Production of Organic Matter

Shallow zones of DOM and POM production are inherently linked with the cycling and exchange of the adjacent deep channel environments of estuaries (Malone et al., 1986 Kuo and Park, 1995). Recent models have now included shallow environments in the wider-scale predictive models of organic matter cycling of estuaries (Pinckney and Zingmark, 1993 Madden and Kemp, 1996 Buzzelli et al., 1998). 

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Hydrogen sulfide is a commonly occurring decomposition product of organic matter. It is relatively water soluble at higher pHs where it is predominantly dissociated as and S ions. As the pH is decreased below 7, undissociated gas HjS begins to predominate and is released. Since its vapor density is > 1.0, HjS gas tends to settle in low places and creates a toxicity hazard. H S is readily oxidizable by a number of means to less toxic SO3" or 804 forms. 

Growth can be defined as the production of organic matter by increase in size or volume. This process involves the uptake of water, carbon dioxide and minerals. In plants, growth is made possible by the process of photosynthesis, which produces the sugars (as primary components) from which compounds such as starch, cellulose, amino acids and proteins are derived. 

Here, we should notice that production of organic matters from carbon dioxide using hydrogenotrophs may play an important role in future [18],... 

Simple organic molecules such as small carboxylic acids (oxalate, acetate, malonate, citrate, etc.), amino acids and phenols are all ligands for metals. Such compounds may all occur as degradation products of organic matter in natural waters. The complexes formed are typically charged hydrophilic complexes. The stability of the metal complexes with these ligands is, however, moderate in most cases. Model calculations including such compounds at realistic concentrations indicate that their effects on speciation are relatively small [29],... 

Ambient concentrations of COj are very low and usually biolimiting. Hence phytoplankton generally rely on bicarbonate as their carbon source. Phytoplankton must convert this bicarbonate to COj to enable production of organic matter. This conversion is facilitated by the Zn-containing enzyme, carbonic anhydrase (Table 11.4). Some phytoplankton release carbonic anhydrase into seawater with the resulting COj then transported across their cell membrane. 

Moreover, both river induced up-welling and river discharge of nutrients create a fertile environment which enhances the primary production of organic matter in off-shore direction of estuaries. It can be predicted from these observations that heterogeneous reactions between dissolved and both mineral phase and biota will be predominant in estuaries and coastal zones. These reactions will primarily affect those elements and compounds which are located at the particulate surface. The determination of surface properties of particles appear to be an important key to understand the interactions of trace elements and organic compounds between particulate and dissolved phases in estuarine and coastal systems. 

Within interstitial habitats of sandy beaches, particles are trapped in the upper 5-cm surface layer and give rise to a bacterial-protozoan community.5 Below this level, a bacterial flora attached to sand grains removes some of the dissolved organic carbon while supporting a meiofauna community comprised of nematods and copepods. The biotic community of these intertidal sandflats is supplemented by the production of organic matter via benthic diatoms which migrate vertically with the tides. 

To estimate the productivity of marine ecosystems, two parameters are usually considered the rate of the production of organic matter by plant organisms per unit time (primary production) and the specific rate of the increase in the amount of the matter synthesized by organisms or groups of organisms per unit time. 

Brown, S., and A. E. Lugo. 1982. The storage and production of organic matter in tropical forests and their role in the global carbon cycle. Biotropica 4(3) 161-187. 

The major N product of organic matter decomposition in seawater is NH4+, but NH4+ is present at trace or undetectable levels in the huge volume of the deep ocean. Rather, deep water contains NOs" at 20-40 pM concentrations, which would seem to imply that nitrification occurs mainly in the deep ocean. Nitrate concentrations in the surface ocean are usually maintained at low levels because phytoplankton assimilate N03 more rapidly than it can be suppHed by mixing or diffusion from the deep NOs" reservoir. Ammonium, which is produced in the photic zone by heterotrophic processes, is also usually immediately assimilated by phytoplankton and heterotrophic bacteria before it can be nitrified. The important physical and biological differences in the source functions of NH4+ and NOs" are... 

Stigebrandt, A. (1991). Computations of oxygen fluxes through the sea surface and the net production of organic matter with application to the Baltic and adjacent seas. Limnol. Oceanogr. 36, 444—454. 

Dugdale, R. C. (1983). Effects of source nutrient concentrations and nutrient regeneration on production of organic matter in coastal upweUing centers. In Coastal UpweUing, Pt.A. (Suess, E., and Thiede, J., eds.). Plenum Press, New York. pp. 175-182. 

Duursma E. K. (1963) The production of dissolved organic matter in the sea, as related to the primary gross production of organic matter. Neth. J. Sea Res. 2, 85—94. 

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