lisa sheffield, ian c. rose, adrian gall, daniel d. roby, david b. irons, & kathy turco
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Seabird Diet and Reproductive Success as Indicators of Ocean Conditions in the Northern Bering Sea. Lisa Sheffield, Ian C. Rose, Adrian Gall, Daniel D. Roby, David B. Irons, & Kathy Turco. 2006 Alaska Marine Science Symposium, Anchorage, AK. The Bering Sea and the “Green Belt”. - PowerPoint PPT PresentationTRANSCRIPT
Lisa Sheffield, Ian C. Rose,
Adrian Gall, Daniel D. Roby,
David B. Irons,
& Kathy Turco
2006 Alaska Marine Science Symposium, Anchorage, AK
Seabird Diet and Reproductive Success as Indicators of Ocean Conditions in the Northern Bering Sea
The Bering Sea and the “Green Belt”
shelf edge
Source: NOAA
The Anadyr CurrentThe Anadyr Current and the “Green Belt”
shelf edge
Source: NOAA
The Northern Bering Sea
• Sea surface temperatures rising
• Sea ice decreasing
• Possible shifts in Anadyr current flow
• Effects on marine life?
A Changing Ecosystem
Sea ice in the Bering Sea
Colonial Seabirds as Indicators
• Marine-dependent /
land-based
• Spatially concentrated & predictable
• Inexpensive (vs. ship time)
Ideal taxon to study ecosystem effects of climate change:
Research Question
• How does seabird diet and reproductive data reflect ocean conditions in the NBS?
Research Question
• How does seabird diet and reproductive data reflect ocean conditions in the NBS?
– What impact might these same conditions have on other upper-trophic level species?
St. Lawrence Island
• 3.6 million breeding seabirds
• 2 Yup’ik villages (Savoonga and Gambell)– Field bases
– Traditional knowledge
• Central location in NBS region
Source: NOAA
Seabird Foraging Guilds
Shallow-divingplanktivore
Deeper-divingplanktivore
Least Auklet:
Crested Auklet:
Murres (2 species):
Pursuit-divingpiscivores
Kittiwake:
Surface-feeding piscivores
Planktivores – The Auklets
• Dominant Bering Sea avian planktivores
• Colonies of >1 million
• ~ 3.2 million nest on SLI
Shallow-divingplanktivore
Deeper-divingplanktivore
Least Auklet:
Crested Auklet:
Auklet Distribution
• Native to deep water (most in Aleutians)
• Only large colonies on the shelf – SLI and Diomede
• Due to Anadyr Current
The Auklets - Diet
Copepods
Euphausiids
Amphipods
Calanus marshallae
Neocalanus cristatus
Neocalanus flemingeri
Thysanoessa raschii Themisto libellula
The Auklets - Diet
Copepods
Euphausiids
Amphipods
Least Auklet diet: Crested Auklet diet :
( Black = Other )
67% Copepods 66%
Euphausiids
2 Genera of Copepods
CopepodsCalanus marshallae
Neocalanus cristatus
Neocalanus flemingeri
Advected by Anadyr Current
Resident on Bering Sea ShelfSmaller, lower mass
Larger, higher mass
2 Genera of Copepods
CopepodsCalanus marshallae
Neocalanus cristatus
Neocalanus flemingeri
Advected by Anadyr Current
Resident on Bering Sea ShelfSmaller, lower mass
Larger, higher mass
Associated with higher reproductivesuccess in both auklets (Gall and Sheffield)
Neocalanus copepods
Copepods
Neocalanus spp.
Hypothesis: Auklets will eat more Neocalanus copepods in years of higher Anadyr Current flow.
Neocalanus copepods
Copepods
Neocalanus spp.
Hypothesis: Auklets will eat more Neocalanus copepods in years of higher Anadyr Current flow.
• Bering Strait current data used as an index (Woodgate et al.)
- >90% correlation
Neocalanus copepods
0
5
10
15
20
25
30
35
40
45
15 20 25 30 35
Copepods
Neocalanus spp.
Hypothesis: Auklets will eat more Neocalanus copepods in years of higher Anadyr Current flow.
