Autochthonous processes

In contrast to rivers and lakes, autochthonous processes appear to be the overwhelmingly dominant source of DOC in the oceans. In a survey of shallow and deep waters of the Atlantic and Pacific Oceans, Opsahl and Benner (1997) used concentrations of lignin in DOM to determine that terrigenous matter accounted for only 0.7-2.4% of the DOC present. Terrigenous DOC concentrations were about 2.6 times higher in the Atlantic than in the Pacific Ocean, presumably because of the 3.6 times greater riverine water discharge to the Atlantic. 

The experimental aspects of this study were focussed on two hard-water lakes in Switzerland, namely, the northern basin of Lake Zurich and Lake Sempach. The hydraulic residence time of Lake Zurich is 1.2 years. Most of the particles in the lake are produced directly or indirectly by biological processes within the lake itself (e.g., photosynthesis, CaC03 precipitation). Phosphorus removal has been implemented in recent years at all wastewater treatment plants discharging into the lake at present Lake Zurich can be described as between meso- and eutrophic. Lake Sempach has an average hydraulic residence time of 15.8 years as in Lake Zurich, particles in the lake waters are primarily autochthonous. Phosphorus concentrations have increased substantially and the lake is eutrophic. 

Most of the organic matter in seawater was created in situ by marine processes and is, hence, classified as autochthonous. Organic matter of nonmarine origin is classified as allochthonous and is primarily terrestrial detritus, transported by rivers or winds. The input of organic matter from rivers is small (0.4 Pg C/y) compared to primary productivity (40 to 50 Pg C/y). The aeolian input is unknown but thought to be significant. 

Functional processes are essentially the same in both freshwater and marine systems, the differences become apparent when the emphasis is placed on the source of the organic matter (OM). The source of this OM affects the rate at which it is used not the overall process of use (Wetzel, 2000). These rates differ because of the greater influx of humic or recalcitrant materials in inland systems versus the dominating inputs of autochthonous OM in marine systems. These studies show that bacterial populations do respond to differences in the DOM pool. The challenge now lies in increasing the scope of these studies to find patterns in the spatiotemporal distribution... 

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... 

As mentioned, Tokuzen223 examined local, cellular reactions around Sarcoma 180 grafts during the process of regression under polysaccharide treatment, and found a massive outpouring of lymphoid cells one week after tumor implantation. Autochthonous grafts of spontaneous, mammary tumors, not at all inhibited by polysaccharides, called forth no local, lymphoid-cell infiltration.252... 

The division into laterite and ferricrete used in this chapter represents a useful process-based distinction, but the practicality of determining whether mineral components of a profile are allochthonous or autochthonous is problematic because many lateritic weathering profiles are subsequently modified by the introduction of allochthonous materials. Conversely, once formed, ferricretes can be subject to weathering processes in situ and evolve toward more lateritic-type profiles. Nevertheless, the distinction between dominantly autochthonous weathering profiles or allochthonous alteration profiles is an important one because it places constraints upon the processes operating during duricrust evolution, and also upon contemporaneous climatic and geomorphological conditions. 

In principle, this figure is valid for both lakes and running water. In clear lakes, the input of carbon via autochthonous production (and the humification process per se) is of greater significance than in rivers and bogs where allochthonous humic material predominates. 

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. 

Allochthonous vs. autochthonous organic matter - key UV-VIS mediated processes regulate heterotrophic utilization... 

Phytoplankton abundance responds to nutrients, light, and grazing pressure. The primary autochthonous source of CDOM is often assumed to be photosynthetic organisms, but heterotrophic bacteria may play an important role by processing the relatively UV-transparent photosynthate and releasing modified compounds that absorb UVR more strongly [91]. Spatial and temporal linkage between CDOM and the microbial community appears complex and difficult to... 

Biodegradation Biodegradation of hydrocarbons by natural populations of microorganisms (such as many species of bacteria, fungi, and yeasts) represents one of the primary mechanisms by which petroleum and other hydrocarbon pollutants are eliminated from the environment. The biodegradation of petroleum and other hydrocarbons in the environment is a long-term complex process, whose quantitative and qualitative aspects depend on the type, nature and amount of the oil or hydrocarbon present, the ambient and seasonal environmental conditions (such as temperature, oxygen, nutrients, water activity, sahnity, and pH), and the composition of the autochthonous microbial community. 

The overall distribution pattern of sediment types in the world s oceans depends on few elementary factors. The most important factor is the relative amount with which one particle species contributes to sediment formation. Particle preservation and eventual dilution with other sediment components will modify the basic pattern. The formation and dispersal of terrigenous constituents derived from weathering processes on the continents, as well as autochthonous oceanic-biogenic constituents, both strongly depend on the prevalent climate conditions, so that, in the oceans, a latitude-dependent and climate-related global pattern of sediment distribution will be the ultimate result. 

---