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