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This paper compares and contrasts the ecosystems of the Barents and Chukchi Seas. Despite their similarity in a number of features, the Barents Sea supports a vast biomass of commercially important fish, but the Chukchi does not. Here we examine a number of aspects of these two seas to ascertain how they are similar and how they differ. We then indentify processes and mechanisms that may be responsible for their similarities and differences.Both the Barents and Chukchi Seas are high latitude, seasonally ice covered, Arctic shelf-seas. Both have strongly advective regimes, and receive water from the south. Water entering the Barents comes from the deep, ice-free and "warm" Norwegian Sea, and contains not only heat, but also a rich supply of zooplankton that supports larval fish in spring. In contrast, Bering Sea water entering the Chukchi in spring and early summer is cold. In spring, this Bering Sea water is depleted of large, lipid-rich zooplankton, thus likely resulting in a relatively low availability of zooplankton for fish. Although primary production on average is similar in the two seas, fish biomass density is an order of magnitude greater in the Barents than in the Chukchi Sea. The Barents Sea supports immense fisheries, whereas the Chukchi Sea does not. The density of cetaceans in the Barents Sea is about double that in the Chukchi Sea, as is the density of nesting seabirds, whereas, the density of pinnipeds in the Chukchi is about double that in the Barents Sea. In the Chukchi Sea, export of carbon to the benthos and benthic biomass may be greater. We hypothesize that the difference in fish abundance in the two seas is driven by differences in the heat and plankton advected into them, and the amount of primary production consumed in the upper water column. However, we suggest that the critical difference between the Chukchi and Barents Seas is the pre-cooled water entering the Chukchi Sea from the south. This cold water, and the winter mixing of the Chukchi Sea as it becomes ice covered, result in water temperatures below the physiological limits of the commercially valuable fish that thrive in the southeastern Bering Sea. If climate change warms the Barents Sea, thereby increasing the open water area via reducing ice cover, productivity at most trophic levels is likely to increase. In the Chukchi, warming should also reduce sea ice cover, permitting a longer production season. However, the shallow northern Bering and Chukchi Seas are expected to continue to be ice-covered in winter, so water there will continue to be cold in winter and spring, and is likely to continue to be a barrier to the movement of temperate fish into the Chukchi Sea. Thus, it is unlikely that large populations of boreal fish species will become established in this Arctic marginal sea. © 2012 Elsevier B.V.

The spread of invasive species in riparian forests has the potential to affect both terrestrial and aquatic organisms linked through cross-ecosystem resource subsidies. However, this potential had not been explored in regards to terrestrial prey subsidies for stream fishes. To address this, we examined the effects of an invasive riparian tree, European bird cherry (EBC, Prunus padus), spreading along urban Alaskan salmon streams, by collecting terrestrial invertebrates present on the foliage of riparian trees, their subsidies to streams, and their consumption by juvenile coho salmon (Oncorhynchus kisutch). Riparian EBC supported four to six times less terrestrial invertebrate biomass on its foliage and contributed two to three times lower subsidies relative to native deciduous trees. This reduction in terrestrial invertebrate biomass was consistent between two watersheds over 2 years. In spite of this reduction in terrestrial prey resource input, juvenile coho salmon consumed similar levels of terrestrial invertebrates in stream reaches bordered by EBC. Although we did not see ecological effects extending to stream salmonids, reduced terrestrial prey subsidies to streams are likely to have negative consequences as EBC continues to spread. La propagation d'especes envahissantes dans les forets ripisylves a le potentiel d'influencer les organismes terrestres et aquatiques relics par l'entremise d'apports de ressources entre ccosystemes. Ce potentiel n'a toutefois pas ctc explorce en ce qui concerne les apports de proies terrestres pour les poissons de cours d'eau. Nous avons donc examinc les effets de la propagation d'un arbre riverain envahissant, le cerisier a grappes d'Europe (Prunus padus, CGE), le long de rivieres a saumons en Alaska en caractcrisant les invertcbrcs terrestres prcsents dans le feuillage d'arbres riverains, leurs apports aux cours d'eau et la consommation qu'en font les saumons cohos (Oncorhynchus kisutch) juvcniles. Les CGE riverains a soutenu une biomasse d'invertcbrcs terrestres sur leur feuillage de quatre a six fois infcrieure et a contribuc des apports de deux a trois fois infcrieurs a ceux d'arbres feuillus indigenes. Une telle reduction de la biomasse d'invertcbrcs terrestres a ctc observce dans deux bassins versants et sur deux annces. Malgrc cette rcduction des apports de ressources de proies terrestres, les saumons cohos juvcniles consommaient des quantitcs semblables d'invertcbrcs dans les troncons de cours d'eau bordcs par des CGE. Bien qu'aucun effet ccologique n'ait ctc observc sur les salmonidcs lotiques, il est probable que la reduction des apports de proies terrestres dans les cours d'eau aura des conscquences ncgatives a mesure qu'avance la propagation des CGE. [Traduit par la Rcdaction], Introduction Stream and riparian ecosystems are linked through resource subsidies that extend beyond ecosystem boundaries, supporting adjacent species and food webs (Polis et al. 1997; Nakano and Murakami 2001; Power [...]