Microbial communities have evolved mechanisms to allow them to survive within the challenging and changing pack ice environment. One such mechanism may be the exudation of photosynthetically-derived organic carbon into various extracellular pools. During the 2nd Sea Ice Physics and Ecosystems eXperiment (SIPEX-2), East Antarctic pack ice productivity and subsequent carbon allocation were quantified, together with physico-biogeochemical characteristics (29 September–28 October, 2012). Mean ice thickness ranged between 0.80 and 2.16 m, and typically exhibited a warm ice interior with weak temperature gradients. All stations, with one exception, were layered with granular (mean: 78%), columnar (mean: 15%), and mixed granular/columnar (mean: 4%) ice. Highest ice brine-volume fractions were at the ice–water interface, but all ice had high brine-volume fractions conducive for brine percolation (mean: 15%). Dissolved inorganic nutrient concentrations in the brine were scattered around theoretical dilution lines (TDLs), with some values of nitrate and nitrite, ammonium and silicic acid falling below TDLs, indicating nutrient depletion. Bulk ice dissolved organic carbon was low (mean: 64 µmol kg⁻¹), but most samples showed enrichment in relation to TDLs. Microbial biomass (bacterial and algal) was low, and generally showed maxima in the sea-ice interior. Bottom ice algal communities were dominated by pennate diatom species (mean: 86% of total cell abundance). ¹⁴C-total primary productivity (¹⁴C-TPP) ranged from <0.01 to 2.22 mg C (mg chl a)⁻¹ d⁻¹ (<0.01 to 3.03 mg C m⁻² d⁻¹). The relative contribution of ¹⁴C-total extracellular organic carbon (¹⁴C-TEOC) to ¹⁴C-TPP decreased over the observational period (range: 44–21%), with the remaining proportion being ¹⁴C-particulate organic carbon. ¹⁴C-TEOC composition was dominated by low molecular weight ¹⁴C-extracellular dissolved organic carbon (mean: 61%), with the remaining proportion allocated to ¹⁴C-colloidal organic carbon. Production of ¹⁴C-extracellular polymeric substances was not detected at any station.

Item Type:	Refereed Article
Keywords:	sea ice, primary production, micro algae, extracellular polemic substance, EPS, biomass, carbon
Research Division:	Biological Sciences
Research Group:	Ecology
Research Field:	Marine and estuarine ecology (incl. marine ichthyology)
Objective Division:	Environmental Management
Objective Group:	Management of Antarctic and Southern Ocean environments
Objective Field:	Biodiversity in Antarctic and Southern Ocean environments
UTAS Author:	Ugalde, SC (Ms Sarah Ugalde)
UTAS Author:	McMinn, A (Professor Andrew McMinn)
UTAS Author:	Meiners, KM (Dr Klaus Meiners)
ID Code:	113146
Year Published:	2016
Web of Science® Times Cited:	17
Deposited By:	Ecology and Biodiversity
Deposited On:	2016-12-14
Last Modified:	2018-04-18
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