(Table 1) Cover of shrub and tree species, and number of stems (>=3.5 cm DBH) during 1976-1977 and 2009-2010, respectively

Shrubs and trees are expected to expand in the sub-Arctic due to global warming. Our study was conducted in Abisko, sub-arctic Sweden. We recorded the change in coverage of shrub and tree species over a 32- to 34-year period, in three 50 x 50 m plots; in the alpine-tree-line ecotone. The cover of shrubs and trees (<3.5 cm diameter at breast height) were estimated during 2009-2010 and compared with historical documentation from 1976 to 1977. Similarly, all tree stems (>=3.5 cm) were noted and positions determined. There has been a substantial increase of cover of shrubs and trees, particularly dwarf birch (Betula nana), and mountain birch (Betula pubescens ssp. czerepanovii), and an establishment of aspen (Populus tremula). The other species willows (Salix spp.), juniper (Juniperus communis), and rowan (Sorbus aucuparia) revealed inconsistent changes among the plots. Although this study was unable to identify the causes for the change in shrubs and small trees, they are consistent with anticipated changes due to climate change and reduced herbivory.

Halogene concentrations and iodine isotopic composition in pore water on Hydrare Ridge, Cascadia continental margin

We report iodine and bromine concentrations in a total of 256 pore water samples collected from all nine sites of Ocean Drilling Program Leg 204, Hydrate Ridge. In a subset of these samples, we also determined iodine ages in the fluids using the cosmogenic isotope 129I (T1/2 = 15.7 Ma). The presence of this cosmogenic isotope, combined with the strong association of iodine with methane, allows the identification of the organic source material responsible for iodine and methane in gas hydrates. In all cores, iodine concentrations were found to increase strongly with depth from values close to that of seawater (0.0004 mM) to concentrations >0.5 mM. Several of the cores taken from the northwest flank of the southern summit show a pronounced maximum in iodine concentrations at depths between 100 and 150 meters below seafloor in the layer just above the bottom-simulating reflector. This maximum is especially visible at Site 1245, where concentrations reach values as high as 2.3 mM, but maxima are absent in the cores taken from the slope basin sites (Sites 1251 and 1252). Bromine concentrations follow similar trends, but enrichment factors for Br are only 4-8 times that of seawater (i.e., considerably lower than those for iodine). Iodine concentrations are sufficient to allow isotope determinations by accelerator mass spectrometry in individual pore water samples collected onboard (~5 mL). We report 129I/I ratios in a few samples from each core and a more complete profile for one flank site (Site 1245). All 129I/I ratios are below the marine input ratio (Ri = 1500x10**-15). The lowest values found at most sites are between 150 and 250x10**-15, which correspond to minimum ages between 40 and 55 Ma, respectively. These ages rule out derivation of most of the iodine (and, by association, of methane) from the sediments hosting the gas hydrates or from currently subducting sediments. The iodine maximum at Site 1245 is accompanied by an increase in 129I/I ratios, suggesting the presence of an additional source with an age younger than 10 Ma; there is indication that younger sources also contribute at other sites, but data coverage is not yet sufficient to allow a definitive identification of sources there. Likely sources for the older component are formations of early Eocene age close to the backstop in the overriding wedge, whereas the younger sources might be found in recent sediments underlying the current locations of the gas hydrates.

Mesozooplankton biomass data from Disko Bay, West Greenland, 2008

The study site was located in the Disko Bay off Qeqertarsuaq, western Greenland. Due to land-connected sea ice coverage during winter, 2 sampling sites were combined. At the first site in winter (21 February to 23 March 2008), sampling was conducted through a hole in the ice at ca. 65 to 160 m depth approximately 0.5 nautical mile (n mile) south of Qeqertarsuaq (69° 14' N, 53° 29' W). In spring and summer (9 April to 18 July), sampling was done at a monitoring station 1 n mile south from Qeqertarsuaq (69° 14' N, 53° 23' W) at 300 m depth. Sampling was carried out between 10:00 and 17:00 h. During sampling from the ice, mesozooplankton was collected using a modified WP-2 net (45 µm) equipped with a closing mechanism (Hydrobios). Samples were collected in 3 depth strata (0-50, 50-100, and 100-150 m). During ship-based sampling, mesozooplankton was collected with a multinet (50 µm) equipped with a flow meter (Multinet, Hydrobios type midi), and 2 additional depth strata (150-200m and 200-250 m) were included. In addition to the seasonal study one diurnal investigation with sampling every 6 h was conducted from 29 April at 12:00 h to 30 April 30 at 12:00 h. Samples were immediately preserved in buffered formalin (5% final concentration) for later analyses. Biomass values of the different copepod species were calculated based on measurements of prosome length, and length/weight relationships. Two regressions for Calanus spp. were established for biomass calculations: one applicable prior to and during the phytoplankton bloom until 4 May, and another from 9 May onwards.

