Blake.indd 123Blake 2006: Polar Research 25(2), 123–137 Occurrence of the Mytilus edulis complex on Nordaustlandet, Svalbard: radiocarbon ages and climatic implications Weston Blake, Jr. Fragments of the blue mussel (Mytilus edulis complex) are present on raised beaches in the vicinity of Langgrunnodden and Kinnvika, north- western Nordaustlandet, Svalbard. Both of these localities are north of 80° N. New radiocarbon age determinations, together with earlier results, show that Mytilus colonies were present in this area for much of the fi rst half of Holocene time—from approximately 9000 to 5800 14C yr BP. Mytilus has also been recorded farther south in Nordaustlandet, at three localities in Wahlenbergfjorden. Age determinations of shells at two of these sites have yielded results in the range of 7400 to 6900 14C yr BP. The arrival of Mytilus to Nordaustlandet coincided with the early Holocene infl ux of warm North Atlantic Water off the west coast of Spitsbergen. The drastic warming in early Holocene time, which resulted in the rapid melt-off of glaciers and ice caps in Svalbard, also facilitated the establish- ment and perserverance of Mytilus colonies at this high latitude. W. Blake, Jr., Geological Survey of Canada, 615 Booth St., Ottawa, Ontario K1A 0E9, Canada, weblake@NRCan.gc.ca. The common blue mussel (Mytilus edulis) has featured in Arctic scientifi c literature for well over a century. Among the discoveries of the 1861 Swedish expedition to Spitsbergen, for example, were fragments of M. edulis at the westernmost point of Nordaustlandet (Figs. 1, 2), a locality then known as Shoal Point, now called Lang grunn- odden (Chydenius 1865). Until recently the Arctic occurrences of this wide-ranging species have been referred to M. edulis L., but Feder et al. (2003) have shown that specimens collected alive at Barrow, on the northern coast of Alaska, are M. trossulus on the basis of DNA analysis (see also Norton & Feder 2006). For the purposes of the present paper, and following Feder et al. (2003), the M. edulis complex will be taken to include both species, should M. trossulus turn out to be present in Svalbard also. Equally important as the species assignment, in terms of the discussion here, is the fact that Mytilus has long been regarded as an indicator of somewhat warmer sea conditions than those which have obtained throughout the past two cen- turies in Svalbard (Nathorst 1901a; Hoel 1909; Högbom 1911, 1913; Elton & Baden-Powell 1931; Feyling-Hanssen & Jørstad 1950; Feyling-Hans- sen 1955 [includes a detailed discussion and many references]; Feyling-Hanssen & Olsson 1960; Funder 1992; Hjort et al. 1992; Salvigsen et al. 1992; Hjort et al. 1995; Salvigsen 2002, 2005; Salvigsen & Høgvard 2005), in Greenland (Nath- orst 1901b; Noe-Nygaard 1932; Hjort & Funder 1974; Funder 1978, 1990; Kelly 1985; Funder & Fredskild 1989; Funder & Weidick 1991) and elsewhere in the High Arctic, such as on Coburg Island in the northern tier of the islands of the 124 Mytilis edulis on Nordaustlandet, Svalbard Canadian Arctic Archipelago (Blake 1973). Although M. edulis has occasionally been found alive on materials that have drifted to Sval- bard waters with the West Spitsbergen Current (Heintz 1926; Christiansen 1965; Salvigsen 2002, 2005), until recently it has not been found living there. Now Mytilus has been reported from both Bjørnøya (Węsławski et al. 1997; although Berge et al. [2006] emphasize that the few individuals found there do not constitute a population) and from a group of skerries in outer Isf jord en, Spits- bergen (Berge et al. 2005). In the latter locali- ty its appearance is attributed to the “unusually high northward mass transport of warm Atlan- tic water resulting in elevated sea-surface tem- peratures in the North Atlantic and along the west coast of Svalbard” (Berge et al. 2005: 167). The colony at this site has been shown to be M. edulis on the basis of DNA analysis (Berge et al. 2006). It is interesting to note that Mytilus was not recorded in 1908 in the same general area by Odhner (1915), despite an extensive programme of dredging, and Berge et al. (2006) also observe that numerous surveys along the western coast of Spitsbergen over the last 30 years have failed to reveal the presence of Mytilus. However, Feder et al., as a result of extensive work along the north- ern and north-western coasts of Alaska, reached a very different conclusion with regard to the value of Mytilus as an indicator of warmer sea condi- tions: “...water temperature cannot be the prima- ry determinant of Mytilus persistence in the 20° 80° 80° 24°18° Sjuoyane Phippsoya Søre Repøya Nordaustlandet Spitsbergen Kong Karls Land Edgeøya Storøya 100 100 1 0 0 1 0 0 100 10 0 10 0 100 10 0 20 0 200 1 0 0 1 0 0 200 20 0 40 0 60 0 100 200 2 0 0 200 200 Lågøya Wargentinflya Søre Russoya Nordre Russøya Sveanor Brageneset Idunneset Gyldénøyane V aigattoyane Rijpdalen R ijp fjo rd e n D u ve fjo rd e n S ab in eb uk ta Li nd ha ge nb uk ta Zorgdragerfjorde n Arkvatnet G le nh al vø ya F in n M al m gr en fjo rde n Is fjo rd en Dalvågen Brennevinsfjorde n L a d y F ra n klin fjorden Murchisonfjorden Kinnvika D etterbukta L a n g g ru n n odden H in lo p e n re n n a Wa hlen berg fjorde n L o m fjo rd e n H I N L O P E N S T R E T E T Bodleybreen Brånevatnet Etonbreen N O R D A U S T L A N D E T A U S T F O N N A V E S T F O N N A Krystallvatnet Søre Franklinbreen P R IN S O S C A R S L A N D Is isp yn te n Svartkn ausflya Bråsvellbreen glacier ice moraine sites with 14C data sites with dated Mytilus contour interval, 200 m depth contour, 100 m 25 km Fig. 1. Location map of Nordaustlandet, Svalbard, showing sites mentioned in the text. Illustration based on a 1:1 000 000 map of Svalbard by Kristiansen & Sollid (1986). Bjørnøya, at 74° 30 'N & 19° E, is ca. 225 km SSE of the southern tip of Spitsbergen. 