Carbon detritus

Fig. 2.5 Timeseries of daily phytoplankton, zooplankton, dissolved organic carbon, detritus, and phosphorus concentration, and photosyntesis over one model year at two location the shelf seas of the Pacific Ocean, 170 E 65 N and 140 E 10 S.

Limestone (chiefly calcite, CaCOa) and dolomite rocks (chiefly dolomite, CaMg(C03)2) are exposed at about 20% of Earth s surface. Carbonate detritus, fossil shell materials, and carbonate cements are also common in noncarbonate sedimentary rocks and arid-climate soils. The carbonate minerals found in such occurrences, in decreasing order of importance, are calcite, dolomite, magnesian cal-cites (Cai jMgfCOa where jc is usually <0.2), aragonite (a CaCOa polymorph) and, perhaps, magnesite. As a rule of thumb, when such materials are present in silicate or aluminosilicate rocks or soils at a level of about 1 % or more, they will lend to dominate the chemistry of the soil or ground-water. This fact is extremely important when one is concerned about the ability of a rock to neutralize acid mine waters, other acid wastewaters, or acid rain. 

Reservoir rocks are either of clastic or carbonate composition. The former are composed of silicates, usually sandstone, the latter of biogenetically derived detritus, such as coral or shell fragments. There are some important differences between the two rock types which affect the quality of the reservoir and its interaction with fluids which flow through them. 

Outer crust. A friable outer crust forms atop the tubercle. The crust is composed of ferric hydroxide (hematite), carbonates, silicates, other precipitates, settled particulate, and detritus. Ferrous ion and ferrous hydroxide generated within the tubercle diffuse outward through fis-... 

Tubercles consisted of hard, hlack oxide shells overlaid with friable carbonate-containing deposits. In places, several laminate black magnetite shells existed. The outer crust could be crushed by gentle pressure with a finger. Tubercles were riddled with white crystalline fibers. Other detritus was incorporated into the tubercle core and crust. Metal loss was less than 0.030 in. (0.076 cm) below each tubercle. Wall thickness was almost 0.25 in. (0.64 cm). 

The turnover time of carbon in biota in the ocean surface water is 3 x 10 /(4 + 36) x lO yr 1 month. The turnover time with respect to settling of detritus to deeper layers is considerably longer 9 months. Faster removal processes in this case must determine the turnover time respiration and decomposition. 

Fig. 11-12 Detrital carbon dynamics for the 0-20 cm layer of chernozem grassland soil. Carbon pools (kg C/ m ) and annual transfers (kg C/m per year) are indicated. Total profile content down to 20 cm is 10.4 kg C/m. (Reproduced with permission from W. H. Schlesinger (1977). Carbon balance in terrestrial detritus, Ann. Rev. Ecol. Syst. 8,51-81, Annual Reviews, Inc.)...

Schlesinger, W. H. (1977). Carbon balance in terrestrial detritus. Ann. Ecol. Syst. 8, 51-81. 

Since phosphorus is not oxidized diuang the respiration of organic matter, it does not contribute to the O2 uptake. Thus, 138 mol O2 is consumed diuang the respiration of 1 mol of average plankton detritus, making the molar ratio of organic carbon respired to O2 consumed equal to 106 138. 

The object of the present study was to measure the ratios of organic carbon, nitrogen, and hydrogen in the detritus sinking in lake water and in the sediments and to discuss the decomposition processes of these components in order to gain basic knowledge concerning the mechanism of coal formation. 

Ratios of Organic Carbon and Nitrogen in Settling Detritus. The ratios of Org. C/Org. N of plankton, sediments collected at 25 meters in water, and surface bottom sediments in Lake Kizaki-ko are 5.7, 9.3, and 15.5, respectively (Table I). 

In order to clarify the mechanism of microbiological decomposition of organic carbon and nitrogen of detritus in the lake water, the gaseous and nitrogenous components as well as the other chemical characteristics were determined in Lake Kizaki-ko, September 7-8, 1963 and October 28-31, 1963 when stagnation had greatly advanced in the lake. 

The fact that the average ratio of Miner. C/Miner. N (2.83) is considerably smaller than the ratio of Org. C/Org. N of plankton (5.7) indicates clearly that the organic nitrogen in plankton is more easily mineralized than the organic carbon by microbiological activities and also that the mineralization processes are active in the lake water. This fact may account for the relationship between the ratios of Org. C/Org. N of plankton, of detritus and of surface bottom sediments, which has been shown previously. 

For the most part, sediments are also stratigraphically uniform, showing only a few percentage variation in lithologic composition. Cores from Mountain Lake, which consistently show up-core decreases in carbonate content (to about 60% that at depth), are the only exception. A number of shallow-water cores that contain a thin veneer of organic-rich sediments overlying silt and sand were also excluded from analysis. In most locations the spatial boundary between organic-rich profundal-type sediments and littoral deposits of coarse detritus or massive silt was clearly defined. 

Analyses of carbon isotopic composition were performed as an independent measure of potential food sources for zooplankton. The 813C values of terrestrial detritus and of littoral zone emergents such as Carex ranged from -26.0 to -29.2%o (Table I 49, 92). By comparison, the zooplankton were quite depleted in 13C their 813C values were more similar to phytoplankton and ranged from -32.1%o in Daphnia to -41.0%o in Cyclops (Table I). 

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