INVERTEBRATE AND FISH ASSEMBLAGE RELATIONS TO DISSOLVED OXYGEN MINIMA IN LOWLAND STREAMS OF SOUTHWESTERN LOUISIANA
Article first published online: 12 NOV 2012
Copyright © 2012 John Wiley & Sons, Ltd.
River Research and Applications
Volume 30, Issue 1, pages 11–28, January 2014
How to Cite
Justus, B. G., Mize, S. V., Wallace, J. and Kroes, D. (2014), INVERTEBRATE AND FISH ASSEMBLAGE RELATIONS TO DISSOLVED OXYGEN MINIMA IN LOWLAND STREAMS OF SOUTHWESTERN LOUISIANA. River Res. Applic., 30: 11–28. doi: 10.1002/rra.2623
- Issue published online: 6 JAN 2014
- Article first published online: 12 NOV 2012
- Manuscript Accepted: 15 OCT 2012
- Manuscript Revised: 26 SEP 2012
- Manuscript Received: 16 MAY 2012
- dissolved oxygen;
- threshold response;
- intermediate disturbance;
- lowland streams;
Dissolved oxygen (DO) concentrations in lowland streams are naturally lower than those in upland streams; however, in some regions where monitoring data are lacking, DO criteria originally established for upland streams have been applied to lowland streams. This study investigated the DO concentrations at which fish and invertebrate assemblages at 35 sites located on lowland streams in southwestern Louisiana began to demonstrate biological thresholds.
Average threshold values for taxa richness, diversity and abundance metrics were 2.6 and 2.3 mg/L for the invertebrate and fish assemblages, respectively. These thresholds are approximately twice the DO concentration that some native fish species are capable of tolerating and are comparable with DO criteria that have been recently applied to some coastal streams in Louisiana and Texas. DO minima >2.5 mg/L were favoured for all but extremely tolerant taxa. Extremely tolerant taxa had respiratory adaptations that gave them a competitive advantage, and their success when DO minima were <2 mg/L could be related more to reductions in competition or predation than to DO concentration directly.
DO generally had an inverse relation to the amount of agriculture in the buffer area; however, DO concentrations at sites with both low and high amounts of agriculture (including three least-disturbed sites) declined to <2.5 mg/L. Thus, although DO fell below a concentration that was identified as an approximate biological threshold, sources of this condition were sometimes natural (allochthonous material) and had little relation to anthropogenic activity. Copyright © 2012 John Wiley & Sons, Ltd.