125Blake 2006: Polar Research 25(2), 123–137 Arctic. Low water temperature is known to prolong dispersive life-cycle stages and to slow later development and growth, but it has not been shown to limit Mytilus sur- vival or reproduction. We suggest that the presence of this bivalve during periods of higher sea level during the early Holocene is a response to lower and more variable salinity of coastal waters rather than to increased temperature” (2003: 402). Thirteen radiocarbon age determinations of M. edulis in raised beaches are now available from Nordaustlandet, the northernmost of the main islands in the Svalbard archipelago. All except two of these determinations are based on collections made by the writer north of the 80th parallel, and nine of the 13 age determinations are based on single valves or single shell frag- ments, thus eliminating the chance of mixing shell material of different ages. These occur- rences are the most northerly known in which M. edulis is found in abundance on raised beach- es. It thus seems appropriate to discuss the sig- nifi cance of these fi nds in light of the hypothe- sis advanced by Feder et al. (2003) and the 2004 discovery of a colony of living M. edulis near the entrance to Isfjorden, Spitsbergen (Berge et al. 2005; Berge et al. 2006), some 230 km to the south-west of Langgrun nodden. Materials and methods Collections and radiocarbon ages of Mytilus shells from Nordaustlandet Following the 1861 discovery of M. edulis at Langgrunnodden, when numerous shells were collected by A. J. Malmgren at about 9 to 15 m a.s.l. in clay (Hägg 1950), the second fi nd of this species in Nordaustlandet was made by K. S. Sandford, geologist on the 1924 Oxford Uni- versity Expedition. He reported rare valves of the blue mussel in boulder clay at ca. 55 m a.s.l. at a site along the northern shore of inner Wahlenberg- fjorden (Fig. 1 and Sandford 1929). Until recent- ly the shells in this collection had not been dated, but the elevation reported is some 40 m higher than any of the previously dated Holocene collec- tions of Mytilus from Nordaustlandet (Table 1). Thus, it seemed reasonable to surmise that Sand- ford’s collection might represent pre-last glacia- tion material, possibly transported upward by a southward advancing Bodleybreen, or possibly moved by an enlarged Etonbreen fl owing west- ward out the fjord. Both glaciers have a history of surging (Dowdeswell 1986a, 1986b; Lefau- connier & Hagen 1991). Pelecypod shells of sev- eral other species which predate the last glacia- tion have been collected at numerous sites around Nordaustlandet and on Sjuøyane to the north (Blake 1961a, 1962, 1981, 1989, 1995; Olsson & Fig. 2. Oblique aerial view north-west across Murchisonfjorden, showing the principal areas where Mytilus has been collected: Kinnvika and Langgrunnodden. This image is a portion of photograph S38-1247 taken by B. Luncke, 28 July 1938; between 0540 and 0615 hours. (Photograph courtesy of the Norwegian Polar Institute.) 126 Mytilis edulis on Nordaustlandet, Svalbard Blake 1962; Salvigsen & Nydal 1981; Forman & Ingólfsson 2000). Also, pre-Holocene Mytilus shells have been reported from one of the inner branches of Isfjorden, Spitsbergen (Mangerud & Svendsen 1992a, 1992b). However, the single robust valve dated from Sandford’s collection turned out to be Holocene, the lab-reported age being 7370 ± 20 14C yr BP (lab. no. UCIAMS-21868), or 6930 ± 20 14C yr BP after the reservoir effect is taken into account (Table 1, Fig. 3). Because of its elevation, well above early Holocene shells collected by the writer at ca. 43 m a.s.l. (Table 2), it seems likely that both shells and the enclosing ‘boulder clay’ do indeed represent glacier-transported material, from a late Holocene readvance of Bodleybreen. Table 1. Radiocarbon ages on shells of the Mytilus edulis complex, Nordaustlandet, Svalbard. Field no. a Elev. (m) Weight used (g) Lab. no. b Age, reported by lab. Age, corrected for apparent age of seawater c δ13C (PDB) ‰ Comments Langgrunnodden/Detterbukta WB-58-303 ∼14.0 0.16 UCIAMS-19833 9470 ± 25 9030 ± 25 0.1 ± 0.1 Single fragment. WB-58-303 ∼14.0 0.27 UCIAMS-21867 9490 ± 20 9050 ± 20 –0.65 ± 0.1 Single fragment. WB-58-312 WB-58-312 9.0 9.0 } 90.0 U-173{ U-174 9200 ± 190 8530 ± 190 8760 ± 190 8090 ± 190 –2.0 –1.0 Numerous fragments—innermost 13 % of shell material. Next 14 % of shell material. Outermost 73 % removed by HCl leach. WB-58-312 9.0 0.23 UCIAMS-20526 8790 ± 15 8350 ± 15 –0.4 ± 0.1 Single fragment. Kinnvika, Murchisonfjorden WB-90-28 14.5 0.23 Ua-2102 9060 ± 90 8620 ± 90 — Single fragment of blue-violet shell only. WB-90-28 14.5 0.16 UCIAMS-20527 8960 ± 20 8520 ± 20 0.6 ± 0.1 Single fragment of blue shell. WB-66-178 7.5 — GaK-1916 d 7530 ± 130 7530 ± 130 — Numerous fragments. WB-66-178 7.5 0.76 UCIAMS-16174 7095 ± 20 6655 ± 20 –0.27 ± 0.1 Single fragment. WB-90-25 5.1 0.14 Ua-11158 6435 ± 105 5995 ± 105 0.5 Single fragment. Inner fraction dated. WB-90-25 5.1 0.11 UCIAMS-19834 6335 ± 25 5895 ± 25 0.2 ± 0.1 Single fragment. Wahlenbergfjorden Sa-97-100 ∼10 5.0 T-13426 7260 ± 105 7260 ± 105 e — 1 whole valve plus several large fragments, all of good quality. Coll. A. M. Tebenkov. OUM QX. 1639 ∼55 0.40 UCIAMS-21868 7370 ± 20 6930 ± 20 –0.74 ± 0.1 Single left valve, 6 cm long, 2.5 cm high, shell 2 - 3 mm thick; periostracum partly intact. Coll. K. S. Sandford. a All samples with fi eld designation WB were collected by W. Blake, Jr.; R. Bergström helped make the 1958 collections. b Laboratory designations: U = Uppsala; Ua = Tandem Accelerator Laboratory, Uppsala; UCIAMS = University of California, Irvine (AMS); GaK = Gakushuin University, Japan; T = Trondheim. c Following Mangerud & Gulliksen (1975) a reservoir effect of –440 years is applied to samples with designations UCIAMS, U and Ua. d Doubts about the accuracy of some Gakushuin 14C ages have been expressed earlier (Blake 1980, 1989); the Gakushuin determination on marine shells is corrected to δ13C = 0.0 ‰, so no additional correction is applied (Kigoshi et al. 1962). e As reported by Salvigsen (2002) with a built-in correction of –440 years. 