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Microbial uptake kinetics of dissolved organic carbon (DOC) compound groups from river water and sediments

Research output: Contribution to journalArticle

Original languageEnglish
Article number11229
Pages (from-to)1-11
Number of pages11
JournalScientific Reports
Volume9
Early online date2 Aug 2019
DOIs
DateE-pub ahead of print - 2 Aug 2019
DatePublished (current) - 2 Aug 2019

Abstract

Dissolved organic matter (DOM) represents a key component of carbon (C) cycling in freshwater ecosystems. While the behaviour of bulk dissolved organic carbon (DOC) in aquatic ecosystems is well studied, comparatively little is known about the turnover of specifc DOC compounds. The aim of this study was to investigate the persistence of 14C-labelled low molecular weight (LMW) DOC at a wide range of concentrations (0.1µM to 10mM), in sediments and waters from oligotrophic and mesotrophic rivers within the same catchment. Overall, rates of DOC loss varied between compound groups (amino acids>sugars=organic acids>phenolics). Sediment-based microbial communities contributed to higher DOC loss from river waters, which was attributed, in part, to its greater microbial biomass. At higher DOC compound concentrations, DOC loss was greater in mesotrophic rivers in comparison to oligotrophic headwaters. A lag-phase in substrate use within sediments provided evidence of microbial growth and adaptation, ascribed here to the lack of inorganic nutrient limitation on microbial C processing in mesotrophic communities. We conclude that the higher microbial biomass and available inorganic nutrients in sediments enables the rapid processing of LMW DOC, particularly during high C enrichment events and in N and P-rich mesotrophic environments.

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