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.

Chemical composition of bottom sediments from the northern part of the Deryugin Trough, Sea of Okhotsk

Distribution trace element contents in the upper (up to 5 m) Holocene-Upper Pleistocene sediment layer along the northern and southern sublatitudinal profiles in the northern part of the Deryugin Trough is discussed. Mathematical processing of chemical analysis data has been made. On the basis of the cluster analysis 16 elements have been combined into 5 geochemical groups. Two of them (1 - Ag-Mo group and 2 - Mn-Ba-Ni-Sr group) were considered in detail. Analysis of Ag and Mo distributions in the sediments and findings of molybdenite permitted to conclude that enrichment of the sediments by these elements resulted from edaphic washing of magmatic rocks containing Ag-Mo mineralization and probably located on the northwestern slope of the Deryugin trough. The second geochemical group is most likely connected with hydrothermal barite mineralization found in the northeastern part of the Deryugin trough. Considering Mn distribution in bottom sediment cores supply of Mn was pulsating. This allows concluding that during Holocene - Late Pleistocene three cycles of hydrothermal activity occurred in the Deryugin Trough, and the most intensive one was in Holocene.