127Blake 2006: Polar Research 25(2), 123–137 Following Sandford’s fi nd in Wahlenberg- fjorden the next discovery of M. edulis in Nord- austlandet was made in 1931, from two sites on the southern side of Murchisonfjorden (Figs. 1, 2): at 14.5 m a.s.l. near Sveanor, the base of the Swedish–Norwegian Arctic Expedition, and on nearby Søre Russøya, where occasional shells were found in the raised beaches at an approx- imate elevation of 16 to 19 m (Kulling 1936). Although several later visits have been made to these general locations, unfortunately no addi- tional fi nds of Mytilus have been recorded. Next, J. J. Donner and R. G. West, members of the 1955 Oxford University Expedition, collected two valves of M. edulis at 4.5 m a.s.l. near the top of a disturbed section at Idunneset, on the north side of Wahlenbergfjorden, near the mouth of the fjord (Donner & West 1957). These shells have not been dated. Mytilus edulis shells were not found on the nearby Gyldénøyane at the mouth of Wahlenbergfjorden (Elton & Baden-Powell 1931), nor were any discovered in the vicini- ty of the 1955 expedition’s base, Brage neset, at the northern entrance to the fjord (Donner & West 1957, 1995). More recently, in 1997, A. M. Tebenkov collected M. edulis shells at Brånevat- net in innermost Wahlenbergfjorden (actually east of the present-day head of the fjord) at ca. 10 m a.s.l., and these shells yielded an age of 7260 ± 105 14C yr BP (T-13426; Salvigsen 2002). So far Wahlenbergfjorden is the only fjord-head local- ity in Nordaustlandet where Mytilus has been collected. Its occurrence there is not surprising, however, in view of the more favourable environ- ments characteristic of fjord-head localities in Svalbard (Summerhayes & Elton 1928), coupled with the southward set of the current with the fall- ing tide in Hinlopenstretet (Binney 1926; Mosby 1938; Ślubowska et al. 2005). In particular, the area north of Etonbreen in innermost Wahlenberg- fjorden is known to have the richest terrestrial fl ora in Nordaustlandet (Neilson 1968). In 1958 abundant fragments of Mytilus shells were discovered by the writer and R. Bergström, members of the Swedish Glaciological Expe- dition to Nordaustlandet, on the ground sur- face (in raised beach gravels and sorted circles) inland from Detterbukta and north-east of Lang- grunnodden, the westernmost point of Nordaust- landet. This is the same site that had been visited by the 1861 Swedish expedition. One collection was dated at the then newly-opened laboratory in Uppsala. Following a fairly heavy HCl leach to remove any surface contamination such as sec- ondary calcite crusts, these shells (the innermost 13 % of shell material) yielded a lab-reported age of 9200 ± 190 14C years (U-173; Table 1). This is the age converted to the NBS oxalic acid stand- ard—the original published laboratory age of 9070 ± 190 14C yr BP was based on the Swedish elm standard (Olsson 1960; Olsson et al. 1961; I. U. Olsson, pers. comm. 1961, 1966). The 9070 ± 190 14C yr BP value also was used in the original papers dealing with postglacial emergence (Blake 1961a, 1962; Olsson & Blake 1962), and it is often cited in the literature (e.g. Salvigsen et al. 1992; Salvigsen 2002), but the 9200 year-value is the correct one that should be used for the lab-report- ed age in radiocarbon years (see also Deevey et al. 1967). The next 14 % of shell material yield- ed a lab-reported age of 8530 ± 190 (U-174). The age difference between U-173 and U-174 suggests that this large sample (90 g), collected over a sig- nifi cant area of beaches, was made up of shells of varying age and varying thickness, hence the dis- crepancy between the two dated fractions. With the advent of radiocarbon dating by means of accelerator mass spectrometry (AMS) in the Fig. 3. Inner left valve of Mytilus edulis from the north side of Wahlenbergfjorden, following sampling for 14C age determination. Scale is 1 cm in length. Collected 1924 by K. S. Sandford, Oxford University Expedition. Identifi ed by D. F. W. Baden-Powell (OUM QX 1639). (Photograph by W. Blake, Jr., 26 March 2006.) 128 Mytilis edulis on Nordaustlandet, Svalbard late 1970s, several age determinations have been made on individual fragments of Mytilus, collect- ed by the writer in 1966 on the Stockholm Uni- versity Svalbard Expedition and in 1990 on the Nordaustlandet-90 Expedition. These shells came from the raised beaches in the vicinity of Kinn- vika, at the northern entrance to Murchison fjorden (Figs. 2, 4). They range in age from 8620 ± 90 14C yr BP (Ua-2102; cf. Blake 1995, where the lab- reported age of 9060 ± 90 was used) to 5895 ± 25 14C yr BP (UCIAMS-19834; Table 1). In addition, new analyses of the original collections from the vicinity of Langgrunnodden have been made and these results are reported here as well. As mentioned earlier in this section, and fol- lowing the approach taken by several others in reporting radiocarbon age determinations from Svalbard (Salvigsen et al. 1992; Hjort et al. 1992; Hjort et al. 1995; Koç et al. 2002; Salvigsen 2002; Salvigsen & Høgvard 2005; Ślubowska et al. 2005; all of whom cite Mangerud & Gulliksen 1975), a reservoir effect of –440 years to compensate for the apparent age of seawater has been applied to the 14C ages in Tables 1 and 2 (see footnotes to tables). This value corresponds closely to the 410- year difference if radiocarbon ages on shells are corrected to a δ13C value of 0.0 ‰, which was the practice at the Geological Survey