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Photodegradation, interaction with iron oxides and bioavailability of dissolved organic matter from forested floodplain sources

journal contribution
posted on 2008-01-01, 00:00 authored by Julia Howitt, D Baldwin, G Rees, B Hart
Photochemical degradation of dissolved organic matter (DOM) can influence food webs by altering the availability of carbon to microbial communities, and may be particularly important following periods of high DOM input (e.g. flooding of forested floodplains). Iron oxides can facilitate these reactions, but their influence on subsequent organic products is poorly understood. Degradation experiments with billabong (= oxbow lake) water and river red gum (Eucalyptus camaldulensis) leaf leachate were conducted to assess the importance of these reactions in floodplain systems. Photochemical degradation of DOM in sunlight-irradiated quartz tubes (with and without amorphous iron oxide) was studied using gas chromatography and UV-visible spectroscopy. Photochemical reactions generated gaseous products and small organic acids. Bioavailability of billabong DOM increased following irradiation, whereas that of leaf leachate was not significantly altered. Fluorescence excitation-emission spectra suggested that the humic component of billabong organic matter was particularly susceptible to degradation, and the source of DOM influenced the changes observed. The addition of amorphous iron oxide increased rates of photochemical degradation of leachate and billabong DOM. The importance of photochemical reactions to aquatic systems will depend on the source of the DOM and its starting bioavailability, whereas inputs of freshly formed iron oxides will accelerate the processes.

History

Journal

Marine and freshwater research

Volume

59

Issue

9

Pagination

780 - 791

Publisher

CSIRO Publishing

Location

Collingwood, Vic.

ISSN

1323-1650

eISSN

1448-6059

Language

eng

Publication classification

C1 Refereed article in a scholarly journal

Copyright notice

2008, CSIRO

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