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Lisa Sheffield, Ian C. Rose, Adrian Gall, Daniel D. Roby, David B. Irons, & Kathy Turco

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”.

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Lisa Sheffield, Ian C. Rose, Adrian Gall, Daniel D. Roby, David B. Irons, & Kathy Turco

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  1. 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

  2. The Bering Sea and the “Green Belt” shelf edge Source: NOAA

  3. The Anadyr Currentand the “Green Belt” shelf edge Source: NOAA

  4. The Northern Bering Sea A Changing Ecosystem • Sea surface temperatures rising • Sea ice decreasing • Possible shifts in Anadyr current flow • Effects on marine life? Sea ice in the Bering Sea

  5. Colonial Seabirds as Indicators Ideal taxon to study ecosystem effects of climate change: • Marine-dependent / land-based • Spatially concentrated & predictable • Inexpensive (vs. ship time)

  6. Research Question • How does seabird diet and reproductive data reflect ocean conditions in the NBS?

  7. 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?

  8. 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

  9. Seabird Foraging Guilds Least Auklet: Murres (2 species): Shallow-diving planktivore Pursuit-diving piscivores Crested Auklet: Kittiwake: Surface-feeding piscivores Deeper-diving planktivore

  10. Dominant Bering Sea avian planktivores Colonies of >1 million ~ 3.2 million nest on SLI Planktivores – The Auklets Least Auklet: Shallow-diving planktivore Crested Auklet: Deeper-diving planktivore

  11. Auklet Distribution • Native to deep water • (most in Aleutians) • Only large colonies • on the shelf – • SLI and Diomede • Due to Anadyr Current

  12. The Auklets - Diet Copepods Euphausiids Amphipods Thysanoessa raschii Themisto libellula Calanus marshallae Neocalanus cristatus Neocalanus flemingeri

  13. The Auklets - Diet Copepods Euphausiids Amphipods Crested Auklet diet : Least Auklet diet: 67% Copepods 66% Euphausiids ( Black = Other )

  14. 2 Genera of Copepods Calanus marshallae Copepods Resident on Bering Sea Shelf Smaller, lower mass Neocalanus cristatus Neocalanus flemingeri Advected by Anadyr Current Larger, higher mass

  15. 2 Genera of Copepods Calanus marshallae Copepods Resident on Bering Sea Shelf Smaller, lower mass Neocalanus cristatus Neocalanus flemingeri Advected by Anadyr Current Larger, higher mass Associated with higher reproductive success in both auklets (Gall and Sheffield)

  16. Neocalanus copepods Hypothesis: Auklets will eat more Neocalanus copepods in years of higher Anadyr Current flow. Copepods Neocalanus spp.

  17. Neocalanus copepods Hypothesis: Auklets will eat more Neocalanus copepods in years of higher Anadyr Current flow. Copepods • Bering Strait current data used as an index • (Woodgate et al.) • - >90% correlation Neocalanus spp.

  18. Neocalanus copepods Hypothesis: Auklets will eat more Neocalanus copepods in years of higher Anadyr Current flow. Copepods Result:Neocalanuscristatus increase exponentially in auklet chick diets as July current flow increases. Neocalanus spp. CRAU p = 0.003 Percent Biomass NECR R2 = 0.822 LEAU July Mean Bering Strait Northward Flow (cm/s)

  19. July Anadyr Flow More Neocalanus cristatus Collected in August Anadyr Current flow and Auklets Source: NOAA

  20. May Anadyr Flow Earlier LEAU nesting Anadyr Current flow and Auklets Source: NOAA p = 0.009 R2 = 0.919

  21. May Anadyr Flow Earlier LEAU nesting Anadyr Current flow and Auklets Source: NOAA p = 0.009 R2 = 0.919 What is the mechanism?

  22. If Anadyr Current (July) = more N. cristatus in chick diets (August), Does Anadyr Current (May) = more N. cristatus during laying (June)? Anadyr Current flow and Auklets Source: NOAA

  23. May Anadyr Flow Earlier LEAU nesting Anadyr Current flow and Auklets Source: NOAA What is the mechanism?

  24. May Anadyr Flow Early-season prey availability ??? ( Neocalanus ) Earlier LEAU nesting Anadyr Current flow and Auklets Source: NOAA

  25. Themisto amphipods Themisto libellula Cold-water Arctic species Amphipods

  26. Themisto amphipods Hypothesis:Themisto will be less available as sea surface temperatures increase. Amphipods Themisto libellula

  27. Themisto amphipods Hypothesis:Themisto will be less available as sea surface temperatures increase. Amphipods Result: Higher early-summer SST = less Themisto in auklet diets. Themisto libellula p = 0.023 Percent T. libellula in CRAU diets R2 = 0.863 May Mean Sea Surface Temperature

  28. Themisto amphipods Hypothesis:Themisto will be less available as sea surface temperatures increase. Amphipods Result: Higher early-summer SST = less Themisto in auklet diets. Themisto libellula Will T. libellula decline throughout a warming Bering Sea? p = 0.023 Percent T. libellula in CRAU diets R2 = 0.863 May Mean Sea Surface Temperature

  29. 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

  30. 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?

  31. Implications for other wildlife • 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. Photo source: Universititet I Oslo Neocalanus Themisto Source: ChartingNature.com

  32. Acknowledgements The Savoonga Native Corporation • Coauthors: • Dan Roby, Lisa Sheffield, Adrian Gall, David Irons and Kathy Turco • Funding: • USFWS, USGS-Oregon Cooperative Fish and Wildlife Research Unit, Spencer Sealy (UM) Calvin Akeya, Tim and Roland Alowa, Blake Roberts, Mike Denega, Rebecca Woodgate, Karen Fischer, and everyone in Savoonga, AK!

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