Dissolved organic matter in Antarctic sea ice

Abstract

ABSTRACT. It has been hypothesized that there are significant dissolved organic matter (DOM) pools in sea-ice systems, although measurements of DOM in sea ice have only rarely been made. The significance of DOM for ice-based productivity and carbon turnover therefore remains highly speculative. DOM within sea ice from the Amundsen and Bellingshausen Seas, Antarctica, in 1994 and theWeddell Sea, Antarctica, in 1992 and 1997 was investigated. Measurements were made on melted sea-ice sections in 1994 and 1997 and in sea-ice brines in 1992. Dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) concentrations in melted ice cores were up to 1.8 and 0.78 mM, respectively, or 30 and 8 times higher than those in surface water concentrations, respectively. However, when concentrations within the brine channel/pore space were calculated from estimated brine volumes, actual concentrations of DOC in brines were up to 23.3 mM and DON up to 2.2 mM, although mean values were 1.8 and 0.15 mM, respectively. There were higher concentrations of DOM in warm, porous summer second-year sea ice compared with colder autumn first-year ice, consistent with the different biological activity supported within the various ice types. However, in general there was poor correlation between DOC and DON with algal biomass and numbers of bacteria within the ice. The mean DOC/DON ratio was 11, although again values were highly variable, ranging from 3 to highly carbon-enriched samples of 95. Measurements made on a limited dataset showed that carbohydrates constitute on average 35% of the DOC pool, with highly variable contributions of 1^99%.

Role of sea ice in global biogeochemical cycles: emerging views and challenges

“…Columnar ice growth at the ice base [Notz and Worster, 2009] and snow ice formation associated with surface flooding trap salt [Maksym and Jeffries, 2000;Vancoppenolle et al, 2010], as well as dissolved and particulate material [Krembs et al, 2001;Giannelli et al, 2001] initially present in seawater, promoting the development of bottom and surface ice algal communities. Rising frazil ice crystals are known to harvest some of the available particulate material suspended in the water column and to incorporate it in the ice [Martin, 1981;Garrison et al, 1983;Ackley and Sullivan, 1994].…”

“…DOC concentrations of up to > 2.5 x 10 3 µM have been reported for Arctic sea ice [Riedel et al, 2008]. DOC concentrations in Antarctic sea ice vary widely with values of up to >1.8 x 10 3 µM in melted ice cores [e.g., Thomas et al, 2001;Herborg et al, 2001;. As DOC is further concentrated within sea ice brines, organisms living in brine are exposed to DOC concentrations that are up to 3 orders of magnitude higher than in seawater.…”

Exopolymer alteration of physical properties of sea ice and implications for ice habitability and biogeochemistry in a warmer Arctic

“…Earlier, we suggested that the presence of EPS, which dominate (9, 15) the millimolar amounts of organic carbon measured in sea ice (16), may modify pore space or interfere with salt expulsion from growing ice, leading to higher ice porosities and salinities (9,10). Here, we have tested this hypothesis via detailed microscopic observations of the brine inclusions in well-characterized coastal sea ice (Barrow, AK) near the growing ice front and in laboratory ice grown from saline solutions with and without added EPS, coupled with measurements of salt retention.…”

Strategies for the Simulation of Sea Ice Organic Chemistry: Arctic Tests and Development

“…During real world succession, more complex relationships are naturally observed [16,60]. Furthermore, the full complement of biomacromolecules necessarily includes mixed functionality polymers that are organic combinations of the idealized compound classes represented here [7][8]17,27].…”

“…Injected, chained carbon can subsequently be degraded to oligomeric or even monomeric subunits [7,27,60]. Recondensation and hetero-polymerization then come into play [27].…”