Size distribution of autotrophy and microheterotrophy in reservoirs: implications for foodweb structure
Particle size is a primary determinant of resources available to consumers and of the efficiency of energy transfer through planktonic food chains. Dual radioisotopic labeling (with /sup 14/C-bicarbonate and /sup 3/H-acetate) and size fractionation of naturally-occurring phytoplankton-bacterioplankton assemblages were employed to examine the particle size distributions of planktonic autotrophy and microheterotrophy in four limnologically-dissimilar US reservoirs (Lake Mead, Arizona-Nevada, oligo-mesotrophic; Broken Bow Lake, Oklahoma, mesotrophic; Lake Texoma, Oklahoma-Texas, eutrophic; and Normandy Lake, Tennessee, eutrophic). Small nano- and ultraphytoplankton (< 8.0 ..mu..m) and free-living bacteria (< 3.0 ..mu..m) were primarly responsible for planktonic autotrophy and microheterotrophy, respecitvely, even in eutrophic conditions. Zooplankton grazing experiments indicated that (1) most grazing pressure occurs on 3.0 to 8.0 ..mu..m particles, (2) grazer limitation of the occurrence of attached bacteria amd microbial-detrital aggregates is unlikely, and (3) free-living bacteria are inefficiently harvested, relative to algae, by most reservoir zooplankton. Relative to autorophy, the microheterotrophic conversion of allochthonous dissolved organic matter and algal excretion products to bacterial biomass appears unlikely to be a significant source of organic carbon for planktonic grazers in most reservoirs.
- Research Organization:
- Oak Ridge National Lab., TN (USA)
- DOE Contract Number:
- W-7405-ENG-26
- OSTI ID:
- 5179124
- Report Number(s):
- CONF-8106240-1; ON: DE82017531
- Country of Publication:
- United States
- Language:
- English
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54 ENVIRONMENTAL SCIENCES
ALGAE
AQUATIC ECOSYSTEMS
BACTERIA
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CARBON 14
CARBON ISOTOPES
ECOSYSTEMS
ENERGY TRANSFER
EVEN-EVEN NUCLEI
FOOD CHAINS
HYDROGEN ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
LIGHT NUCLEI
MICROORGANISMS
NUCLEI
NUTRIENTS
ODD-EVEN NUCLEI
ORGANIC MATTER
PARTICLE SIZE
PLANTS
PRODUCTIVITY
RADIOISOTOPES
SIZE
SURFACE WATERS
TRACER TECHNIQUES
TRITIUM
WATER RESERVOIRS
YEARS LIVING RADIOISOTOPES