Bioavailability of dissolved organic carbon and fulvic acid from an Australian floodplain river and billabong
Suzanne McDonald A , Jennifer M. Pringle B , Paul D. Prenzler A , Andrea G. Bishop A and Kevin Robards A CA School of Science and Technology, Charles Sturt University, Wagga Wagga, NSW 2678, Australia.
B Department of Materials Engineering, Monash University, Wellington Road, Clayton, VIC 3800, Australia.
C Corresponding author. Email: krobards@csu.edu.au
Marine and Freshwater Research 58(2) 222-231 https://doi.org/10.1071/MF06085
Submitted: 17 May 2006 Accepted: 3 November 2006 Published: 16 February 2007
Abstract
Dissolved organic carbon (DOC) is a vital resource for heterotrophic bacteria in aquatic ecosystems. The bioavailability of fulvic acid, which comprises the majority of aquatic DOC, is not well understood. The present study examined the bioavailability of bulk DOC and fulvic acid from two contrasting but inter-related water bodies: the Murrumbidgee River and adjacent Berry Jerry Lagoon. Bacteria utilised fulvic acids; however, bulk DOC was more bioavailable. Bacteria were able to utilise Murrumbidgee River DOC and fulvic acid more readily than Berry Jerry Lagoon DOC and fulvic acid, suggesting that the quality of carbon may be an important factor to consider when evaluating lateral exchange of nutrients between the main channel and floodplain. Chemical characteristics of fulvic acids appeared to explain some of the variation in fulvic acid bioavailability. The higher the molecular weight and complexity of the fulvic acid, the longer it took for bacteria to utilise the substrate (lag phase), but the larger the number of bacteria that grew on the substrate. The present study calls attention to the need for further multidisciplinary studies to address the quality of carbon in riverine-floodplain ecosystems.
Additional keywords: aquatic ecosystem, bacteria, DOC, energy flow, humic substances.
Acknowledgements
The authors wish to thank Prof. Barry Hart for his comments on the manuscript and Simon McDonald (SPAN, Charles Sturt University) for his help with statistical analysis. We would also like to thank the Department of Materials Engineering at Monash University for the use of their NMR instrument, and funding from an ARC Discovery Grant (DP0452937) that made the analyses possible. Charles Sturt University is thanked for financial assistance, and an APA scholarship to S. McDonald is gratefully acknowledged. We also thank the reviewers of the manuscript for their helpful comments.
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