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Microbial heterotrophic utilization of dissolved organic matter in a piedmont stream

350 210 Stroud Water Research Center

Kaplan, L.A., and T.L. Bott. 1983. Freshwater Biology 13:363–377.

doi: 10.1111/j.1365-2427.1983.tb00686.x

Summary

  1. The microbial heterotrophic utilization of dissolved organic matter (DOM) was determined experimentally in microcosms using stream water and stream-bed sediments from a third order reach of White Clay Creek (Pennsylvania, U.S.A.).
  2. Sources of DOM for the experiments included White Clay Creek water at baseflow and stormflow and cold water extracts of jewel weed (Impatiens capensis L.) and spicebush (Lindera henzoin (L.) Blume).
  3. The heterotrophic activity of the sediments was measured as uptake of the following: dissolved organic carbon (DOC), molecular weight fractions within the DOC pool, carbohydrates, amino acids and peptides, phenolics, and dissolved oxygen (DO), all in the overlying water.
  4. Concentrations of adenosine triphosphate (ATP), and direct microscopic counts of bacteria were used to estimate bacterial biomass in the surface sediments.
  5. The microcosm experiments showed that specific DOC molecular size classes and DOM functional groups were selectively removed from solution, exposure to one DOM source affected responses to a different DOM source and certain DOM sources were more readily utilized than others.
  6. Continued exposure to a DOM source increased microbial heterotrophic activity (a condition which persisted even after removal of the DOM source for several days).
  7. Rates of biotic DOC uptake ranged from 3.6 to 242.8 mg Cm-2h-1.
  8. Indirect estimates of biosynthesis calculated from DOC and DO data ranged from 1.6 at baseflow and 2.6–61.2 at stormflow to as high as 192.6 mg C m-2 h-1 when the community was repeatedly exposed to enriched DOM sources.
  9. The mean generation times of bacteria in sediments, determined from direct microscopy data, ranged from 12.5 to 46.2 h at 15°C.

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