Dissolved organic matter in seawater

Seawater DOM has numerous sources and sinks and a range of potential reactions. Sources of the sub-micron components include exudation from phytoplankton, microbial degradation of bioparticles, animal wastes (excretion), viral infection of bacteria, sloppy feeding by zooplankton and other animals, and input of dissolved molecules from rivers and surface sediments. Removal mechanisms include photodegradation, sorption to sinking particles, and microbial utilization. Tritiated thymidine and leucine uptake experiments indicate that up to half of the carbon formed by photosynthesis is shunted via dissolved organic molecule intermediates into bacteria. 

Abbreviations C = C, percentage of unsaturated carbon (largely aromatic) LOPs, lignin oxidation products %BOC, percentage of total dissolved organic carbon that occurs in chromatographically measurable biochemicals. 

Sources Hedges et al. (1997) (and references therein) Benner et al. (1992) Opsahl and Benner (1997). 

Vertical profiles of concentration (circles) and A C (squares) versus water column depth for dissolved organic carbon in the temperate Pacific Ocean (after Druffel et a/., 1989). 

The bulk chemical composition of seawater DOM (Table 8.8), however, is not consistent with a predominant riverine origin. In particular, seawater DOM is depleted in C and enriched in C and compared with most DOM discharged by rivers (with the Amazon being taken here as an example). Seawater DOM is also depleted in aromatic carbon (as measured by C NMR) and lignin phenol structural units (as determined by CuO oxidation), possibly as a consequence both of the low phenol content of marine plankton, and of selective alteration of aromatic carbon by photodegradation. Thus all evidence to date, including elevated total concentrations in surface marine waters (Fig. 8.19), indicates that seawater DOM is largely 

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Essentially all the dissolved organic matter in seawater can be assumed to be non-living. However, particulate organic matter can be either living or dead, with the latter often referred to as "detritus."... 

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Repeta DJ, Hartman NT, John S, Jones AD, Goericke R (2004) Structure Elucidation and Characterization of Polychlorinated Biphenyl Carboxylic Acids as Major Constituents of Chromophoric Dissolved Organic Matter in Seawater. Environ Sci Tech 38 5373... 

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McCarthy, M. D., J. I. Hedges, and R. Benner. 1993. The chemical composition of dissolved organic matter in seawater. Chemical Geology 107 503-507. 

There is abundant evidence from culture studies that both AOB and NOB are photosensitive. It is a high priority to investigate the photosensitivity of AOA. Even if aU nitrifiers exhibit photoinhibiton in some form, however, the direct and indirect ecological imphcations of this physiology for the rates and distributions of nitrification in the environment are not easily predicted. Dissolved organic matter in seawater, as well as turbidity due to sediments or phytoplankton, might aU provide photoprotection in surface waters, and regulation of nitrification by other factors discussed in this section may be much more important in many environments. 

Boehm, P. D. and Quinn, J. G. (1973). Solubilization of hydrocarbons by the dissolved organic matter in seawater. Geochim. Cosmochim. Acta 37, 2459-2477. 

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Dissolved organic matter in seawater interferes with the voltanunetric antdysis as it reduces the sensitivity due to physical effects as a result of competitive adsorption on the... 

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Jiang, F., Lee, F.S., Wang, X., and Dai, D. (2008). The application of excitation/emission matrix spectroscopy combined with multivariate analysis for the characterization and source identification of dissolved organic matter in seawater of Bohai Sea, China. Mar. Chem., 110,109-119. 

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