Distribution, abundance, and predation effects of epipelagic ctenophores and jellyfish in the western Arctic Ocean Jennifer E. Purcell a,Ã , Russell R. Hopcroft b , Ksenia N. Kosobokova c , Terry E. Whitledge b a Western Washington University, Shannon Point Marine Center,1900 Shannon Point Rd, Anacortes, WA 98221, USA b Institute of Marine Science, University of Alaska Fairbanks, Fairbanks, AK 99775-7220, USA c Shirshov Institute of Oceanology RAS, 36 Nakimova Avenue,117997 Moscow, Russian Federation article info Available online 13 August 2009 Keywords: Gelatinous zooplankton ROV Competition Climate change abstract The Arctic Ocean is undergoing changes at an unprecedented rate because of global climate change. Especially poorly-studied in arctic waters are the gelatinous zooplankton, which are difficult to study using traditional oceanographic methods. A distinct zooplanktivore community was characterized in the surface 100 m by use of a Remotely Operated Vehicle, net collections, and SCUBA diving. The large scyphomedusa, Chrysaora melanaster , was associated with the warm Pacific water at 35–75 m depth. A diverse ctenophore community lived mainly above the C. melanaster layer, including Dryodora glandula, a specialized predator of larvaceans, Beroe cucumis, a predator of other ctenophores, and the extremely fragile Bolinopsis infundibulum, which was the most abundant species. Gut content analyses showed that Mertensia ovum selectively consumed the largest copepods (Calanus spp.) and amphipods (Parathemisto libellula); B. infundibulum consumed smaller copepods and pteropods (Limacina helicina). Large copepods were digested by M. ovum in 12 h at 1.5 to 0 1C, but by B. infundibulum in only 4 h. We estimated that M. ovum consumed an average of 2% d 1 of the Calanus spp. copepods and that B. infundibulum consumed 4% d 1 of copepods o3 mm prosome length. These are significant consumption rates given that Calanus spp. have life-cycles of 2 or more years and are eaten by vertebrates including bowhead whales and arctic cod. & 2009 Elsevier Ltd. All rights reserved. 1. Introduction Little is known about the ctenophores, siphonophores, hydro- medusae, and scyphomedusae in polar seas (Pag  es, 1997). Basic descriptions of gelatinous zooplankton from the Arctic Ocean are widely scattered in the published literature over the past century (e.g., Bigelow, 1920; Stepanjants, 1989; Sirenko, 2001), but these generally provide only information on their occurrence, without information on their abundance or ecology. One of the few exceptions shows gelatinous species to be relatively abundant throughout the water column (Raskoff et al., 2005). The above gelatinous taxa are predators, whose feeding on zooplankton, such as the abundant copepods (Smith and Schnack- Schiel, 1990; Conover and Huntley, 1991; Mumm et al., 1998; Hopcroft et al., 2005), generally is of unknown importance in the Arctic. Only a few studies consider the trophic importance of carnivorous gelatinous species in Arctic surface waters. In the eastern Arctic, the ctenophore, Mertensia ovum, is a predominant gelatinous species year-round (Percy, 1989; Swanberg and B˚ amstedt, 1991a, b; Siferd and Conover, 1992; Lundberg et al., 2006). These ctenophores were estimated to consume up to 9% d 1 of the populations of the larger copepods (Calanus glacialis) and 3–4% d 1 of the smaller copepod species (Siferd and Conover, 1992). Other under-studied gelatinous predators may have similar ecological importance (e.g., Hosia and B ˚ amstedt, 2007). Bolinopsis spp. ctenophores are widely distributed but little-studied because of their fragile construction (exceptions are Kremer et al., 1986; Kasuya et al., 1994; Kinoshita et al., 2006). They are reported from boreal waters (Siferd and Conover, 1992; Raskoff et al., 2005; Hosia and B ˚ amstedt, 2007), but their importance as predators is unknown. The Arctic Ocean has strong near-surface discontinuities of temperature and salinity and deeper distinct water masses of different origin layered throughout the water column. The main layers include a thin, low-salinity layer immediately below the ice (o10m depth), then a mixed layer (o40 m) followed by a layer originating from the Bering Strait and West-Wind Ridge (40– 200 m), the Atlantic waters entering the Arctic through Fram Strait (350–600 m), and waters of uniquely Arctic character below 600m (McLaughlin et al., 2005). The vertical distributions of gelatinous zooplankton are known to be related to the physical structure in the water column. Numerous examples exist of ARTICLE IN PRESS Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/dsr2 Deep-Sea Research II 0967-0645/$ - see front matter & 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.dsr2.2009.08.011 Ã Corresponding author. Fax: +1360 293 1083. E-mail address: purcelj3@wwu.edu (J.E. Purcell). Deep-Sea Research II 57 (2010) 127–135