of Canada at the time that shells from Nordaustlandet were dated (Table 2; see Lowdon 1985; Blake 1987). In addi- tion, it is also worth noting that a single intact Buccinum glaciale shell, collected in 1958 amidst the debris of an abandoned Russian trapping hut on Nordre Russøya, Murchisonfjorden (Blake 1961b), yielded an age of 295 ± 70 years (U-122; Olsson 1960). When converted to the NBS oxalic acid standard this age becomes 420 ± 80 14C years (I. U. Olsson pers. comm. 1966), also close to the 440-year value cited above. However, Forman & Polyak (1997), in a sophisticated analysis of pre- bomb molluscs from the Kola Peninsula, Franz Josef Land and Novaya Zemlya, derived reser- voir ages for Franz Josef Land of only 159 ± 50 (GX-19024) and 263 ± 48 years (GX-19026), so the radiocarbon ages from Nordaustlandet even- tually may have to be adjusted as well. Deglaciation chronology At Kinnvika the oldest radiocarbon dated Holo- cene material is a partial shaft of the left humer- us of a polar bear (Ursus maritimus) collect- ed at 72 m a.s.l. and dated at 10 030 ± 110 14C yr BP (Ua-2207). Next oldest, and from the raised beaches proper, a partial right pelvic bone from a bearded seal (Erignathus barbatus) (both iden- tifi ed by C. R. Harington, Canadian Museum of Nature, Ottawa, pers. comm. 1990) at 62 m a.s.l. is 9930 ± 100 14C yr BP (Ua-2099; both in Blake 1996). Applying the same marine correction of –440 years (see Olsson 1980) to these bones yields ages of 9590 ± 110 and 9490 ± 100 14C yr BP for bear and seal, respectively (Table 2). On the opposite, south side of Murchisonfjorden, Mya truncata shells at 82 m have yielded lab-report- ed ages of 11 180 ± 190 14C yr BP (U-2095) and 11 150 ± 110 14C yr BP (U-660; both in Olsson et al. 1969; Blake 1981; Hoppe 1987), but note that Karlén (1994) places the highest marine limit in this area at 67 m a.s.l. These results become 10 740 ± 190 and 10 710 ± 110, respectively, when the –440 year correction is applied. Also, a drift- wood log (Larix sp.) at 36.5 m elevation near Sveanor (Kulling 1936), in the vicinity, has pro- vided age determinations from two laboratories: 9400 ± 140 (U-70; converted to the NBS oxalic acid standard; Olsson 1959; Deevey et al. 1967) and 9420 ± 100 (GSC-3490; Blake 1987). These results from wood reinforce the 14C ages of bones and shells as well as the age of the basal organic sediments in Krystallvatnet, 10 000 ± 600 14C yr BP (U-92; converted to the NBS oxalic acid stand- ard), some 8 km to the east–north-east of Sveanor (Olsson 1960; Häggblom 1963). Individuals of the Mytilus edulis complex thus appeared some 900 to 1000 14C years after the earliest mammals were recorded at Kinnvika or, assuming that the early ages of shells are correct, roughly 2000 14C years after the sea fi rst entered Murchisonfjorden some 10 km to the south of Kinnvika. Ages between 9500 and 9000 14C years BP on marine pelecypod shells are recorded for the initial incursion of the sea into the heads of nearby fjords such as Wahlenbergfjorden and Lady Frank lin fjorden, slightly earlier at Dalvå- gen (where Chlamys islandica and Balanus bal- anus were dated as well as Hiatella arctica) near the northern tip of Nordaustlandet (Table 2; also Blake 1987, 1989). Elsewhere on Nordaustland- et, driftwood at 22 m a.s.l. near the northern tip of Prins Oscars Land dates from 9465 ± 120 14C yr BP (St-7989; Karlén 1987), and Mya trunca- ta shells from a river section south of the head of Rijpfjorden are 9100 ± 140 14C yr BP (GSC-2669; Blake 1981, 1987). Further east, the earliest radio- carbon age for the raised beaches on Storøya, an 129Blake 2006: Polar Research 25(2), 123–137 Table 2. Selected early Holocene radiocarbon ages, Nordaustlandet, Svalbard. (Table continues next page.) Field no. Elev. (m) Lab. no. a Age, reported by lab. Age, corrected for apparent age of seawater γ13C (PDB) ‰ Comments and collector b Kinnvika, Murchisonfjorden WB-90-21A 72 Ua-2207 10 030 ± 110 9590 ± 110 c –21.0(assumed) Partial shaft of left humerus of a polar bear (Ursus maritimus). 9.3 g. W. Blake, Jr. WB-90-11 62 Ua-2099 9930 ± 100 9490 ± 100 c –21.0(assumed) A right pelvic bone from a bearded seal (Erignathus barbatus). 12.6 g. W. Blake, Jr South side of Murchisonfjorden H/131-135 62 U-92 10 000 ± 600 — –32.0 Krystallvatnet—limnic peat at 131 - 134 (or 118 - 122) cm depth in core. Water depth 19 m. A. Häggblom. WB-58-27 36.5 U-70 9400 ± 140 — –24.0 Larix sp. log near Sveanor. W. Blake, Jr. WB-58-27 36.5 GSC-3490 9420 ± 100 — –25.7 Same log, 11.7 g dry wood. One 4-day count in 5-L counter. — 82 U-2095 11 180 ± 190 10 740 ± 190 0.3 Numerous Mya truncata shells, partly buried in beach material. Innermost 35 % of shell material. M. G. Grosswald. — 82 U-660 11 150 ± 110 10 710 ± 110 0.3(assumed) Shell layer surrounding U-2095 corresponds to 40 % of shell material. Outermost 25 % removed by HCl leach. Lady Franklinfjorden—Søre Franklinbreen WB-167-66 125-130 Ua-905 9525 ± 130 9085 ± 130 — Pelecypod shell fragment, probably Chlamys islandica. Calcite. 0.008 g. No leach. W. Blake, Jr. WB-167-66 125-130 Ua-1058 9675 ± 140 9235 ± 140 — Unidentifi ed pelecypod shell fragment. Aragonite. 0.16 g. Outermost 50 % removed by HCl leach. Dalvågen WB-41-66 18 GSC-2729 9670 ± 200 9670 ± 200 2.6 Chlamys islandica (intact pair), same site. Outermost 10 % of shell removed by HCl leach. Calcite, aragonite and rhodocrosite 10.25 g. WB-41-66 18 Ua-341 9950 ± 200 9510 ± 200 — Chlamys islandica (single fragment), same site. Cal-cite. 0.04 g. Innermost 5 % of shell used for dating. WB-64-66 23 Ua-902 9720 ± 115 9280 ± 115 — Balanus balanus Calcite. 0.07 g. Inner 50 % of shell used for dating. W. Blake, Jr. North end Prins Oscars Land, near Arkvatnet — 22 St-7989 9465 ± 120 — –26.8 Driftwood log. H. Österholm & V. Schytt. Rijpdalen WB-120-66 32-36 GaK-1915 9200 ± 180 9200 ± 180 — Mya truncata shells in river section, south of the head of Rijpfjorden. 