Allochthonous inputs

Marce R, Moreno-Ostos E, Lopez P, Armengol J (2008) The role of allochthonous inputs of dissolved organic carbon on the hypolimnetic oxygen content of reservoirs. Ecosystems 11 1035-1053... 

Variation among Sampling Sites. Dissolved humic substance samples from seven end-member environments were isolated for study. Autochthonous inputs to DOM were expected to dominate in Big Soda Lake and in Island Lake, which is a groundwater-sustained eutrophic lake in the sandhills of western Nebraska. Allochthonous inputs to DOM from a swamp environment predominate in the Suwannee River. They also dominate in the Calcasieu River in western Louisiana, but the proportion of swampland is much lower there. The Temi River is a tropical blackwater tributary of the Orinoco River in Venezuela, where allochthonous inputs dominate. The entire Sagavanirktok River basin is located north of the tree line on the North Slope of Alaska a mixture of allochthonous and autochthonous inputs was expected for the various rivers and lakes in this basin. Lastly, Hidden Lake Creek, which is the outlet of Hidden Lake on the Kenai Peninsula of Alaska, was sampled to determine if nutrient inputs from decaying salmon were contributing to primary production and autochthonous inputs to DOM. 

The Sagavanirktok River is intermediate in aromatic carbon content. This river drains the bogs on the Arctic tundra (allochthonous inputs) and several lakes (autochthonous inputs). Samples from the Suwannee and Calcasieu rivers are very similar in peak-height ratios with the exception of peak 2 1 ratio, which is much lower for the Calcasieu River sample. The data in Table II indicate that the Calcasieu River fulvic acid has a greater ring content... 

The major objective of this chapter is to examine and synthesize the published literature with respect to sources and production of terrestrially derived DOC, its relationship with dissolved organic nitrogen (DON), and the mechanistic controls on their export from terrestrial ecosystems to surface waters. With the exception of wet precipitation (which is ranked by continental landmass), we have classified data for throughfall and soil solution under biome type. Where possible, we have shown mean and standard deviations of some biomes to illustrate the amount of variance within and between biomes. Relationships between DOC and DON are illustrated using only those studies that report both DOC and DON concentration. Because most research on DOC and DON has been accomplished in relatively undisturbed areas, particularly forests, this chapter concentrates on the aspect of diffuse-source allochthonous inputs to surface waters and not point-source inputs from urban and agricultural areas. Recent work by Westerhoff and Anning (2000), however, indicates that more research on effluent or point-source DOC as a contributor to riverine allochthonous inputs may be... 

The dominant allochthonous inputs are from riverine, marine/estuarine plankton, and bordering terrestrial wetland sources. Autochthonous sources typically include plankton, benthic and epiphytic micro- and macroalgae, emergent and submergent (e.g., seagrasses) aquatic vegetation (EAV and SAV) within the estuary proper, and secondary production. 

Figure 10.12 Modeled controls on the heterotrophic organic nitrogen (HON) and percentage of HON based on the ratio of respired allochthonous inputs (Alloc. Resp.) in different aquatic systems. AON, allochthonous organic nitrogen AP, allochthonous production. (Modified from Caraco and Cole, 2003.)...

Allochthonous inputs from the Amazon River and local drainage thus contribute 4.3 Tg yr of organic carbon to floodplain. This represents approximately 4% of total plant production within the floodplain. However, the majority of the allochthonous inputs are refractory carbon, while most of the aquatic plant production is available to other trophic levels. 

Humic substances in lakes result from autochthonous biological processes within the lake and from allochthonous inputs from terrestrial sources. The macromolecular biological debris produced by biological wastewater treatment plants can have chemical and physical characteristics similar to natural organic... 

In conclusion, autochthonous humification processes in lakes must occur. The ratio of autochthonous to allochthonous input varies, of course, from lake to lake and depends on factors such as the specific ratio of watershed size to lake area, watershed structure, hydrologic input into the lake, productivity within a lake, and the relative sizes of pelagic and littoral zones of a lake. 

Lake Plussee (Muenster, in preparation) is a eutrophic hardwater lake of the Plon lake district. During the summer, concentrations of dissolved combined phenolic compounds oscillate drastically over short periods of time (as shown in Fig. 17 for epilimnetic waters), although DOC concentrations (measured as COD in glucose-carbon equivalents) were much more stable. Fluctuations in combined phenolic compounds correlate poorly with phytoplankton standing crop (Fig. 17, lowermost panel). Thus, distribution patterns of free phenols and phenolic compounds may result primarily from abiotic factors (e.g., photolysis, allochthonous inputs by rainstorms, or adsorption onto autochthonous calcite) or biotic ones other than release by phytoplankton (e.g., biodegradation after photolysis). These processes, which have not yet been quantified, obviously influence the upper water layers most, since absolute concentrations of phenolic compounds (as well as oscillations within the concentrations) are significantly lower in the deeper-water layers. Perhaps many of the phenols in the deeper strata occur in a particulate state, adsorbed onto sedimentary matter. Alternatively, total phenolic concentrations are really lower in the deeper strata if true, the reasons remain obscure. 

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