Result: Neocalanus cristatus increase exponentially in auklet chick diets as July current flow increases.
July Mean Bering Strait Northward Flow (cm/s)
Per
cen
t B
iom
ass
NE
CR
p = 0.003
R2 = 0.822
CRAU
LEAU
Anadyr Current flow and Auklets
July Anadyr Flow
More Neocalanus cristatus– Collected in August
Source: NOAA
Anadyr Current flow and Auklets
May Anadyr Flow
Earlier LEAU nestingSource: NOAA
p = 0.009
R2 = 0.919
Anadyr Current flow and Auklets
May Anadyr Flow
Earlier LEAU nestingSource: NOAA
What is the mechanism?
p = 0.009
R2 = 0.919
Anadyr Current flow and Auklets
If Anadyr Current (July) = more N. cristatus in chick diets (August),
Does Anadyr Current (May) = more N. cristatus during laying (June)?
Source: NOAA
Anadyr Current flow and Auklets
May Anadyr Flow
Earlier LEAU nestingSource: NOAA
What is the mechanism?
Anadyr Current flow and Auklets
May Anadyr Flow
Early-season prey Early-season prey availability ??? availability ??? ( ( Neocalanus Neocalanus ))
Earlier LEAU nesting
Source: NOAA
Themisto amphipods
Cold-water Arctic species
Amphipods
Themisto libellula
Themisto amphipods
Amphipods
Themisto libellula
Hypothesis: Themisto will be less available as sea surface temperatures increase.
Themisto amphipods
AmphipodsResult: Higher early-summer SST = less Themisto in auklet diets.
0
2
4
6
8
10
12
14
16
18
0 0.2 0.4 0.6 0.8 1May Mean Sea Surface Temperature
Per
cent
T. l
ibel
lula
in C
RA
U d
iets
Hypothesis: Themisto will be less available as sea surface temperatures increase.
Themisto libellula
p = 0.023
R2 = 0.863
Themisto amphipods
AmphipodsResult: Higher early-summer SST = less Themisto in auklet diets.
0
2
4
6
8
10
12
14
16
18
0 0.2 0.4 0.6 0.8 1May Mean Sea Surface Temperature
Per
cent
T. l
ibel
lula
in C
RA
U d
iets
Hypothesis: Themisto will be less available as sea surface temperatures increase.
Themisto libellula
p = 0.023
R2 = 0.863
Will T. libellula decline throughout a warming Bering Sea?
Conclusions• Auklet monitoring:
– NBS ocean conditions affect zooplankton community structure:
• Higher Anadyr current = more Neocalanus cristatus (Monthly scale)• Higher Current = More Neocalanus = Higher auklet success• Higher SST = fewer Themisto amphipods
– Anadyr Current strength affects Least Auklet chronology
• Possibly by advection of early-season Neocalanus
Conclusions• Auklet monitoring:
– NBS ocean conditions affect zooplankton community structure:
• Higher Anadyr current = more Neocalanus cristatus (Monthly scale)• Higher Current = More Neocalanus = Higher auklet success• Higher SST = fewer Themisto amphipods
– Anadyr Current strength affects Least Auklet chronology
• Possibly by advection of early-season Neocalanus
Implications for other marine life?
Implications for other wildlifeP
hoto
sou
rce:
Uni
vers
itite
t I O
slo
Neocalanus
• Auklet prey species are also key prey items for Bowhead Whales (Neocalanus) and Arctic Cod (Themisto).
• Seabirds are the most inexpensive way to study these and other aspects of the NBS ecosystem.
Source: ChartingNature.com
Themisto
Acknowledgements
• Coauthors:– Dan Roby, Lisa Sheffield, Adrian
Gall, David Irons and Kathy Turco
Calvin Akeya, Tim and Roland Alowa, Blake Roberts, Mike Denega, Rebecca Woodgate, Karen Fischer, and everyone in Savoonga, AK!
• Funding:– USFWS, USGS-Oregon Cooperative Fish
and Wildlife Research Unit, Spencer Sealy (UM)
The Savoonga Native Corporation