Title Arctic sea-ice ridges; safe heavens for sea-ice fauna during periods of extreme ice melt?
Author Gradinger, R.; Bluhm, B.A.; Iken, K.
Author Affil Gradinger, R., University of Alaska-Fairbanks, School of Fisheries and Ocean Sciences, Fainbanks, AK
Source Observations and exploration of the Arctic's Canada Basin and the Chukchi Sea; the hidden ocean and RUSALCA expeditions, edited by B.A. Bluhm, K. Iken and R.R. Hopcroft. Deep-Sea Research. Part II: Topical Studies in Oceanography, 57(1-2), p.86-95, . Publisher: Elsevier, Oxford, International. ISSN: 0967-0645
Publication Date Jan. 2010
Notes In English. 57 refs. GeoRef Acc. No: 310306
Index Terms algae; carbon isotopes; chlorophylls; ecology; ice; isotopes; melting; meltwater; plankton; plant ecology; pressure ridges; salinity; temperature; thickness; Arctic Ocean--Beaufort Sea; Arctic Ocean--Canada Basin; Arctic Ocean--Chukchi Sea; Arctic Ocean; Beaufort Sea; C-13/C-12; Canada Basin; carbon; chlorophyll; Chukchi Sea; fresh water; habitat; ice cores; Invertebrata; isotope ratios; N-15/N-14; nitrogen; organic carbon; organic compounds; organic nitrogen; pigments; Plantae; porphyrins; sea ice; sea water; spatial distribution; stable isotopes; zooplankton
Abstract The abundances and distribution of metazoan within-ice meiofauna (13 stations) and under-ice fauna (12 stations) were investigated in level sea ice and sea-ice ridges in the Chukchi/Beaufort Seas and Canada Basin in June/July 2005 using a combination of ice coring and SCUBA diving. Ice meiofauna abundance was estimated based on live counts in the bottom 30 cm of level sea ice based on triplicate ice core sampling at each location, and in individual ice chunks from ridges at four locations. Under- ice amphipods were counted in situ in replicate (N=24-65 per station) 0.25 m2 quadrats using SCUBA to a maximum water depth of 12 m. In level sea ice, the most abundant ice meiofauna groups were Turbellaria (46%), Nematoda (35%), and Harpacticoida (19%), with overall low abundances per station that ranged from 0.0 to 10.9 ind l-1 (median 0.8 ind l-1). In level ice, low ice algal pigment concentrations (0.1-15.8 g Chl a l-1), low brine salinities (1.8-21.7) and flushing from the melting sea ice likely explain the low ice meiofauna concentrations. Higher abundances of Turbellaria, Nematoda and Harpacticoida also were observed in pressure ridges (0-200 ind l-1, median 40 ind l-1), although values were highly variable and only medians of Turbellaria were significantly higher in ridge ice than in level ice. Median abundances of under-ice amphipods at all ice types (level ice, various ice ridge structures) ranged from 8 to 114 ind m-2 per station and mainly consisted of Apherusa glacialis (87%), Onisimus spp. (7%) and Gammarus wilkitzkii (6%). Highest amphipod abundances were observed in pressure ridges at depths 3 m where abundances were up to 42- fold higher compared with level ice. We propose that the summer ice melt impacted meiofauna and under-ice amphipod abundance and distribution through (a) flushing, and (b) enhanced salinity stress at thinner level sea ice (less than 3m thickness). We further suggest that pressure ridges, which extend into deeper, high-salinity water, become accumulation regions for ice meiofauna and under-ice amphipods in summer. Pressure ridges thus might be crucial for faunal survival during periods of enhanced summer ice melt. Previous estimates of Arctic sea ice meiofauna and under-ice amphipods on regional and pan-Arctic scales likely underestimate abundances at least in summer because they typically do not include pressure ridges.
URL http://hdl.handle.net/10.1016/j.dsr2.2009.08.008
Publication Type journal article
Record ID 65007257