Acclimation of stream-bed heterotrophic microflora: metabolic responses to dissolved organic matter |
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Authors: | LOUIS A KAPLAN THOMAS L BOTT |
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Institution: | Stroud Water Research Center, Academy of Natural Sciences of Philadelphi, Avondale, Pennsylvania, U.S.A. |
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Abstract: | SUMMARY. - 1 Studies were performed to assess the acclimation of the stream-bed heterotrophic microflora to sources of dissolved organic matter (DOM) typical of its environment and microfloral responses to pulses of DOM.
- 2 Microcosm measurements of dissolved organic carbon (DOC) uptake, dissolved oxygen uptake. ATP concentration and epitluorescence microscopic counts (EMC) were performed using stream-bed sediments and heterogeneous dissolved organic matter (DOM) sources.
- 3 Three study sites included an undisturbed woodlot spring seep, a small stream traversing a cattle pasture and a larger stream draining a catchment used for silage crops, pastures and woodlands.
- 4 The DOM sources were cold water extracts of forest floor leaf litter, bovine manure, the green alga Ulothrix and jewel weed (Impaliens capensis L.) leaves.
- 5 DOC uptake occurring in 2.5–5.0 h incubations indicated an acclimation of the microflora at each site to DOM sources generated by surrounding land use.
- 6 The sediment microflora from the larger stream did not readily metabolize bovine manure DOM and the latter was used in an acclimation experiment.
- 7 A minimum of 48 h of cumulative exposure to bovine manure DOM at 15–20°C were required to yield measurable changes in sediment microbial activity of sediment microbial biomass.
- 8 The same microflora retained an ability to readily metabolize the added DOM source after 72 h of exposure to unamended stream water.
- 9 The time frame of microfloral responses during acclimation indicated that changes leading to the metabolism of a DOM source were initially enzymatic and eventually involved growth and selection for specific decomposers within the microbial community.
- 10 We conclude that in order to utilize naturally occurring pulses of carbon and energy, stream-bed heterotrophs must be already enzymatically prepared, induced, when the pulse occurs.
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