Response of three krill species to hypoxia and warming: An experimental approach to oxygen minimum zones expansion in coastal ecosystems

To understand the adaptation of euphausiid (krill) species to oxygen minimum zones (OMZ), respiratory response and stress experiments combining hypoxia/reoxygenation exposure with warming were conducted. Experimental krill species were obtained from the Antarctic (South Georgia area), the Humboldt Current system (HCS, Chilean coast), and the Northern California Current system (NCCS, Oregon). Euphausia mucronata from the HCS shows oxyconforming or oxygen partial pressure (pO2)-dependent respiration below 80% air saturation (18 kPa). Normoxic subsurface oxygenation in winter posed a "high oxygen stress" for this species. The NCCS krill, Euphausia pacifica, and the Antarctic krill, Euphausia superba maintain respiration rates constant down to low critical pO2 values of 6 kPa (30% air saturation) and 11 kPa (55% air saturation), respectively. Antarctic krill had the lowest antioxidant enzyme activities, but the highest concentrations of the molecular antioxidant glutathione (GSH) and was not affected by 6 h exposure to moderate hypoxia. Temperate krill species had higher SOD (superoxide dismutase) values in winter than in summer, which relate to higher winter metabolic rate (E. pacifica). In all species, antioxidant enzyme activities remained constant during hypoxic exposure at habitat temperature. Warming by 7°C above habitat temperature in summer increased SOD activities and GSH levels in E. mucronata (HCS), but no oxidative damage occurred. In winter, when the NCCS is well mixed and the OMZ is deeper, +4°C of warming combined with hypoxia represents a lethal condition for E. pacifica. In summer, when the OMZ expands upwards (100 m subsurface), antioxidant defences counteracted hypoxia and reoxygenation effects in E. pacifica, but only at mildly elevated temperature (+2°C). In this season, experimental warming by +4°C reduced antioxidant activities and the hypoxia combination again caused mortality of exposed specimens. We conclude that a climate change scenario combining warming and hypoxia represents a serious threat to E. pacifica and, as a consequence, NCCS food webs.

Mesozooplankton size data from Disko Bay, West Greenland, 2008

The study site was located in the Disko Bay off Qeqertarsuaq, western Greenland. Due to land-connected sea ice coverage during winter, 2 sampling sites were combined. At the first site in winter (21 February to 23 March 2008), sampling was conducted through a hole in the ice at ca. 65 to 160 m depth approximately 0.5 nautical mile (n mile) south of Qeqertarsuaq (69° 14' N, 53° 29' W). In spring and summer (9 April to 18 July), sampling was done at a monitoring station 1 n mile south from Qeqertarsuaq (69° 14' N, 53° 23' W) at 300 m depth. Sampling was carried out between 10:00 and 17:00 h. During sampling from the ice, mesozooplankton was collected using a modified WP-2 net (45 µm) equipped with a closing mechanism (Hydrobios). Samples were collected in 3 depth strata (0-50, 50-100, and 100-150 m). During ship-based sampling, mesozooplankton was collected with a multinet (50 µm) equipped with a flow meter (Multinet, Hydrobios type midi), and 2 additional depth strata (150-200m and 200-250 m) were included. In addition to the seasonal study one diurnal investigation with sampling every 6 h was conducted from 29 April at 12:00 h to 30 April 30 at 12:00 h. Samples were immediately preserved in buffered formalin (5% final concentration) for later analyses. Biomass values of the different copepod species were calculated based on measurements of prosome length, and length/weight relationships. Two regressions for Calanus spp. were established for biomass calculations: one applicable prior to and during the phytoplankton bloom until 4 May, and another from 9 May onwards.

