the bering sea is it just a warmer barents sea? george l. hunt, jr. university of california, irvine...
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The Bering SeaIs it just a Warmer Barents Sea?
George L. Hunt, Jr.University of California, Irvine
and
Bernard MegreyNOAA Alaska Fisheries Science Center
Contents
• Physical Comparison
• Climate and Advective Processes
• Productivity
• Biomass
• Ecosystem Structure
Bering & Barents Seas: Physical
ParameterSE Bering
SeaBarents Sea
Latitude 54-60 °N 68-85 °N
Area > 200m (km2) 21.1 x 103 533.2 x 103
Area < 200m (km2)
Advection
463.4 x 103
~1 Sv
472.9 x 103
~4 Sv
Nitrate (mM m-3) 10-30 10 -12
Phosphate (mM m-3) 1.0-2.0 0.85
Silicate (mM m-3) 25-60 6-8
Data from: Dommasnes et al., 2001; Sakshaug and Walsh, 2000; Aydin et al., 2002; ACIA, In Press
Lower Trophic Level Productivity
Bering Sea Barents Sea
Inner Middle Outer Arctic Atlantic
Tot. Primary Production
(g C m -2 y-1)50-70 150-175 160 <90 <200
New Prod. <20 30-50 ? <40 70-110
Secondary Production
2-6 8-30 16-50 1-18 3-17
Dom. Taxa Diatoms Phaeocystis
Sakshaug & Walsh 2000
Abundance Low Medium High
Cold years 35% 7% 1%
Warm years 31% 14% 12%
Year-class Abundance of Cod
H. Loeng & G. Ottersen
Bering and Barents Seas- Biomass (tonnes km-2)
Taxon Barents 1990 high capelin
Barents 1995 low capelin
E. Bering Sea 1980s
Phytoplankton
Crust. Zoops.20
58
20
58
11.8
26
Capelin
Herring 4.17
1.34
0.14
3.33
-
0.78
Benthic Crust. 1.43 1.38 > 2.2
Flatfish 1.1 1.1 11.3
Gadids 1.2 2.6 35.9
Pinnipeds 0.87 0.87 0.22
Whales 0.20 0.20 0.26Blanchard et al., 2002; Aydin et al., 2002
Productivity: Bering & Barents SeasBering Sea Barents Sea
Taxon P/B (y-1) P P/B (y-1) P
Phytoplankton 170 2000 117.73 1765
Copepods 6 330 10 500
Large Zoops 5.5 242 4 67.5
Forage Fish Herring
0.8
1
-
0.78
1
0.38
1.13
1.24
Ad Pollock/ Atlantic Cod
0.5
13.73 1.2 0.54
Small Flatfish 0.4 3.67 1 0.7
Benthic Infauna
1.37 63.84 1.5 99
Aydin et al., 2002; Blanchard et al., 2002
Summary
Why does the Bering have a pollock
biomass 30X that of cod in the Barents?
• Nutrients & Primary Prod similar • Bering -Diatoms, Barents- Phaeocystis
(Sakshaug & Walsh)
• Bering & Barents Sensitive to Timing of Bloom
• Zooplankton more abundant and productive in Bering
• Pollock eat zooplankton- lower trophic level (3.3 vs 4.3)
• Forage fish essential for cod; More (capelin) in Barents;
• Pollock cannibalistic- do not need forage fish
• Pollock 25X more productive • More seals in Barents Sea
Summary
Why does the Bering have a pollock
biomass 30X that of cod in the Barents?