Kaplan L.A.

biogeochemistry of dissolved organic carbon entering streams

Kaplan, L. A., and J. D. Newbold, Biogeochemistry of dissolved organic
carbon entering streams, in Aquatic Microbiology: An Ecological Approach,
edited by T. E. Ford, pp. 139 – 165, Blackwell Sci., Malden,
Mass., 1993.

Patterns of Dissolved Organic Carbon in Transport

Patterns of Dissolved Organic Carbon in Transport
Louis A. Kaplan, Richard A. Larson and Thomas L. Bott
Limnology and Oceanography
Vol. 25, No. 6 (Nov., 1980), pp. 1034-1043

Abstract: 
Two distinct patterns of dissolved organic carbon (DOC) in transport were observed in a southeastern Pennsylvania piedmont drainage basin under low flow conditions. In relatively undisturbed woodland spring seeps, DOC concentrations increased with distance from the groundwater sources as did the apparent percentage of high molecular weight DOC. Changes in pH, color, and phenolic-C paralleled those for total DOC in a seep, while the concentration of carbohydrate-C remained relatively constant. In headwater areas perturbed by humans, cattle, or waterfowl, elevated DOC concentrations decreased rapidly from point source inputs.

Diel Fluctuations of DOC Generated by Algae in a Piedmont Stream

Diel Fluctuations of DOC Generated by Algae in a Piedmont Stream
Louis A. Kaplan and Thomas L. Bott
Limnology and Oceanography
Vol. 27, No. 6 (Nov., 1982), pp. 1091-1100

Abstract: 
Diel fluctuations in dissolved organic carbon (DOC) were measured in White Clay Creek, a piedmont stream in SE Pennsylvania. DOC concentrations, measured on 16 days from late March to early June and on 2 days in early November, 1978 and 1979, showed rapid increases from predawn minima to late afternoon maxima and gradual decreases after sunset. Concentrations increased during a single day by as much as 40% of the daily minimum. These measurements were made during periods of constant discharge and were not related to volume of flow or changes in groundwater DOC concentrations. Laboratory and microcosm experiments suggested that benthic algae excreted most of the DOM and that bacterial uptake modified its concentration and composition. When the diel pulse was strongest, net algal DOC excretion accounted for 20% of the total DOC exported from the watershed that day. Additional data show that the 14C method of measuring algal excretion is quantitatively and qualitatively inaccurate for periphyton incubated for 2-4 h.
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