Rocker , Dagmar and Kisand, Veljo and Scholz-Böttcher, Barbara and Kneib, Thomas and Lemke, Andreas and Rullkötter, Jürgen and Simon, Meinhard (2012) Differential decomposition of humic acids by marine and estuarine bacterial communities at varying salinities. Biogeochemistry, 111. pp. 331-346. ISSN 0168-2563

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Humic substances (HS) constitute 50–80% of total dissolved organic matter (DOM) in freshwaters but in the open ocean\3%, indicating that large fractions of DOM and HS are removed in the estuarine and coastal zone. In order to assess the role of bacteria in this removal, we conducted experiments in flowthrough cultures to examine the decomposition of peat bog-born humic acids (HA) by marine (salinity 30, Exp1) and estuarine (salinity 10, Exp2) bacterial communities. After *70 days 40–[60% of the HA were decomposed. Highest fractions were decomposed in treatments in which the bacterial communities were fed by HA media of a foreign salinity, e.g., of 14 in Exp1 and of 28 in Exp2. Some of the HA material was not decomposed but broken down to smaller moieties entering the fulvic acid (FA) fraction. The analysis of the HA media and their residuals after bacterial decomposition by pyrolysis GC/MS showed that individual organic compounds were decomposed. In Exp1, 32 aliphatic and aromatic compounds, including lignin biomarkers, were detected in the HA medium of which mainly aliphatic compounds were decomposed. In Exp2, 49 compounds were detected of which *40–60% were not detected any more after bacterial decomposition in the HA fraction but still in the FA fraction. The results show that estuarine and marine bacterial communities can decompose large amounts of HA and that this process is important in reducing the amount of terrestrial HS and DOM entering the estuarine and coastal region.

Item Type: Article
Uncontrolled Keywords: Humic matter, DOC, Bacteria, Flowthrough culture, Pyrolysis-GC/MS
Subjects: Science and mathematics
Science and mathematics > Chemistry
Science and mathematics > Earth sciences and geology
Science and mathematics > Life sciences, biology
Science and mathematics > Plants (botany)
Divisions: Faculty of Mathematics and Science > Institute for Chemistry and Biology of the Marine Environment (ICBM)
Date Deposited: 28 Feb 2014 11:44
Last Modified: 28 Feb 2014 11:44
URN: urn:nbn:de:gbv:715-oops-18767
DOI: 10.1007/s10533-011-9653-4

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