Science of the Total Environment 351–352 (2005) 247–263 www.elsevier.com/locate/scitotenv Mercury and other trace elements in a pelagic Arctic marine food web (Northwater Polynya, Baffin Bay) Linda M. Campbell a, Ross J. Norstrom b, Keith A. Hobson c, Derek C.G. Muir a, Sean Backus a, Aaron T. Fisk d,* aNational Water Research Institute, Environment Canada, 867 Lakeshore Road, Burlington, Ontario, Canada, L7R-4A6 bChemistry Department, Carleton University, Ottawa, Ontario, Canada K1A 0H3 cPrairie and Northern Wildlife Research Centre, Canada; Canadian Wildlife Service, Saskatoon, SK, Canada, S7N 0X4 dWarnell School of Forest Resources, University of Georgia, Athens, Georgia, 30602-2152 USA Received 15 December 2004; received in revised form 3 February 2005; accepted 14 February 2005 Available online 1 August 2005 Abstract Total mercury (THg), methylmercury (MeHg) and 22 other trace elements were measured in ice algae, three species of zooplankton, mixed zooplankton samples, Arctic cod (Boreogadus saida), ringed seals (Phoca hispida) and eight species of seabirds to examine the trophodynamics of these metals in an Arctic marine food web. All samples were collected in 1998 in the Northwater Polynya (NOW) located between Ellesmere Island and Greenland in Baffin Bay. THg and MeHg were found to biomagnify through the NOW food web, based on significant positive relationships between log THg and log MeHg concentrations vs. d15N in muscle and liver. The slope of these relationships for muscle THg and MeHg concentrations (slope=0.197 and 0.223, respectively) were similar to those reported for other aquatic food webs. The food web behavior of THg and d15N appears constant, regardless of trophic state (eutrophic vs. oligotrophic), latitude (Arctic vs. tropical) or salinity (marine vs. freshwater) of the ecosystem. Rb in both liver and muscle tissue and Zn in muscle tissue were also found to biomagnify through this food web, although at a rate that is approximately 25% of that of THg. A number of elements (Cd, Pb and Ni in muscle tissue and Cd and Li in seabird liver tissue) were found to decrease trophically through the food web, as indicated by significantly negative relationships with tissue-specific d15N. A diverse group of metals (Ag, Ba, La, Li, Sb, Sr, U and V) were found to have higher concentrations in zooplankton than seabirds or marine mammals due to bioconcentration from seawater. The remaining metals (As, Co, Cu, Ga, Mn, Mo and Se in muscle tissue) showed no relationship with trophic position, as indicated by d15N values, although As in liver tissue showed significant biomagnification in the seabird portion of the food web. D 2005 Published by Elsevier B.V. Keywords: Arctic; Metals; Mercury; Methyl mercury; Stable nitrogen isotopes; Seabirds; Biodilution; Biomagnification * Corresponding author. Tel.: +1 706 542 1477. E-mail address: [email protected] (A.T. Fisk). 0048-9697/$ - see front matter D 2005 Published by Elsevier B.V. doi:10.1016/j.scitotenv.2005.02.043 248 L.M. Campbell et al. / Science of the Total Environment 351–352 (2005) 247–263 1. Introduction Arctic environments has been declining, partially due to increased global limits on alkyl lead additives in The occurrence of heavy metals in Arctic marine gasoline (Jensen et al., 1997). Cd in seal livers and food webs is of concern despite limited anthropo- other dietary items is of concern since it has been genic activity in this region. Mercury (Hg) and other found that traditional hunters and their families can metals have been detected in various biota and en- potentially ingest Cd above Health Canada guide- vironmental samples across this region, and there has lines of 450 mg Cd/week (Jensen et al., 1997; been concern about sources and concentrations in Johansen et al., 2004). Despite their importance in sample food items frequently consumed by humans the Arctic, the fate and dynamics of metals and other and wildlife (Dietz et al., 1996; Fisk et al., 2003). In elements in Arctic marine systems remain largely fact, concentrations of many metals in Arctic biota unknown. are similar to concentrations measured in temperate Polynyas are persistent regions of open water sur- regions (Muir et al., 1999). While Hg and other rounded by sea ice and are a vital component of Arctic metals are found naturally in the environment, the marine ecology (Stirling, 1980). Polynyas are also origin of elevated concentrations observed in biota significant from a socio-economic perspective, since from across the Arctic have been attributed to an- the Inuit from Canada and Greenland hunt tradition- thropogenic sources in southern regions (Muir et al., ally important animals such as ringed seals Phoca 1999). Of particular concern are lead (Pb), cadmium hispida that congregate in polynyas. The Northwater (Cd) and Hg compounds, which have reached con- Polynya (NOW) is the largest (50,000 km2) and most centrations in many Arctic biota that exceed Health productive polynya in the Canadian Arctic (Fig. 