title: Floating ice-algal aggregates below melting arctic sea ice.
abstract: During two consecutive cruises to the Eastern Central Arctic in late summer 2012, we observed floating algal aggregates in the melt-water layer below and between melting ice floes of first-year pack ice. The macroscopic (1-15 cm in diameter) aggregates had a mucous consistency and were dominated by typical ice-associated pennate diatoms embedded within the mucous matrix. Aggregates maintained buoyancy and accumulated just above a strong pycnocline that separated meltwater and seawater layers. We were able, for the first time, to obtain quantitative abundance and biomass estimates of these aggregates. Although their biomass and production on a square metre basis was small compared to ice-algal blooms, the floating ice-algal aggregates supported high levels of biological activity on the scale of the individual aggregate. In addition they constituted a food source for the ice-associated fauna as revealed by pigments indicative of zooplankton grazing, high abundance of naked ciliates, and ice amphipods associated with them. During the Arctic melt season, these floating aggregates likely play an important ecological role in an otherwise impoverished near-surface sea ice environment. Our findings provide important observations and measurements of a unique aggregate-based habitat during the 2012 record sea ice minimum year.
authors.affiliation: Norwegian Polar Institute, Fram Centre, Tromsø, Norway.
authors.forename: Philipp
authors.initials: P
authors.lastname: Assmy
authors.forename: Jens K
authors.initials: JK
authors.lastname: Ehn
authors.forename: Mar
authors.initials: M
authors.lastname: Fernández-Méndez
authors.forename: Haakon
authors.initials: H
authors.lastname: Hop
authors.forename: Christian
authors.initials: C
authors.lastname: Katlein
authors.forename: Arild
authors.initials: A
authors.lastname: Sundfjord
authors.forename: Katrin
authors.initials: K
authors.lastname: Bluhm
authors.forename: Malin
authors.initials: M
authors.lastname: Daase
authors.forename: Anja
authors.initials: A
authors.lastname: Engel
authors.forename: Agneta
authors.initials: A
authors.lastname: Fransson
authors.forename: Mats A
authors.initials: MA
authors.lastname: Granskog
authors.forename: Stephen R
authors.initials: SR
authors.lastname: Hudson
authors.forename: Svein
authors.initials: S
authors.lastname: Kristiansen
authors.forename: Marcel
authors.initials: M
authors.lastname: Nicolaus
authors.forename: Ilka
authors.initials: I
authors.lastname: Peeken
authors.forename: Angelika H H
authors.initials: AH
authors.lastname: Renner
authors.forename: Gunnar
authors.initials: G
authors.lastname: Spreen
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Tatarek
authors.forename: Jozef
authors.initials: J
authors.lastname: Wiktor
mesh_terms: D001110:Arctic Regions; D000458:Cyanobacteria; D017753:Ecosystem; D005615:Freezing; D005843:Geography; D007053:Ice; D046448:Ice Cover / Q000382:microbiology*; D012623:Seawater / Q000382:microbiology*
chemical_list: D007053:Ice