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Microbial use of low molecular weight DOM in filtered and unfiltered freshwater: Role of ultra-small organisms and implications for water quality monitoring

Marshall

Microbial use of low molecular weight DOM in filtered and unfiltered freshwater: Role of ultra-small organisms and implications for water quality monitoring Thumbnail


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Abstract

Dissolved organic matter (DOM) plays a central role in regulating productivity and nutrient cycling in freshwaters. It is therefore vital that we can representatively sample and preserve DOM in freshwaters for subsequent analysis. Here we investigated the effect of filtration, temperature (5 and 25 °C) and acidification (HCl) on the persistence of low molecular weight (MW) dissolved organic carbon (DOC), nitrogen (DON) and orthophosphate in oligotrophic and eutrophic freshwater environments. Our results showed the rapid loss of isotopically-labelled glucose and amino acids from both filtered (0.22 and 0.45 µm) and unfiltered waters. We ascribe this substrate depletion in filtered samples to the activity of ultra-small (< 0.45 µm) microorganisms (bacteria and archaea) present in the water. As expected, the rate of C, N and P loss was much greater at higher temperatures and was repressed by the addition of HCl. Based on our results and an evaluation of the protocols used in recently published studies, we conclude that current techniques used to sample water for low MW DOM characterisation are frequently inadequate and lack proper validation. In contrast to the high degree of analytical precision and rigorous statistical analysis of most studies, we argue that insufficient consideration is still given to the presence of ultra-small microorganisms and potential changes that can occur in the low MW fraction of DOM prior to analysis.

Acceptance Date Apr 7, 2017
Publication Date Apr 25, 2017
Publicly Available Date Mar 28, 2024
Journal Science of the Total Environment
Print ISSN 0048-9697
Publisher Elsevier
Pages 377-384
DOI https://doi.org/10.1016/j.scitotenv.2017.04.049
Keywords Biodegradation; Metabolomics; Sampling Method; Nutrients; Ultramicrobacteria; Uptake kinetics
Publisher URL http://www.sciencedirect.com/science/article/pii/S0048969717308847

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