Publication Date:
2019-07-17
Description:
Sea ice plays a dynamic role in the air‐sea exchange of CO2. In addition to abiotic
inorganic carbon fluxes, an active microbial community produces and remineralizes
organic carbon, which can accumulate in sea ice brines as dissolved organic matter
(DOM). In this study, the characteristics of DOM fluorescence in Antarctic sea ice brines
from the western Weddell Sea were investigated. Two humic‐like components were
identified, which were identical to those previously found to accumulate in the deep ocean
and represent refractory material. Three amino‐acid‐like signals were found, one of which
was unique to the brines and another that was spectrally very similar to tryptophan and
found both in seawater and in brine samples. The tryptophan‐like fluorescence in the
brines exhibited intensities higher than could be explained by conservative behavior during
the freezing of seawater. Its fluorescence was correlated with the accumulation of
nitrogen‐rich DOM to concentrations up to 900 mmol L−1 as dissolved organic carbon
(DOC) and, thus, potentially represented proteins released by ice organisms. A second,
nitrogen‐poor DOM fraction also accumulated in the brines to concentrations up to
200 mmol L−1 but was not correlated with any of the fluorescence signals identified.
Because of the high C:N ratio and lack of fluorescence, this material is thought to
represent extracellular polymeric substances, which consist primarily of polysaccharides.
The clear grouping of the DOM pool into either proteinaceous or carbohydrate‐dominated
material indicates that the production and accumulation of these two subpools of DOM in
sea ice brines is, to some extent, decoupled.
Repository Name:
EPIC Alfred Wegener Institut
Type:
Article
,
isiRev
Format:
application/pdf
Permalink