47.0 g. W. Blake, Jr. WB-120-66 32-36 GSC-2669 9100 ± 140 9100 ± 140 0.3 Mya truncata shells in river section, same site. Outer most 20 % of shell removed by HCl leach. 26.9 g. Wahlenbergfjorden WB-187-66 ∼43 GSC-2736 9670 ± 140 9670 ± 140 3.6 Single right valve of Mya truncata. Outermost 10 % of shell removed by HCl leach. Aragonite. 12.0 g. Marine limit at ∼66 m. W. Blake, Jr. 130 Mytilis edulis on Nordaustlandet, Svalbard island east of Nordaustlandet, is 9685 ± 125 14C yr BP (St-7825, Jonsson 1983; also reported uncor- rected for δ13C in Häggblom 1982a, 1982b). This result was obtained on a driftwood log at 53.3 m a.s.l. The beach at this level, as with all other raised beaches on Storøya, disappears under the ice cap that occupies the southern half of the island, showing that the ice cap has developed, again, in latest Holocene time (Schytt 1981). At Svartknausfl ya, south-western Nordaustlandet, wil low wood at 65.5 m a.s.l. dates from 9550 ± 80 14C yr BP (T-2503; Salvigsen 1978, 1979). It is thus clear that by 9500 to 9000 14C yr BP, coasts all around Nordaustlandet had become free of glacier ice. However, with the exception of inner- most Wahlenbergfjorden, M. edulis has not been found at any of these locations. Nor was any trace of Mytilus found at the other north coast sites vis- ited in the wide-ranging 1966 surveys carried out by the writer, namely at Lady Franklin fjorden, Lindhagenbukta, Sabinebukta, Rijp fjorden, Zorg- drager fjorden, Finn Malmgrenfjorden, Søre Rep- øya, and Sjuøyane (Fig. 1). Data from Hinlopenrenna, the trough across the continental shelf to the north of Hinlopen- stretet and north-west of Nordaustlandet, are as follows: 1) shells of Chlamys islandica ca. 1.2 m below the seabed and above coarse sedi- ments interpreted as glaciomarine in core PO 78- 17 (80° 11' N, 16° 40' E; 205 m water depth), some 17.5 km north-west of Langgrunnodden, are 9010 ± 140 14C yr BP (T-3103; Salvigsen & Nydal 1981); and 2) where Hinlopenrenna intersects the edge of the continental shelf, ca. 36.5 km north- west of Langgrunnodden, benthic foraminifera at 690 - 699 cm in core NP 94-51SC2 (80° 21.35' N, 16° 17.970' E, 400 m water depth) are 13 725 ± 135 14C yr BP (TUa-3587; Koç et al. 2002; this age is listed in uncorrected form as 14 162 ± 135 14C yr BP in Ślubowska et al. 2005). Discussion Oceanographic conditions and glacier recession With regard to the question of lower and more variable salinity in coastal waters, proposed by Feder et al. (2003) as important to the distribution of Mytilus in northern Alaska, a few observations are pertinent. As shown in Fig. 2, the north-west corner of Nordaustlandet, between Kinnvika and Langgrunnodden, has an intricate and low-lying coastline, developed in carbonate rocks of the Roaldtoppen Group (Flood et al. 1969; Sandelin et al. 2001). This gently shelving coast, character- ized by the presence of numerous shoals (Binney 1926), lagoons and both bay-head and bay-mouth bars, is the area where all of the writer’s col- Field no. Elev. (m) Lab. no. a Age, reported by lab. Age, corrected for apparent age of seawater δ13C (PDB) ‰ Comments and collector b Storøya 7 53.3 St-7825 9685 ± 125 — –26.4 Driftwood log. A Häggblom. Svartknausfl ya 30 65.5 T-2503 9550 ± 80 — — Salix sp. wood 1 m long on ground surface. O. Salvigsen. a Laboratory designations: U = Uppsala; Ua = Tandem Accelerator Laboratory, Uppsala; St = Natural History Museum, Stockholm; GaK = Gakushuin University, Japan; GSC = Geological Survey of Canada, Ottawa; T = Trondheim. See footnote d, Table 1, with regard to Gakushuin results. Laboratory reported ages from U, Ua, St and T are normalized to a base of δ13C = –25.0 ‰. Marine shell samples processed at GSC and GaK are corrected to δ13C = 0.0 ‰, so no additional correction is applied (Lowdon 1985; Blake 1987; Kigoshi et al. 1963). b Identifi cations of bones: C. R. Harington, Canadian Museum of Nature, Ottawa; shells: W. Blake, Jr., Geological Survey of Canada, Ottawa (except for U-2095); driftwood from Sveanor: G. W. Burns, Ohio Wesleyan University, Delaware, OH c Here the same correction (–440 years) is used as for marine molluscs. Håkansson (1974) reports an apparent age of 480 ± 70 years (Lu-715) for the cranium of a young polar bear collected in 1989 in inner Isfjorden, but time of death is estimated at 50 ± 50 years. Thus the “apparent age” for mammals whose diet is marine organisms may have to be modifi ed when additional data become available. Table 2, continued from previous page. 131Blake 2006: Polar Research 25(2), 123–137 lections of Mytilus have been made. No signifi - cant rivers reach this part of the coast. Early in Holocene time, when the peninsulas now exposed because of glacial rebound would have been beneath the sea, conditions closer to full marine might have prevailed, as they do offshore today under the infl uence of North Atlantic Water of the Atlantic Current (Loeng 1991). This Atlantic Layer is conveyed northward and then eastward by a strong boundary current, the West Spitsber- gen Current. North of Hinlopenstretet the core of the Atlantic Layer occurs at 100 to 400 m depth, with temperatures of 3 to 4.5 °C and salinities of 34.4 to 35.0 ‰ (Koç et al. 2002; Ślubowska et al. 2005; see also Fig. 2 in Peacock 1989). Further- more, under early Holocene conditions of rapid rebound, there would have been little time avail- able for lagoons and bars to develop. Some 9200 to 8700 14C yr BP and perhaps until ca. 1000 14C yr BP (Blake 1987, 1989), the front of Søre Franklinbreen at the head of Lady Franklin- fjorden is known to have been several kilometres behind (south-east of) the various positions that it has occupied since 1899 (De Geer 1923; Moss & Glen 1939; Blake 1962, 1989). That is, at the time that Mytilus reached the north-west coast of Nordaustlandet, this major source of freshwater would have been even more distant from Lang- grunnodden and Kinnvika than it is today, if in fact this outlet glacier continued to exist at all. In this connection Koerner concluded that the Svalbard ice caps, among others, “consist entire- ly of Holocene ice indicating that their re-growth began during some part of the Holocene, as the climate cooled” (1999: 81). Nonetheless, the yearly melting of sea ice, plus runoff from the land, clearly must have resulted in at least some temporary reduction in salinity in the shallow water along the outermost coasts where Mytilus has been found in considerable abundance on the raised beaches. But were the waters any less saline at that time than they are today, and what effect did any changes in salin- ity have on the abundance of predators (cf. Feder et al. 2003)? As an example of conditions during the International Geophysical Year (1957–58), on 18 July 1957, the Finnish ship RV Aranda occu- pied Hydrographic Station No. 35 in Kinnvika, Murchisonfjorden (80° 03' N, 18° 15' E). Salini- ties and water temperature were as follows: sur- face (33.96 ‰; 2.67 °C); 10 m depth (34.39 ‰; 2.01 °C), 15 m depth (34.44 ‰; 1.88 °C) and 20 m depth (34.48 ‰; 1.78 °C; Hela & Koroleff 1958). Yet no evidence has been found by the writer that Kinnvika harbours Mytilus edulis today, either as living colonies or individuals cast up on the modern beaches attached to marine algae. The same is true for the Langgrunnodden–Detter- bukta area. Also, the Mytilus collections from the raised beaches in these areas showed no evidence of drilling by naticid or other predatory snails. The confi guration of Wahlenbergfjorden is very different from the topography of the outer coast between Kinnvika and Langgrunnodden. The 40 to 45 km long Wahlenbergfjorden extends deeply into Nordaustlandet, reaching close to the geographical centre of the island (Fig. 1). Gla- ciers enter the head of the fjord from high land to the north, east and south, and rivers drain- ing the southern half of Rijpdalen, as well as the adjacent ice caps, provide additional freshwa- ter. Some 7400 to 6900 14C yr BP, when Mytilus lived at the head of the fjord, that area still would have received signifi cant runoff from the land even though the ice caps and glaciers were much reduced in size, or perhaps absent. Basic oceanographic data for Hinlopenstretet and Wahlenbergfjorden, plus some information for Murchisonfjorden, were provided by Mosby (1938), as a result of his work aboard Quest during the course of the Swedish–Norwegian Arctic Expedition in the summer of 1931. Hydrographic stations on both the north and south sides of Søre Russøya (24 and 30 June, respectively), yielded salinities in the 33.84 to 34.29 ‰ range with most temperatures slightly negative at depths between 0 and 25 m (Mosby 1938, Table 1). Mosby noted with regard to Murchisonfjorden, “It thus appears that these waters are extensively diluted by melt- ing water from land, from the glaciers” (p. 61). Fig. 4. Typical occurrence of Mytilus fragment (arrow) in beach gravel at Kinnvika; part of sample WB-90-25 at 5.1 m a.s.l. (Table 1). Knife for scale is 9 cm in length. (Photograph by W. Blake, Jr., 27 July 1990.) 132 Mytilis edulis on Nordaustlandet, Svalbard Data for 10 hydrographic stations spread over the length of Hinlopenstretet were also presented: at Station 94, west of Langgrunnodden, the surface water had a salinity of 33.57 ‰ on 17 August 1931, and the values increased progressively with depth to a maximum of 34.98 ‰ at 200 m; temperatures ranged between 3.45 and 5.13 °C. Mosby (1938) also stressed the fact that salinities at the most easterly stations (6 and 7) in Wahlenbergfjorden were lower (all < 34.0 ‰ at 0 to 10 m depth, with negative temperatures throughout) than at Station 13 in Hinlopenstretet outside the mouth of the fjord (due south of Brageneset; see Fig. 1), where all salinity values were above 34.0 ‰ and temper- atures ranged between –0.89 and 0.71 °C (0 to 250 m depth, 3–4 July 1931). Although Mosby does not comment with regard to the salinities in inner Wahlenbergfjorden, presumably the same con- clusion can be reached that he did for Murchison- fjorden. According to Peacock (1993), M. edulis, in open sea conditions at the northern limit of its distribution, requires a minimum summer sea surface temperature of 4 °C. Palaeoceanographic implications The age determinations on Mytilus shells from north-western Nordaustlandet show that this pelecypod lived north of the 80th parallel for much of the fi rst half of Holocene time. The arrival of Mytilus to Nordaustlandet coincided with the fi rst infl ux of subpolar North Atlantic Water record- ed in core PCM7 (78° 37' N, 7° 54' E) at 1073 m depth off the west coast of Spitsbergen (Lloyd et al. 1996). These authors state: “This initial period of subpolar water infl uence along the Spitsber- gen margin lasted until approximately 9 ka...” (p. 297). The information gleaned from this core agrees with the earlier conclusion by Svendsen & Mangerud (1992) that a phase of rapid glacial retreat in the inner fjords of Spitsbergen and in eastern Svalbard occurred at the beginning of the Holocene. Farther south, off the western Barents shelf at 75° N, Sarnthein et al. (2003) calculated that the major postglacial warming of the West Spitsbergen Current, by 4 to 5 °C, occurred in early Holocene time. Salvigsen (2002) has suggested that Mytilus was most widespread in Svalbard at ca. 7250 14C yr BP, a conclusion based in part on the one age determination available to him from Wahl- enbergfjorden. Had more extensive and more detailed collections been made in north-western Nordaustlandet, with a whole