Biological Implications of Arctic Change
Jacqueline M. Grebmeier Department of Ecology and Evolutionary Biology
University of TennesseeKnoxville, Tennessee, 37932, USA
SEARCH Open Science MeetingSeattle, 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
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
Satellite view of phytoplankton content
[G.Cota]
July 24, 2002
Ice algae and large open-water diatoms
Smaller diatoms/detritus
[E.Sherr]
[E.Sherr]
Alaska
Russia
Chukchi Sea
Beaufort SeaEast Siberian Sea
Bering Sea
Integrated chlorophyll (mg/l), compiled over the period 1975-1996
[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
Alaska
Russia
Bering Sea
Chukchi Sea
Beaufort SeaEast Siberian Sea
Biomass g m-2
[Dunton, Maidment and Grebmeier, 2003, in prep.]
[M. Webber-USFWS]
Walrus herd in the Chukchi Sea– June 2002
Schematic of food web in the northern Bering and Chukchi Seas (Grebmeier and Dunton, 2000)
Clam food in walrus stomachs
[G.Sheffield]
[G.Sheffield]
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
20 Apr 01 04 May 01 14 May 01
19 Apr 99 03 May 99 14 May 99
Sea Ice Melt 100% 50% 95% 40% 90% 30% 80% 20% 70% 10% 60% 0%
Ice Concentration
[J.Clement, 2002-MS thesis)
Spectacled Eider and benthic food supply (dominated by bivalves: Nuculana radiata, Nucula belloti, Macoma calcarea)
[photos by J. Lovvorn]
• 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
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]
[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
http://sbi.utk.edu
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
SBI Spring and Summer cruises 2002
East Hanna Shoal (summer 2002)[Codispoti et al.-SBI Hydro Team]
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
SBI Cruise: May-June 2002 SBI/LTO Cruises: July-August 2002
[Grebmeier and Cooper, unpubl.data]
EHS
BC
BC
EHS
Ammonium and silicate sections from East Hanna Shoal (EHS) and Barrow Canyon (BC) in summer 2002
[Codispoti et al.-SBI Hydro Team]
IBCAO Map
SBI
CASES
• SBE sites
• past polynya studies
• ASOF mooring sites
• EO sites
• ice camps
• educational sites
• smaller projects
JWACS
CABANERA
Laptev Sea Project
SIRRO
SWITCHYARD
ESSIARC/AARI
Xuelong Cruise
ASOF
BS-EO
NP-EO
NOW
NEWASOF
PACE
NABOS
SOME ARCTIC PROJECTS AND ONGOING/PLANNED SHELF-BASIN EXCHANGE (SBE) STUDY SITES
IBCAO Map
Possible SEARCH Pan-Arctic Shelf-Basin Exchange transect lines for standard physical and biogeochemical, process-oriented measurements
ASOF
ASOF
• SBE sites
• ASOF mooring sites
• EO sites
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