Please use this identifier to cite or link to this item:
Title: Size distribution of planktonic autotrophy and microheterotrophy in DeGray and West Point Reservoirs : a comparative study
Authors: Oak Ridge National Laboratory. Environmental Sciences Division.
Environmental and Water Quality Operational Studies (U.S.)
Kimmel, Bruce L.
Groeger, Alan W.
Keywords: Freshwater plankton
DeGray Lake
West Point Lake
Heterotrophic bacteria
Publisher: Environmental Laboratory (U.S.)
Engineer Research and Development Center (U.S.)
Description: Technical Report
Abstract: Particle size is an important determinant of food resources available to planktonic consumers and of the efficiency of energy transfer through planktonic foodwebs. Thus, the environmental factors controlling the size distributions of planktonic autotrophy (algal photosynthesis) and microheterotrophy (bacterial heterotrophic activity) are of considerable ecological interest. To examine hypotheses regarding their environmental control, the authors compared the size distributions of planktonic autotrophy and microheterotrophy within and between oligotrophic DeGray Reservoir (Arkansas) and eutrophic West Point Reservoir (Alabama-Georgia). Naturally occurring assemblages of reservoir phytoplankton and bacterioplankton were radiolabeled with sodium 14C -bicarbonate and sodium 3H-acetate and were size-fractionated by filtration through polycarbonate membrane filters. 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-μm size fraction. Microheterotrophic activity in the 0.2- to 1.0-μm size 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 remain uncertain. Our results suggest that additional ecological factors (e.g., size-selective losses of cells by grazing and/or sinking, autotroph-microheterotroph interactions) must be considered, in addition to the availablility of nutrients and suspended particles, as potential environmental controls on the size distributions of planktonic autotrophy and microheterotrophy.
Rights: Approved for public release; distribution is unlimited.
Appears in Collections:Technical Report

Files in This Item:
File Description SizeFormat 
TR-E-86-8.pdf8.49 MBAdobe PDFThumbnail