series of sub-col- lections selected across the altitudinal range at which the shells occur at each site, and if a sig- nifi cantly greater number of age determinations had been carried out, it might have been possible to determine with certainty whether Mytilus lived along Hinlopenstretet continuously for some 3000 years or whether it colonized the island on more than one occasion. The series of 14 radiocarbon ages on Mytilus shells from the Hiorthfjellet fan delta, on Spitsbergen, ranging from 6175 ± 90 (T- 13345) to 4350 ± 110 (T-13358) 14C yr BP (Lønne & Nemec 2004), for example, clearly shows the continuous presence of Mytilus at this site on the south side of Isfjorden. On the northern coast of Spitsbergen Mytilus had appeared by ca. 9300 14C years BP (Salvig- sen & Österholm 1982; Brückner & Halfar 1994; Salvigsen 2002), that is, slightly earlier than on Nordaustlandet. Then Mytilus persisted in north- ern Spitsbergen for another 500 years—until ca. 5300 14C yr BP (Salvigsen 2002)—in the inner- most, southern part of one of the main, north coast fjords. Nearly all of the ages on Mytilus from Nordaustlandet fall within the interval of ca. 8800 to 5000 14C yr BP when this species also was present on Edgeøya, in south-eastern Sval- bard (Hjort et al. 1992; Hjort et al. 1995). The interval from ca. 8000 to 4000 14C yr BP is the time when the mean July temperatures in outer Isfjorden, based on the analysis of macrofossils in lake sediments, may have been at least 1.5 °C higher than today (Birks 1991). In addition, the interval from 8400 to 4900 14C yr BP corresponds to the time when six Boreal mollusc species col- onized a section of the West Greenland coast between 65° 30' N and 68° 30' N (Funder & Fred- skild 1989; Funder & Weidick 1991), and a sim- ilar interval of roughly 8000 to 5500 14C yr BP for colonization by Mytilus was reported from the central East Greenland coast by Hjort & Funder (1974). These authors suggested that Mytilus may have reached central East Greenland via a branch of the West Spitsbergen Current, which brought warm Atlantic water to the coast at a time when the cold polar East Greenland Current was dimin- ished in strength. This hypothesis is supported by an analysis of stable isotope composition of water samples and bivalve shells in East Greenland. Israelson & Buchardt concluded that: “A higher salinity in Scoresby Sund and in the coastal waters of Germania Land in 133Blake 2006: Polar Research 25(2), 123–137 the early Holocene has been demonstrat- ed. This is in agreement with the studies of Hjort & Funder (1974) who postulated that the immigration of Mytilus edulis to the East Greenland fjords during this time was connected with an infl uence of Atlantic Water, more saline than the present coastal waters of East Greenland” (1991: 121–122). Further, Dyke et al. (1996) note that a shift west- ward in the Transpolar Drift may result in both the East and West Greenland Currents becoming warmer. Comparison with Baffi n Bay An analogous situation to Nordaustlandet exists in northernmost Baffi n Bay. In 1940 M. edulis was found living intertidally at North Star Bugt in the Thule District, North-west Greenland (ca. 76° 30' N; Vibe 1950). Later, in 1968, living indi- viduals of Mytilus were collected at several addi- tional sites in the Thule District and, in 1973, far- ther north at Siorapaluk in Robertson Fjord (ca. 77° 46' N), where these pelecypods were used by the local population as food (Theisen 1973). By contrast, no living Mytilus or fossil shells have been found on the Ellesmere Island side of northernmost Baffi n Bay at similar latitudes (Dale 1985; Blake 1992, 1993). However, near the southern end of Coburg Island (75° 52.5' N), at the entrance to Jones Sound and some 40 km from Devon Island, Mytilus was collected from a coast- al section by the writer in 1970 and 1972. Two radiocarbon age determinations were made on these shells: the blue, outer prismatic layer (cal- cite) yielded an age of > 38 000 14C yr BP (GSC- 1425; Blake 1973), whereas the inner nacreous material (aragonite) from the same shells, dated later by AMS, yielded an age of 46 070 ± 830 14C yr BP (TO-3991). No Mytilus shells were discov- ered in the richly fossiliferous Holocene strata overlying the “old” shells, nor were any modern shells of this species found along the present- day shores of Coburg Island or along the south- ern coast of Ellesmere Island. On the Green- land side, by contrast, both pre-Holocene and Holocene occurrences of Mytilus are known from the North Star Bugt area, Thule District (Davies et al. 1963; Blake 1975; Funder & Fredskild 1989; Funder 1990). These northern occurrences of Mytilus along the Baffi n Bay coast of Greenland are a consequence of the northward fl owing warm water of the West Greenland Current which, like the West Spitsbergen Current in Svalbard, car- ries the pelagic Mytilus larvae northward. In the case of Greenland, the pelagic larvae originate in southern West Greenland, where Mytilus is wide- spread (Madsen 1936; Funder & Símonarson 1984), whereas in Svalbard, the larvae presum- ably originate in northern Norway (Berge et al. 2005; Berge et al. 2006). On the Canadian side of Baffi n Bay, cooled by the southward fl owing Baffi n Current (Funder 1990), recent Mytilus has not been found north of the Pond Inlet area, northern Baffi n Island, at approximately 72° 41' N, some 500 km south-west of the Thule District and 350 km south of Coburg Island (Nichols 1936; Laursen 1946; Ellis 1955; Lubinsky 1980). Radiocarbon age determinations of Mytilus collected from the modern beach near the hamlet of Pond Inlet in 1963 by B. G. Craig were 80 ± 220 and 340 ± 90 14C yr BP (GSC-1570 and -1898, respectively); another sample collected in roughly the same area in 1923 yielded an age of 1210 ± 330 14C yr