TY - JOUR

T1 - Microbial use of low molecular weight DOM in filtered and unfiltered freshwater

T2 - Role of ultra-small microorganisms and implications for water quality monitoring

AU - Brailsford, Francesca

AU - Glanville, Helen

AU - Marshall, Miles

AU - Golyshin, Peter

AU - Jones, P.J.

AU - Yates, C.A.

AU - Owen, A.T.

AU - Jones, David L.

N1 - This work was carried out under the DOMAINE project, which is funded by the UK Natural Environment Research Council (NERC) (large grant NE/K010689/1).

PY - 2017/11/15

Y1 - 2017/11/15

N2 - 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.

AB - 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.

KW - Biodegration

KW - Metabolomics

KW - Sampling method

KW - Nutrients

KW - Ultramicrobacteria

KW - Uptake kinetics

U2 - 10.1016/j.scitotenv.2017.04.049

DO - 10.1016/j.scitotenv.2017.04.049

M3 - Article

VL - 598

SP - 377

EP - 384

JO - Science of the Total Environment

JF - Science of the Total Environment

SN - 0048-9697

ER -