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Communication at the NABS Annual meeting, Keystone, 2000
(104) THE INFLUENCE OF HYDROLOGICAL SEASONALITY ON BACTERIAL PRODUCTION AND ABUNDANCE IN LOWLAND RIVERS OF THE ORINOCO BASIN, VENEZUELA.
M.M. Castillo. School of Natural Resources and Environment, The University of Michigan, Ann Arbor, MI 48109-1115
I examined temporal changes in bacterial production and abundance in relatively undisturbed lowland rivers of the middle Orinoco basin by sampling two clearwater and two blackwater rivers over two years. Bacterial numbers increased during the period of rising water and declined during the periods of low and high water, likely as a result of allochthonous bacterial inputs into the rivers. Bacterial production peaks were observed during the periods of low (blackwater rivers), rising (clearwater rivers) or falling water (all rivers). These trends were associated with higher chlorophyll concentrations during low water in blackwater rivers and with increasing DOC concentrations during rising water, due to flushing of organic material from surrounding land areas. The period of high water was accompanied by low bacterial production levels at all river sites, and may be related to DOC quality and low abundance of active bacteria. Higher seasonal variation was observed in DOC, bacterial production, and abundance during the first year of study, due to higher seasonal differences in discharge in the first compared to the second year of study. Seasonal and interannual changes in discharge appear to affect availability of substrate and activity of the bacterial assemblage, resulting in temporal variation in bacterial production.
Presented at 10:45 AM on Tuesday, May 30, 2000 in Food Webs and Communities II
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