Carbon biota

Parameter SEDIMENT ((Xg/kg dry weight normalised to 2.5 % carbon) BIOTA - blue mussel ( ig/kg dry weight) BIOTA - fish ( Ig/kg wet weight)... 

Bjorkstrom, A. 1979. A model of CO2 interaction between atmosphere,oceans, and land biota. In The Global Carbon Cycle, Bolin, B. Degens, E. T. Kempe, S. Ketner, P., Eds. SCOPE 13 J Wiley Sons New York, NY, 1979 pp 403-457. 

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. 

In situations where Tobs is comparable in magnitude to tq, a more complex relation prevails between Q, S, and M. Atmospheric CO2 falls in this last category although its turnover time (3 years, cf. Fig. 4-3) is much shorter than Tobs (about 300 years). This is because the atmospheric CO2 reservoir is closely coupled to the carbon reservoir in the biota and in the surface layer of the oceans (Section 4.3). The effective turnover time of the combined system is actually several hundred years (Rodhe and Bjdrk-strom, 1979). 

The cycles of carbon and the other main plant nutrients are coupled in a fundamental way by the involvement of these elements in photosynthetic assimilation and plant growth. Redfield (1934) and several others have shown that there are approximately constant proportions of C, N, S, and P in marine plankton and land plants ("Redfield ratios") see Chapter 10. This implies that the exchange flux of one of these elements between the biota reservoir and the atmosphere - or ocean - must be strongly influenced by the flux of the others. 

Large amounts of carbon are found in the terrestrial ecosystems and there is a rapid exchange of carbon between the atmosphere, terrestrial biota, and soils. The complexity of the terrestrial ecosystems makes any description of their role in the carbon cycle a crude simplification and we shall only review some of the most important aspects of organic carbon on land. Inventories of the total biomass of terrestrial ecosystems have been made by several researchers, a survey of these is given by Ajtay etal.(1979). 

Primary production maintains the main carbon flux from the atmosphere to the biota. In the process of photosynthesis, CO2 from the atmosphere is reduced by autotrophic organisms to a wide range of organic substances. The complex biochemistry involved can be represented by the formula... 

The exchange of CO2 between the atmosphere and terrestrial biota is one of the prime links in the global carbon cycle. This is seen by studying the variations of C in the atmosphere. Figure 11-14 presents atmospheric A C for the years... 

The subsequent fate of the assimilated carbon depends on which biomass constituent the atom enters. Leaves, twigs, and the like enter litterfall, and decompose and recycle the carbon to the atmosphere within a few years, whereas carbon in stemwood has a turnover time counted in decades. In a steady-state ecosystem the net primary production is balanced by the total heterotrophic respiration plus other outputs. Non-respiratory outputs to be considered are fires and transport of organic material to the oceans. Fires mobilize about 5 Pg C/yr (Baes et ai, 1976 Crutzen and Andreae, 1990), most of which is converted to CO2. Since bacterial het-erotrophs are unable to oxidize elemental carbon, the production rate of pyroligneous graphite, a product of incomplete combustion (like forest fires), is an interesting quantity to assess. The inability of the biota to degrade elemental carbon puts carbon into a reservoir that is effectively isolated from the atmosphere and oceans. Seiler and Crutzen (1980) estimate the production rate of graphite to be 1 Pg C/yr. 

Fig. 11 -25 Release of carbon from the biota and soils globally according to various estimates. The fossil fuel flux is from data of Rotty. (Modified with permission from G. M. Woodwell et al. (1983). Global deforestation Contribution to atmospheric carbon dioxide. Science 222,1081-1086, AAAS.)...

Bjdrkstrom, A. (1979). A model of CO2 interaction between atmosphere, oceans, and land biota. In "The Global Carbon Cycle" (B. Bolin, E. T. Degens, S. Kempe, and P. Ketner, eds), pp. 403-457. Wiley, New York. 

Bolin, B. (1970a). Changes of land biota and their importance for the carbon cycle. Science 196, 613-615. 

Calculated from carbon in ocean biota (3000 Tg) and approximate mass ratio for sulfur to carbon of 1 100. 

The BUSES model provides an estimate of the organic carbon/water partition coefficient (Koc) based on the octanol/water partition coefficient (Kow)- From these data, it is evident that the methyltins are less likely to partition onto organic carbon (in sediments, soils, biota) than are the butyl- and octyltin compormds due to then-lower partition coefficients and higher water solubilities. The 7/oc value can then be used to derive sohds/water partition coefficients in suspended matter, in sediment, and in soil using values of 10%, 5%, and 2% for organie carbon, representing typical organic carbon contents of suspended matter, sediment, and soil, respeetively. 

To solve this problem, we need to make computer calculations on the long-term global carbon cycle including the effect of terrestrial biota, ocean circulation pattern, and metamorphic activities which are not included in Kashiwagi et al. (2000) s computation. 

The evaluative lake environment is similar to the "unit world" described by Mackay and Paterson (2), consisting of a 1 km square area with an atmosphere 6000 m high, a water column 80 m deep (the approximate depth of Lake Michigan) containing suspended solids (5 parts per million by volume) and biota (considered to be fish) of 1 ppm by volume, and underlain by a sediment 3 cm deep. The bottom sediment contains 4% organic carbon and the value for suspended sediment was arbitrarily selected as ten times these bottom sediment values reflecting the enhanced sorption discussed by O Connor and Connally (14). 

DEHP has a branch-like structure with two side alkyl chains, each chain comprised of eight carbons. This molecular structure reflects DEHP s poor water solubility compared to PAEs containing shorter alkyl chain lengths. DEHP can readily accumulate in lipids of aqueous biota when present in water due to its high... 

For many hydrophilic compounds such as the alcohols, Kow is low and can be less than 1.0, resulting in negative values of log Kow. In such cases, care should be taken when using correlations developed for more hydrophobic chemicals since partitioning into biota or organic carbon phases may be primarily into aqueous rather than organic media. 

What is the role of marine biota and benthic-pelagic coupling in the carbon cycling and primary production ... 

Since the biospheric growth rate depends, among other factors, on the C02 supply, it is probable that the C02 increase induces, at least for part of the biosphere, an increased growth rate ("C02 fertilization"). A simple concept to take this into account is the introduction of a biota growth factor e if the atmospheric C02 pressure increases by p percent, the C02 flux to the biosphere increases by zp percent. Typically, values for e between 0 and 0.5 have been used in carbon cycles models [26,41]. 

While all the living matter in the oceans contains only about 3 billion tons of carbon, ten thousand times that amount is dissolved in the oceans, mostly in nonliving form. The carbonate sediments in the continental crust and the ocean floor contain almost 70 million billion tons of carbon. These are huge quantities compared to the atmosphere and living and dead biota. 

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