Uptake of Allochthonous Dissolved Organic Matter from Soil and Salmon in Coastal Temperate Rainforest Streams |
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Authors: | Jason B Fellman Eran Hood Richard T Edwards Jeremy B Jones |
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Institution: | (1) Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska 99775, USA;(2) Environmental Science Program, University of Alaska Southeast, Juneau, Alaska 99801, USA;(3) U.S.D.A. Forest Service, Pacific Northwest Research Station, Juneau, Alaska 99801, USA |
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Abstract: | Dissolved organic matter (DOM) is an important component of aquatic food webs. We compare the uptake kinetics for NH4–N and different fractions of DOM during soil and salmon leachate additions by evaluating the uptake of organic forms of carbon
(DOC) and nitrogen (DON), and proteinaceous DOM, as measured by parallel factor (PARAFAC) modeling of DOM fluorescence. Seasonal
DOM slug additions were conducted in three headwater streams draining a bog, forested wetland, and upland forest using DOM
collected by leaching watershed soils. We also used DOM collected from bog soil and salmon carcasses to perform additions
in the upland forest stream. DOC uptake velocity ranged from 0.010 to 0.063 mm s−1 and DON uptake velocity ranged from 0.015 to 0.086 mm s−1, which provides evidence for the whole-stream uptake of allochthonous DOM. These findings imply that wetlands could potentially
be an important source of DOM to support stream heterotrophic production. There was no significant difference in the uptake
of DOC and DON across the soil leachate additions (P > 0.05), although differential uptake of DOM fractions was observed as protein-like fluorescence was removed from the water
column more efficiently than bulk DOC and DON (P < 0.05). Moreover, PARAFAC analysis of DOM fluorescence showed that protein-like fluorescence decreased downstream during
all DOM additions, whereas humic-like fluorescence did not change. This differential processing in added DOM suggests slow
and fast turnover pools exist for aquatic DOM. Taken together, our findings argue that DON could potentially fill a larger
role in satisfying biotic N demand in oligotrophic headwater streams than previously thought.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
Author contributions J.B.F. conceived of or designed study, performed research, analyzed data, contributed new methods or models, and wrote the
paper. E.H. conceived of or designed study and analyzed data. R.T.E. conceived of or designed study and analyzed data. J.B.J.
contributed new methods or models and analyzed data. |
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Keywords: | DOM DOC DON Fluorescence PARAFAC salmon Wetlands Nutrient uptake |
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