Biological Implications of Arctic Change
Jacqueline M. Grebmeier
Department of Ecology and Evolutionary Biology
University of Tennessee
Knoxville, Tennessee, 37932, USA
SEARCH Open Science Meeting
Seattle, Washington, USA
October 27, 2003
Introduction
• high latitude ecosystems sensitive to climate
change
• recent reduction sea ice, increased seawater
temperature
• changes in the timing, extent, composition
and location of annual production (both
primary and secondary trophic levels)
important in pelagic-benthic coupling
• polar systems can have short food chains, such that changes in lower
trophic levels can cascade more efficiently to higher trophic organisms (e.g.,
seals, whales, walruses, seabirds and ultimately man)
• potential impacts of change have broad-reaching implications for long-term
ecosystem structure
Bering Strait Region
• Bering Sea possibly shifting towards an
earlier spring transition between ice-covered
and ice-free conditions
• Surface sea temperature increase in the
1990s vs the 1980s, tied to the Arctic
Oscillation further to the north (Stabeno and
Overland, 2001, EOS 82:317-321)
• Retrospective benthic studies in the region
indicate changes occurring in both carbon
deposition and benthic biomass since the late
1980’s
• Examples of likely cascade effect on benthic-feeding high trophic organisms
(diving seaducks, migrating whales)
June 3, 2002
Ice algae and large open-water
diatoms
[E.Sherr]
Satellite view of
phytoplankton content
 high phytoplankton biomass in
nutrient-rich Bering Sea/Anadyr
water in northern Bering&Chukchi
Seas, and in Barrow Canyon region
in spring; overall less production in
summer
Smaller diatoms/detritus
July 24, 2002
[E.Sherr]
[G.Cota]
Integrated chlorophyll (mg/l), compiled over
the period 1975-1996
East Siberian Sea
Beaufort Sea
Alaska
Chukchi Sea
Russia
Bering Sea
[Dunton, Maidment and Grebmeier, 2003, in prep.]
Sediment oxygen uptake (mmol O2m-2 d-1); 1984-1995
[Grebmeier and Dunton, 2000]
Circulation Superimposed on the Distribution
of Benthic Biomass: 1970-1990
East Siberian Sea
Beaufort Sea
Chukchi Sea
Russia
Alaska
Bering Sea
Biomass g m-2
[Dunton, Maidment and Grebmeier, 2003, in prep.]
Walrus herd in the
Chukchi Sea– June 2002
[G.Sheffield]
[M. Webber-USFWS]
Clam
food in
walrus
stomachs
[G.Sheffield]
Schematic of food web in the
northern Bering and Chukchi Seas
(Grebmeier and Dunton, 2000)
Bering Strait Environmental
Observatory
(Cooper, Grebmeier, Codispoti
and Sheffield)
(http://arctic.bio.utk.edu)
Objectives
1) land-based marine sampling
program on Little Diomede Island in
Bering Strait
2) annual July oceanographic study
in collaboration with Eddy Carmack
(IOS/DFO Canada); deploy mooring
in A-SLIP region 2003
3) Marine mammal collection
program
Ice Concentration
100%
95%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
Sea Ice Melt
19 Apr 99
03 May 99
14 May 99
20 Apr 01
04 May 01
14 May 01
[J.Clement, 2002-MS thesis)
[photos by J. Lovvorn]
Spectacled Eider and
benthic food supply
(dominated by
bivalves: Nuculana
radiata, Nucula belloti,
Macoma calcarea)
Bering Strait Environmental
Observatory maintains sites south of
St. Lawrence Island
[Simpkins, M.A, L.M. Hiruki-Raring, G. Sheffield, J.M.
Grebmeier, and J.L. Bengtson (Polar Biology 2003]
• overall decline late 1980’s to 1998, then
level out in both sediment oxygen uptake
(indicator of carbon flux to sediments) and
overall benthic standing stock
• retrospective study indicates changes in
dominant bivalve from Macoma calcarea to
Nuculana radiata
[Grebmeier, J.M, , and L.W. Cooper, in prep, 2003]
Chirikov Basin
in the 1980’s
• Basin is downstream end of Gulf of
Anadyr-Bering Sea ‘Greenbelt’
• Pelagic-benthic coupling supports high
benthic biomass (Grebmeier et al.
1989, Mar. Ecol. Prog. Ser.)
• Dense assemblages of tube-building
ampeliscid amphipods
• Basin is “one of the most productive
benthic communities in the world”
(Highsmith and Coyle,1990, Nature)
• Gray whale surveys indicate feeding
area in northern Bering Sea (Moore et
al., 2003, C.J.Zool.)
Drop in Benthic Productivity
• Highsmith and Coyle report
evidence of 30% production
downturn 1986-88 (MEPS,
1992)
• Grebmeier et al. document
continued decline of
ampeliscids @ 4 stations
(Moore et al. 2003, Can. J.
Zool.)
• LeBoeuf et al. (2002) link this
decline in the Chirikov Basin as
causal to gray whale mortalities
Western Arctic Shelf-Basin
Interactions (SBI) project
Current studies as part of the SBI
global change project are
investigating the production,
transformation and fate of carbon at
the shelf-slope interface in the
northern Chukchi and Beaufort
Seas, downstream of the
productive shallow western Arctic
shelves, as a prelude to
understanding the impacts of a
potential warming of the Arctic
http://sbi.utk.edu
SBI Spring and Summer cruises 2002
East Hanna Shoal (summer 2002)
[Codispoti et al.-SBI Hydro Team]
SBI Cruise: May-June 2002
SBI/LTO Cruises: July-August 2002
Sediment oxygen uptake (mM O2 m-2 d-1), resulting in high ammonium, silica,
and DOC flux out of the shelf sediments both spring and summer
[Grebmeier and Cooper, unpubl.data]
EHS
BC
EHS
BC
Ammonium and silicate sections from East Hanna Shoal (EHS) and
Barrow Canyon (BC) in summer 2002
[Codispoti et al.-SBI Hydro Team]
Xuelong Cruise
BS-EO
SBI
JWACS
ESS
IARC/AARI
CASES
Laptev Sea
Project
NABOS
NP-EO
SOME ARCTIC
PROJECTS AND
ONGOING/PLANNED
SHELF-BASIN
EXCHANGE (SBE)
STUDY SITES
SIRRO
NOW
SWITCH
YARD
• SBE sites
CABANERA
PACE
ASOF
NEW
• past polynya studies
• ASOF mooring sites
• EO sites
ASOF
• ice camps
• educational sites
• smaller projects
IBCAO Map
Possible SEARCH
Pan-Arctic ShelfBasin Exchange
transect lines for
standard physical and
biogeochemical,
process-oriented
measurements
• SBE sites
• ASOF mooring sites
ASOF
• EO sites
ASOF
IBCAO Map
Summary
• Bering Strait region may be shifting towards an earlier spring transition
between ice-covered and ice-free conditions
• Changes in the timing of productivity over the shelf and slope regions may
rapidly impact trophic structure, and ultimately carbon transport from the shelf
to the Arctic basin
• Retrospective benthic studies in the region indicate changes have occurred
in both carbon deposition and benthic biomass since the late 1980s
• Long-term studies in focused regions are critical for differentiating climate
change impacts from natural variability in the system
• The international SBE working group recommends time series physical
and biogeochemcial data be collected at pan-Arctic shelf-basin transect lines
to detect change in this critical ecosystem