BP (GSC-1583; all in Blake 1987). The occurrence of Mytilus at this lati- tude results from the counter-clockwise circula- tion which brings the warmer waters of the West Greenland Current to the west side of northern Baffi n Bay (Kiilerich 1939; Dunbar 1972; Funder 1990; Funder & Weidick 1991). Mytilus shells of Holocene age, based on stratigraphy, also have been found in the vicinity of Pond Inlet. To the west shells were found in a river-cut section at about 15 m a.s.l. (Klassen 1993), and to the east shell fragments were found among rounded peb- bles on a raised beach at about 26 m a.s.l. (D. A. Hodgson pers. comm. 2006). Conclusions The timing of the arrival of Mytilus in north- western Nordaustlandet agrees with the propos- al by Lloyd et al. (1996) that the fi rst penetration of subpolar North Atlantic waters occurred off the western margin of Spitsbergen at the begin- ning of the Holocene. According to their results, based on a study of two cores, “the faunal data suggest this period, until approximately 9 ka BP, was as warm if not warmer than the present day along the Spitsbergen margin” (p. 299). The dras- tic warming in early Holocene time, well docu- mented from ice caps as far afi eld from Svalbard as Arctic Canada (Koerner & Fisher 1990, 1995, 134 Mytilis edulis on Nordaustlandet, Svalbard 2002), resulted in rapid recession of glaciers all around Nordaustlandet and probably caused the disappearance, or near disappearance, of the ice caps on this island. This same warming allowed mussels of the M. edulis complex to colonize the coasts of Spitsbergen via the West Spitsbergen Current, reaching north-western Nordaustland- et by 9000 14C yr BP. The lower salinities which resulted from the massive melt-off of glaciers may have played a role in the spread of Mytilus along the coasts of Svalbard in early Holocene time, but the warming and intensity of the West Spitsbergen Current itself must be regarded as the driving force. On the basis of their study of core NP94-51SC2 in Hinlopenrenna, only 36.5 km north-west of Langgrunnodden, the northernmost site where Mytilus was collected, Ślubowska et al. (2005) conclude that: “During the late Holocene the infl ow of warm water masses carried by the West Spitsbergen Current decreased to a very low level. Conditions at the surface and bottom water were polar with low salini- ty and extensive sea ice cover and marked by the readvance of glaciers on Svalbard” (2005: 13). This statement is consistent with the evidence presented here for the disappearance of Mytilus from Nordaustlandet after ca. 5800 14C yr BP. Acknowledgements.—The writer’s participation in the expedi- tions to Nordaustlandet was made possible by grants from the Foreign Field Research Program, National Academy of Sci- ences—National Research Council (1957 and 1958) and from the Arctic Institute of North America (1966). In both cases funds were provided by the US Offi ce of Naval Research. Other major funding for these expeditions, as well as that in 1990, came from the Swedish Natural Science Research Council), the Swedish Society for Anthropology and Geogra- phy, the Swedish Polar Research Secretariat and the Nation- al Geographic Society (grant no. 4068-89). Logistical sup- port was provided by the Finnish Institute of Marine Research (Aranda), the Swedish Navy (Älvsnabben, under Kommendör- kapten, now Amiral, B. Lundvall, ret.), both Norwegian and Swedish Air Forces, the Offi ce of the Governor of Svalbard and the Norwegian Polar Institute (T. Gjelsvik & K. Z. Lun- dquist; ships Sjøvern and Minna). Helicopter support in 1966 was provided by a contingent from the Swedish Army (Major B. Hasselrot), and the Norwegian Coast Guard (KV Senja) put out a fuel depot for the 1990 expedition. Excellent assistance in the fi eld was provided by R. Bergström (1958) and H. Bill- eström (1966). The joint leader in 1990, Professor W. Karlén, as well as E. Skye, P.-O. Isaksson and K. Gjerde, all helped with levelling. I am particularly indebted to the late professors V. Schytt, G. Hoppe & G. H. Liljequist for making it possible for me to participate in these expeditions and for their sustained interest and support over several decades. P. Jeffery, Assistant Curator of Geology at the Oxford University Museum of Natural His- tory, kindly arranged for the loan of K. S. Sandford’s samples from Wahlenbergfjorden. Radiocarbon dating was carried out at laboratories as indicated; special thanks go to I. U. Olsson and G. Possnert at their respective laboratories in Uppsala, J. A. Lowdon (Geological Survey of Canada, Ottawa) and J. Southon (University of California at Irvine). H. F. Aas, at the Norwegian Polar Institute, was helpful in connection with the aerial photograph. H. M. Feder, Institute of Marine Research, and D. W. Norton, School of Fisheries and Ocean Science, both University of Alaska at Fairbanks, provided good dis- cussion about Mytilus as well as perceptive remarks on the manuscript. In addition, valuable comments and suggestions for improvement have been made by the journal referees: S. Bondevik, University of Tromsø; S. Funder, Geological Museum, University of Copenhagen; and C. Hjort, Universi- ty of Lund. O. Salvigsen, University of Oslo, called my atten- tion to several pertinent issues of Svalbardposten. At the Geo- logical Survey of Canada, T. Barry prepared the illustrations, S. Parnham processed the manuscript and D. A. Hodgson pro- vided a most helpful internal review. This article is Geologi- cal Survey of Canada Contribution 2005696. References Berge, J., Johnsen, G., Nilsen, F., Gulliksen, B. & Slagstad, D. 2005: Ocean temperature oscillations enable reappearance of blue mussels Mytilus edulis to Svalbard after a 1000 year absence. Mar Ecol. Prog. Ser. 303, 167–175. 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