Allochthonous carbon

In this chapter, we develop a simple model that predicts the maximum possible heterotrophic organic N formation as a function of the importance of allochthonous carbon inputs. We then review data from the literature on the relative importance of heterotrophic organic N formation in aquatic systems. This material is presented in a landscape context, following a flow path of organic matter from streams to the open ocean. We consider a variety of evidence to look at heterotrophic organic N formation, including enhancement of decomposition by N additions and ecosystem budgets. We rely, however, primarily on data from 15N addition studies to quantify the... 

The maximum value of HON/AON increases in systems with allochthonous carbon inputs. The maximum potential is related directly to the allochthonous organic matter input that is respired in the system (Alloch. Resp.). Additionally, the increased HON will depend on the relative growth efficiency of heterotrophic bacteria on allochthonous material (BGEa och) and the C N ratio of allochthonous material (C Nalloc]l), such that... 

Allochthonous carbon loads to rivers are generally greater than this average primary production. Inputs generally appear to vary between 300 and 3000 g C m 2yr 1 and may average close to 1000 g C m 2yr 1 (Richey et al., 1990 Findlay et al., 1997 Caraco and Cole, 1999, 2002). Not all of... 

Caraco, N. F., and J. J. Cole. 2002. When terrestrial carbon is sent down the river Importance of allochthonous carbon inputs to the metabolism of lakes and rivers. In Food Webs at the Landscape Level (G. A. Polis and M. E. Power, Eds.). University of Chicago Press. 

In Scheme 3, the alkalinity concentration is plotted against pH from Lake Horkkajarvi, in southern Finland (61°13 N, 25°10 E). Lake Horkkajarvi is a truly meromictic lake where water column mixing periods, due to homothermal conditions, are absent [26]. hi northern temperate zones, lakes usually circulate twice a year, i.e. in spring and fall, but in a meromictic lake permanent stratification separates the lake into two layers. The stabilising forces in Lake Horkkajarvi are high electrolyte concentration and the sheltered position of the landscape. The lake is 1.1 ha in area with a maximum and mean depth of 13 and 7 m, respectively. It is a humic lake greatly affected by the allochthonous carbon load the water colour in units of mg Pt 11 is >200. 

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... 

The geology of Cyprus is dominated by four distinct terranes - the Troodos Ophiolite Complex composed of mafic and ultramafic rocks, the Circum-Troodos Sedimentary Sequence containing calcarenites, siltstones and carbonates, the Mamonia Complex composed of igneous, sedimentary and metamorphic rocks and the Kyrenia Terrain containing a series of allochthonous massive and recrystallised limestones dolomites and marbles. These terranes generate highly varied landscapes (Fig 1). 

Figure 1. Allochthonous and autochthonous sources of dissolved organic carbon in natural waters. (Reproduced with permission from reference 1. Copyright 1985 Kluwer Academic Publishers.)...

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... 

III. Regulation of Allochthonous Dissolved Organic Carbon and Dissolved Organic Nitrogen 51... 

III. REGULATION OF ALLOCHTHONOUS DISSOLVED ORGANIC CARBON AND DISSOLVED ORGANIC NITROGEN... 

McCart, E., A. M. Gordon, N. K. Kaushik, B. Lazerte, E. Mallory, R. W. Bachmann, J. R. Jones, R. H. Peters, and D. M. Soballe. 1995. Characterization of selected allochthonous organic carbon inputs within a terrestrial-aquatic ecotone in Algonquin Park, Ontario. Lake Reserve Management 11 168. 

Stable carbon isotope ratios have also been used to determine the sources of lake DOC. Baron et al. (1991) used 13C analysis to show that autochthonous sources dominated the DOC of an alpine lake during most periods while allochthonous sources dominated the DOC in a subalpine lake. The high DOC concentrations observed during spring snowmelt and early summer in both lakes, however, were mostly derived from allochthonous sources. As with streams and rivers, synoptic regional studies of 13C and 14C would provide important new information on broad spatial patterns and controls on the sources of DOC in lakes. 

Rounick, J. S., M. J. Winterbourn, and G. L. Lyon. 1982. Differential utilization of allochthonous and autochthonous inputs by aquatic invertebrates in some New Zealand streams A stable carbon isotope study. Oikos 39 191—198. 

Jansson, M., A. K. Bergstrom, P. Blomqvist, A. Isaksson, and A. Jonsson. 1999. Impact of allochthonous organic carbon on microbial food web carbon dynamics and structure in Lake Ortrasket. Archive fur Hydrobiologia 144 409—428. 

Aside from adding defined compounds, experimental additions of natural DOM mixtures suspected to vary in lability have helped test ideas about the contribution of various DOM sources to aquatic ecosystems. In a nice example using manipulation of natural DOM sources, Battin et al. (1999) used flowthrough microcosms to measure the relative uptake rates of allochthonous and autochthonous DOM by stream sediments. They documented greater than fivefold differences or more in uptake and respiration, depending on whether the DOM was extracted from soil or periphyton. Moreover, they were able to show, via transplant experiments, several cases where prior exposure to a particular source of DOM increased the ability of that community to metabolize the DOM supplied. There appears to be some preadaptation of microbial catabolic capacity when these stream biofilms were re-exposed to a familiar type of DOM. Similarly, the response of heterotrophic bacteria to carbon or nutrient addition was greatest when the source community was particularly active (Foreman et al., 1998). Kaplan et al. (1996) showed that fixed film bioreactors, colonized on one water source, were unable to rapidly metabolize DOC in water from another source. 

The formula for BCD in Eq. (2) was derived under the assumption that the bacterial growth rate was mineral nutrient limited. If the supply rate of labile organic carbon from allochthonous and autochthonous sources is insufficient to meet this demand, the pool of labile dissolved organic carbon (DOC) will eventually be depleted and the bacteria will become carbon... 

The DOC/enzyme/microbe interaction (DEMI) model divides bacterioplankton into two functional guilds, opportunists and decomposers, and DOC into two pools, labile and recalcitrant. In the context of the model, labile DOC is defined as directly assimilable monomers (saccharides, amino acids, and organic acids) and readily hydrolyzed polymers (polysaccharides, proteins, and nucleic acids). Because these substrates turn over rapidly, thus are unlikely to be transported far, most of the carbon in this pool will be autochthonous lysates and exudates, or allochthonous leachates from storms or seasonal litter fall. Recalcitrant DOC is defined as humic substances created by oxidative reactions among proteins, polysaccharides, hydrocarbons, and phenolic molecules. For inland waters, recalcitrant DOC is largely of allochthonous origin. 

Wetzel, R. G., and A. Otsuki. 1974. Allochthonous organic carbon of a marl lake. Archiv fiir Hydrobiologie 73 31-56. 

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