1). Canada and World Health Organization guidelines As such, it supports large populations of seabirds and for human consumption (Muir et al., 1999). Pb in mammals in northern Baffin Bay. ELLESMERE ISLAND N GREENLAND Nor thwater Polynya B AF FIN IS LA ND (LANCASTER SOUND) CANADA HUDSON’S BAY Fig. 1. Approximate geographical position of the Northwater Polynya between Greenland and Ellesmere Island in Baffin Bay in May/June. Baffin Island and Lancaster Sound are also indicated. L.M. Campbell et al. / Science of the Total Environment 351–352 (2005) 247–263 249 The dynamics of carbon and anthropogenic persis- Table 1 tent contaminants in the NOW polynya food web have List of biota from the NOW marine food web analysed for metals, along with assigned codes used in subsequent tables previously been characterized using stable nitrogen (d15N) and carbon (d13C) isotopes (Fisk et al., 2001; Organism Code Common name Taxonomic name TL Hobson et al., 2002). Stable isotopes have increasing- Primary IALG Ice algae ~ 1.3 ly been used in aquatic ecosystems to evaluate food Invertebrate CHYP Copepod Calanus 2.0 hyperboreus web structure and energy pathways. Stable nitrogen Invertebrate ZOOP Mixed ~ 2.2 15 isotope ratios (d N) increases 2x to 4x with each zooplanktona trophic level, providing a means to assess trophic Invertebrate TLIB Amphipod Themisto libellula 2.5 level (Peterson and Fry, 1987). In contrast, d13C Invertebrate MOCC Mysid Mysis oculata 2.7 values often demonstrate lower trophic fractionation Fish ACOD Arctic cod Boreogadus saida 3.7 x x Sea bird DOVE Dovekie Alle alle 3.2 (0.8 to 1 ), and are useful for evaluating sources of Sea bird BLKI Black-legged Rissa tridactyla 3.8 primary production within a food web (Peterson and kittiwake Fry, 1987). Stable isotopes can also be used to esti- Sea bird BLGU Black guillemot Ceppus grylle 3.9 mate the rate of biomagnification of a chemical across Sea bird TBMU Thick-billed Uria lomvia 3.9 the entire food web. The slope of contaminant levels murre 15 Sea bird IVGU Ivory gull Pagophilia eburnea 4.0 against trophic levels as determined by d N, often Sea bird NOFU Northern fulmar Fulmarus glacialis 4.1 called trophic magnification factors (TMFs) of con- Sea bird GLGU Glaucous gull Larus hyperboreus 4.7 taminants, have been applied in Arctic food webs to Sea bird THGU Thayer’s gull Larus thayeri 4.9 determine the rate of biomagnification through the Mammal RSEA Ringed Seal Phoca hispida 4.6 food web (Atwell et al., 1998; Borga˚ et al., 2004). The common and taxonomic names are indicated. Mean estimated trophic levels (TL) were estimated from d15N values of muscle The objective of this research was to assess the 15 trophic transfer of 22 elements and methylmercury in samples using Eqs. (2) and (3) (see text). The mean muscle d N values are listed in Table 2, along with those for liver samples. the NOW marine food web by determining metal and a Mixed zooplankton were predominantly Calanus copepods. stable isotopes of nitrogen and carbon values in a wide range of species. (Table 1) were obtained from Inuit hunters from Ausuittuq (Grise Fijord) in Ellesmere Island and 2. Methods Qaˆnaˆq in north western Greenland. All samples were placed in Whirl-Pak bags, cryo-vials or alu- 2.1. Sample collection minium foil and frozen until analysed for stable isotopes or elements. Samples were collected during May 1998 from the CCGC Pierre Radisson in the Northwater Po- 2.2. Element analysis lynya located in northern Baffin Bay (Fig. 1). Zooplankton were collected from vertical tows Element samples were analysed at the National from bottom to surface using a 1-m diameter zoo- Laboratory for Environmental Testing (NLET) at plankton net with 520-Am mesh. After collection, National Water Research Institute in Burlington, zooplankton were either unsorted (bmixedQ)or Ontario (National Laboratory for Environmental sorted by species, including the amphipod Themisto Testing, 2003). Total mercury in liver and muscle libellula, the calanid copepod Calanus hyperboreus tissue (NLET Method 02-2802) was analysed by and the mysid, Mysis oculata (Table 1). Arctic cod cold vapour atomic absorption spectrometry Boreogadus saida (Table 1) were opportunistically (CVAAS), while methylmercury in muscle tissue sampled at one location using hand-held nets. Sea- was determined by GC–atomic emission detection birds (Table 1) were collected by shotgun from a (AED). Liver tissue was not analysed for MeHg. Zodiac boat, measured and sexed, and dissected for Analyses of 22 elements in liver and muscle samples liver and muscle samples. Ringed seal P. hispida (NLET Method 02-2705), were analysed by induc- (age 8 to 10 years only) liver and muscle samples tively coupled plasma-Sector Field spectrometry 250 L.M. Campbell et al. / Science of the Total Environment 351–352 (2005) 247–263 (ICP-SFMS), with 20 elements analysed at low res- based on the PeeDee Belemnite for 13C and atmo- 15 olution (Ag, Ba, Cd, Co, Cr, Cu, Ga, La, Li, Mn, spheric N2 for N.