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: ) 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]

Alaska Russia Chukchi Sea Beaufort Sea East Siberian Sea Bering Sea Integrated chlorophyll (mg/l), compiled over the period [Dunton, Maidment and Grebmeier, 2003, in prep.]

Sediment oxygen uptake (mmol O 2 m -2 d -1 ); [Grebmeier and Dunton, 2000]

Circulation Superimposed on the Distribution of Benthic Biomass: Alaska Russia Bering Sea Chukchi Sea Beaufort Sea East 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]

Bering Strait Environmental Observatory (Cooper, Grebmeier, Codispoti and Sheffield) ( 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 ) Marine mammal collection program

20 Apr 0104 May 0114 May Apr 9903 May 9914 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 (MEPS, 1992) Grebmeier et al. document continued decline of 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

SBI Spring and Summer cruises 2002

East Hanna Shoal (summer 2002) [Codispoti et al.-SBI Hydro Team]

Sediment oxygen uptake (mM O 2 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 2002SBI/LTO Cruises: July-August 2002 [Grebmeier and Cooper, unpubl.data]

EHS 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 SWITCH YARD ESS IARC/AARI Xuelong Cruise ASOF BS-EO NP-EO NOW NEW ASOF 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 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