTRAINTS (EG, GROWTH & ASSIMILATION EFFICIENCY, BIOMASS-SPECIFIC RESPIRATION) TO GIVE BEST-FIT PATTERNS OF FLOWS IN SPECIFIED FOODWEBS.
3. IN ESSENCE, SOLVING SYSTEMS OF LINEAR BALANCE EQUATIONS. NONSTEADY STATES ARE ADDRESSED.
4. PROVIDES AND OBJECTIVE AND CONSISTENT METHOD FOR FOODWEB RECONSTRUCTION. DIFFERENT ASSUMPTIONS CAN BE TESTED.
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INPUT DATA: ROSS OBSERVATIONS(Primary & Bacterial Production)
mMol C m
-2 d-1
1
10
100
1997 1997
mM
ol C
m-2 d
-1
Primary production
Bacterial production
NPP data courtesy Walker Smith
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INPUT DATA: ROSS OBSERVATIONS(POC and DOC accumulation)
Ross Sea Sargasso Sea0
20
40
60
80
100%
Cu
mu
lati
ve N
PP
0 2
0 40
60
80 100
ROSS SEA SARGASSO SEA
Tota
l D
OC
P
rod
ucti
on
DO
C A
ccu
mu
lati
on
PO
C A
ccu
mu
lati
on
Carbon budgets during 60-70 d spring bloomsCourtesy Craig Carlson
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INPUT DATA: WAP OBSERVATIONS(example)
1996 Foraging1999 Foraging
Observations taken from grid stations within Adelie penguin foraging region determined with remote transmitters on birds.
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STANDING STOCKS
REGION, YEAR
Ross Sea WAP 1996 WAP 1999
mmol C m
-2
0
500
1000
1500
2000
2500
3000
PhytoplanktonZooplankton
INPUT DATA: WAP OBSERVATIONS(example)
Zoop 3
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WAP 1996 GPP = 1200 ROSS SEA 96 GPP = 550
1.26 0.1% 2.16 0.4%
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ProtoZ MicroZ MesoZ DOC Detritus
ProtoZ MicroZ MesoZ DOC Detritus
RESULTS: FATE of PRIMARY PRODUCTION
West Antarctic Peninsula:
Grazer-dominated system
Ross Sea:Detritus-dominated
system
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RESULTS: DOC and POC PRODUCTION
DOC DETWAP
DOC DETROSS
DOC DETN Atlantic
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Small PH
Diatom PHAEO
BACT
PROTO
MICRO
MESOZ
MYCTO
PENG
RESULTS: FOODWEB CLASSIFICATIONafter Legendre and Rassoulzedegan, 1996
DOC
DETR
EXPORT
Key Structuring FlowsIn the foodweb:
1. Large Phytoplankton Production (PT)
Flows normalized to total NPP
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Small PH
Diatom PHAEO
BACT
PROTO
MICRO
MESOZ
MYCTO
PENG
RESULTS: FOODWEB CLASSIFICATION
DOC
DETR
EXPORT
Key Structuring FlowsIn the foodweb:
1. Large Phytoplankton Production
2. Consumption and export via large
grazers & predators (FT)
Flows normalized to total NPP
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Small PH
Diatom PHAEO
BACT
PROTO
MICRO
MESOZ
MYCTO
PENG
RESULTS: FOODWEB CLASSIFICATION
DOC
DETR
EXPORT
Flows normalized to total NPP
Key Structuring FlowsIn the foodweb:
1. Large Phytoplankton Production
2. Consumption and export via large
grazers & predators
3. Ungrazed, sinking phytoplankton (DT)
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Small PH
Diatom PHAEO
BACT
PROTO
MICRO
MESOZ
MYCTO
PENG
RESULTS: FOODWEB CLASSIFICATION
DOC
DETR
EXPORT
Flows normalized to total NPP
Key Structuring FlowsIn the foodweb:
1. Large Phytoplankton Production (PL)
2. Consumption and export via large
grazers & predators (FT)
3. Ungrazed, sinking phytoplankton (DT)
4. Recycled flows via detritus and DOC = 1-(FT + DT)
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Legendre & RassoulzedeganFoodweb models PL/PT RT/PT FT/PT DT/PT
Sinking of ungrazed cells 1.00 0 0 1.00
Herbivorous foodweb 0.80 0.30 0.60 0.10
Multivorous foodweb 0.35 0.60 0.30 0.10
Microbial foodweb 0.10 0.80 0.20 0
Microbial Loop 0 1.00 0 0
INVERSE RESULTS
North Atlantic Bloom 0.50 0.78 0.04 0.18
WAP 1996 0.67 0.69 0.19 0.11
ROSS SEA 1996 0.54 0.47 0.02 0.50
RESULTS: FOODWEB CLASSIFICATION
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COMPARATIVE FOOD WEB STRUCTURESUMMARY
1. PLAUSIBLE FOODWEBS, CONSISTENT WITH OBSERVATIONS, CAN BE RECOVERED FOR BOTH AREAS.
2. BOTH REGIONS DOMINATED BY LARGE PHYTOPLANKTON
BUT TAXON DIFFERENCES LEAD TO CONTRASTS IN GRAZER ABUNDANCE AND IMPACTS
3. WAP: GRAZER-DOMINATED SYSTEM ROSS: DETRITAL-DOMINATED
4. MOST DETRITAL FLOW ORIGINATES FROM UNGRAZED PHYTOPLANKTON
5. FOODWEB STRUCTURE DOMINATED BY LARGE PHYTOPLANKTON BUT TEND TOWARDS MICROBIAL FOODWEB STRUCTURE – EVEN WITH LOW BP AND DOC.
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FINAL THOUGHTS
1. IMPORTANCE OF SEA ICE IN STRUCTURING SYSTEMS
2. NEED TO WORK LONG TERM AT REGIONAL SCALES
3. NEED FOR MODELS TO INTEGRATE SPARSE OBSERVATIONS
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ACKNOWLEDGEMENTS and THANKS
Palmer LTER Colleagues
US JGOFS Colleagues: Walker Smith & Bob Anderson (AESOPS)
ROAVERRS Project: Jack DiTullio et al.
George Jackson & Tammi Richardson (TAMU – inverse models)
Helen Quinby, Joann Kelly and many others for lab help
NSF-OPP
Andy Clarke and EASIZ, for the invitation
All of you, for your attention
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Inshore, local area samplingTwice per week, October - April
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Palmer annual mean temperature, 1979 - 2003
degrees Celsius-5
-4
-3
-2
-1
0
Palmer annual mean ice extent, 1979 - 2003
Year
1980 1985 1990 1995 2000
103 kilometers
20406080
100120140160
PALMER MEAN ANNUAL TEMPERATURE 1979-2003
PALMER MEAN SEA ICE EXTENT 1979-2003
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ICE ANOMALY
-0.3 -0.2 -0.1 0.0 0.1 0.2 0.3
PP ANOMALY
-1.2
-0.8
-0.4
0.0
0.4
0.8
1.2
YEAR
1990 1992 1994 1996 1998 2000 2002 2004
PP ANOMALY
-0.3
-0.2
-0.1
0.0
0.1
0.2
0.3
ICE ANOMALY
-1.2
-0.8
-0.4
0.0
0.4
0.8
1.2
Open water in ice margin and primary production
More open ice margin, less PP
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Sea Ice Area and Day of Retreatlarger area – later retreat