(Table 1) Nesting characteristics of greater snow geese (Chen caerulescens atlanticus) on Bylot Island between 1995-2005

1. Habitat heterogeneity and predator behaviour can strongly affect predator-prey interactions but these factors are rarely considered simultaneously, especially when systems encompass multiple predators and prey. 2. In the Arctic, greater snow geese Anser caerulescens atlanticus L. nest in two structurally different habitats: wetlands that form intricate networks of water channels, and mesic tundra where such obstacles are absent. In this heterogeneous environment, goose eggs are exposed to two types of predators: the arctic fox Vulpes lagopus L. and a diversity of avian predators. We hypothesized that, contrary to birds, the hunting ability of foxes would be impaired by the structurally complex wetland habitat, resulting in a lower predation risk for goose eggs. 3. In addition, lemmings, the main prey of foxes, show strong population cycles. We thus further examined how their fluctuations influenced the interaction between habitat heterogeneity and fox predation on goose eggs. 4. An experimental approach with artificial nests suggested that foxes were faster than avian predators to find unattended goose nests in mesic tundra whereas the reverse was true in wetlands. Foxes spent 3-5 times more time between consecutive attacks on real goose nests in wetlands than in mesic tundra. Their attacks on goose nests were also half as successful in wetlands than in mesic tundra whereas no difference was found for avian predators. 5. Nesting success in wetlands (65%) was higher than in mesic tundra (56%) but the difference between habitats increased during lemming crashes (15%) compared to other phases of the cycle (5%). Nests located at the edge of wetland patches were also less successful than central ones, suggesting a gradient in accessibility of goose nests in wetlands for foxes. 6. Our study shows that the structural complexity of wetlands decreases predation risk from foxes but not avian predators in arctic-nesting birds. Our results also demonstrate that cyclic lemming populations indirectly alter the spatial distribution of productive nests due to a complex interaction between habitat structure, prey-switching and foraging success of foxes.

(Table 1) Correlation of precipitation and winter mass balance (bw) at Storbreen, Norway

Measurements of winter balance (bw) and summer balance (bs) have been carried out at Storbreen since 1949. Here we apply a simple mass balance model to study the climate sensitivity and to reconstruct the mass balance series prior to 1949. The model is calibrated and validated with data from an automatic weather station (AWS) operating in the ablation zone of Storbreen since 2001. Regression analysis revealed that bw was best modelled using precipitation data southwest of the glacier. Results from the model compared well with reported mass balance values for the period 1949-2006, obtained correlations (r) for bw and bs varied between 0.83 and 0.87 depending on model set up. Reconstruction of the mass balance series for the period 1924/1925-1948/1949 suggested a cumulative mass deficit of c. 30 m w.e. mainly due to highly negative summer balances, but also lower bw than the average for 1949-2006. Calculated change in specific mass balance for a ±1°C change in air temperature was ±0.55 m w.e., whereas a ±10 % increase in precipitation represented a change of ± 0.20 m w.e. Model results further indicated that for a 2°C warming, the ablation season will be extended by c. 30 days and that the period of ice melt at the AWS location will increase from c. 40 to c. 80 days.

Halocarbon and pigment profiles in the waters of the Amundsen and Ross Seas, Antarctica

Little is known regarding the distribution of volatile halogenated organic compounds (halocarbons) in Antarctic waters, and their relation to biophysical variables. During the austral summer (December to January) in 2007-08 halocarbon and pigment concentrations were measured in the Amundsen (100-130ºW) and Ross Sea (158ºW- 160ºE). In addition, halocarbons were determined in air, snow and sea ice. The distribution of halocarbons was influenced to a large extent by sea ice, and to a much lesser extent by pelagic biota. Concentrations of naturally produced halocarbons were elevated in the surface mixed layer in ice covered areas compared to open waters in polynyas and in the bottom waters of the Ross Sea. Higher concentrations of halocarbons were also found in sea ice brine compared to the surface waters. Incubations of snow revealed an additional source of halocarbons. The distribution of halocarbons also varied considerably between the Amundsen and Ross Seas, mainly due to the different oceanographic settings. For iodinated compounds, weak correlations were found with the presence of pigments indicative of Phaeocystis, mainly in the Ross Sea. Saturation anomalies for the surface water and brine (in sea ice) were determined for the two indicator halocarbons bromoform and chloriodomethane. For bromoform, the surface water anomalies varied between -83 and 11%, whereas chloroiodomethane anomalies varied between -6 and 1,200%. The saturation anomalies for brine varied between -56 to 120% for bromoform and 91 to 22,000% for chloroiodomethane, indicating that sea ice could be a possible source both to the atmosphere and the surface waters. Polar waters can have a substantial impact on global halocarbon budgets and need to be included in large-scale assessments.