Seabird density and predation on Arctic cod (Boreogadus saida) in Allen Bay in 2010

Seabirds feed heavily on Arctic cod Boreogadus saida during the summer in the Canadian Arctic but little is known of the interactions among birds while foraging and the factors that drive feeding behaviour. The objective of this study was to describe the relationship between seabirds and Arctic cod in a productive feeding area distant from breeding colonies. Transect surveys were completed using standardized count protocols to determine the density of seabirds in Allen Bay, Cornwallis Island, Nunavut. Shore-based observation sites determined seabird foraging behaviour associated with the presence of schools and environmental variables. The density of birds (156 bird/km**2) was high compared to that of other locations in the Canadian Arctic. Several bird species were more active early in the morning and with winds from the south, possibly due to an increase in Arctic cod feeding on zooplankton at the surface. Northern fulmars Fulmarus glacialis and black-legged kittiwakes Rissa tridactyla captured Arctic cod directly from the water; however, they lost nearly 25% of captures to glaucous gulls Larus hyperboreus and parasitic jaegers Stercorarius parasiticus. These kleptoparasitic seabirds benefited the most in Allen Bay obtaining as much as 8 times more Arctic cod than species capturing cod directly. Northern fulmars captured 3 times more Arctic cod from schools, and black-legged kittiwakes captured similar proportions of schooling and non-schooling cod. We conclude that non-schooling Arctic cod are as important as schooling cod as an energy source for seabirds in nearshore areas, such as Allen Bay, during the summer.

Investigation of Bacteria in coastal waters of King George Island

We determined the numbers of free-living and associated (aggregated or bonded with particles) bacteria in the coastal water of King George Island at an offshore (St. 1) and a nearshore station (St. 2) as a function of physico-chemical parameters. Water sampIes were collected between March and October at St. 1 and between April and October at St. 2. Direct counts of total bacteria varied from 0.53*10**8 to 5.02*10**8 cells/l. Associated microorganisms accounted for 5 to 20 % of the total number of bacteria. Strong Spearman and Pearson correlations were observed (R = 0.82; P = 0.001) between the numbers of free-living and associated bacteria at St. 1. These two groups of bacteria were nearly evenly distributed in the horizontal transects from inshore to offshore waters at depths of 1-10 m in Ardley Cove. There were no substantial differences in the numbers of either free-living or associated bacteria in vertical transects too. Their number at St. 1, but not at St. 2, correlated significantly with all tested environmental parameters (salinity, temperature, solar radiation, nitrate, phosphate and chlorophyll a concentrations), except nitrite concentrations in water. The most probable reason for these correlations is that a common seasonal trend is characteristic of most tested parameters during the March to October period.

(Table 1) Egg size, clutch asymmetry, hatch date and breeding success in south polar skua, brown skua and mixed pairs on King George Island

We studied how environmental conditions affect reproduction in sympatric skua species that differ in their reliance on marine resources: the exclusively marine foraging south polar skua Catharacta maccormicki, the terrestrially foraging brown skua C. antarctica lonnbergi and mixed species pairs with an intermediate diet. Egg size, clutch asymmetry and hatching dates varied between species and years without consistent patterns. In the south polar skuas, 12 to 38% of the variation in these parameters was explained by sea surface temperature, sea ice cover and local weather. In mixed species pairs and brown skuas, the influence of environmental factors on variation in clutch asymmetry and hatching date decreased to 10-29%, and no effect on egg size was found. Annual variation in offspring growth performance also differed between species with variable growth in chicks of south polar skuas and mixed species pairs, and almost uniform growth in brown skuas. Additionally, the dependency on oceanographic and climatic factors, especially local wind conditions, decreased from south polar skuas to brown skua chicks. Consistent in all species, offspring were more sensitive to environmental conditions during early stages; during the late chick stage (>33 d) chick growth was almost independent of environmental conditions. The net breeding success could not be predicted by any environmental factor in any skua species, suggesting it may not be a sensitive indicator of environmental conditions. Hence, the sensitivity of skuas to environmental conditions varied between species, with south polar skuas being more sensitive than brown skuas, and between breeding periods, with the egg parameters being more susceptible to oceanographic conditions. However, during offspring development, local climatic conditions became more important. We conclude that future climate change in the Maritime Antarctic will affect reproduction of skuas more strongly through changes in sea ice cover and sea surface temperature (and the resulting alterations to the marine food web) than through local weather conditions.

14 ground-penetrating radar lines of Area 5 - Periglacial outwash plain from Potter Cove, King George Island, Antarctic Peninsula

During a field campaign in the Austral spring 2012 the sedimentary architecture of a periglacial flood plain at the northeastern coast of Potter Peninsula (Area 5) was revealed using ground-penetrating radar (GPR, Geophysical Survey Systems, Inc. SIR-3000). 14 profiles were collected using a mono-static 200 MHz antenna operated in common offset mode. Trace increment was set to 0.05 m. A differential global-positioning system (dGPS, Leica GS09) was used to obtain topographical information along the GPR lines. GPR data are provided in RADAN-Format, dGPS coordinates are provided in ascii format; projection is UTM (WGS 84, zone 21S).