Ecosystem metabolism in a dryland river waterhole
C. S. Fellows A B , M. L. Wos A , P. C. Pollard A and S. E. Bunn AA Australian Rivers Institute, Griffith University, 170 Kessels Road, Nathan, Qld 4111, Australia.
B Corresponding author. Email: C.Fellows@griffith.edu.au
Marine and Freshwater Research 58(3) 250-262 https://doi.org/10.1071/MF06142
Submitted: 7 August 2006 Accepted: 7 December 2006 Published: 9 March 2007
Abstract
Little is known about ecosystem processes in dryland rivers, despite the global distribution of these systems. Those in Australia are characterised by long periods of no flow in which they persist for many months as series of isolated, often turbid, waterholes. We assessed benthic and pelagic primary production, respiration, and bacterial production in one of these waterholes to determine the metabolic balance of the waterhole and resolve the relative importance of autochthonous and allochthonous sources of organic carbon. Despite a photic zone depth of only 0.25 m, three lines of evidence suggested that autochthonous sources of organic carbon were important for fuelling bacterial production under no-flow conditions: the metabolic balance of the waterhole was not indicative of large allochthonous inputs; rates of gross primary production were great enough to meet a substantial fraction of estimated bacterial carbon demand; and pathways for allochthonous carbon to enter the waterhole were limited. These results suggest that models of lake metabolism based on temperate ecosystems can be expanded to include dryland river waterholes, which group with eutrophic lakes owing to their high levels of inorganic nutrients, low allochthonous inputs and autotrophic metabolic balance.
Additional keywords: gross primary production, heterotrophic bacteria, pelagic, respiration.
Acknowledgements
We would like to thank Eric Snyder, Stephen Balcombe, Courtney Henderson, Fran Sheldon, Wade Hadwen and two anonymous reviewers for their helpful comments on the manuscript. We are grateful to Joanne Clapcott for her contribution to the field work. This study was funded by the Cooperative Research Centre for Freshwater Ecology (project C200).
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