Environmental and Water Quality Operational Studies: Size Distribution of Planktonic Autotrophy and Microheterotrophy in DeGray and West Point Reservoirs: A Comparative Study.
OAK RIDGE NATIONAL LAB TN ENVIRONMENTAL SCIENCES DIV
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Planktonic autotrophy in both reservoirs was dominated by microalgae, with usually 60 of the total photosynthetic carbon uptake associated with organisms in the 8.0-micrometer size fraction. Microheterotrophic activity in the 0.2- to 1.0-micrometer size fraction fraction indicative of small, free-living bacterioplankton rather than of large bacteria or bacteria attached to suspended particles usually accounted for 80 of the planktonic microheterotrophy. Relative to marked uplake-to-downlake gradients in physical and chemical conditions, size distributions of autotrophy and microheterotrophy were remarkably uniform in both reservoirs. Uplake-to-downlake shifts in size distributions appear to correspond to within-reservoir transitions from riverine to lacustrine conditions however, the specific environmental factors controlling the size distributions of planktonic autotrophy and microheterotrophy ramain uncertain. Our results suggest that additional ecological factors e.g., size-selective losses of cells by grazing andor sinking, autotroph-microheterotroph interactions must be considered, in addition to the availability of nutrients and suspended particles, as potential environment controls on the size distributions of planktonic autotrophy and microheterotrophy.
- Hydrology, Limnology and Potamology