Marine environment salinity

Yokoya et al. (1999) investigated growth and tolerance of G. vermiculophylla, taken from the marine environment (salinity varied between 29 and 34 psu), under a variation of temperature (5-30°C), salinity (5-60 psu), and photon irradiance (20-100 /imol photons m /s ). 

This removal may also include diffusion of soluble U(VI) from seawater into the sediment via pore water. Uranium-organic matter complexes are also prevalent in the marine environment. Organically bound uranium was found to make up to 20% of the dissolved U concentration in the open ocean." ° Uranium may also be enriched in estuarine colloids and in suspended organic matter within the surface ocean. " Scott" and Maeda and Windom" have suggested the possibility that humic acids can efficiently scavenge uranium in low salinity regions of some estuaries. Finally, sedimentary organic matter can also efficiently complex or adsorb uranium and other radionuclides. 

The characterisation of LAS degradation in the marine environment requires laboratory experiments, although due to the special characteristics of this compartment (e.g. its high salinity and its normally oligotrophic status) and the numerous variables that affect it, divergent results may be obtained. Marine-specific bacterial communities cannot be cultivated as a whole in standard media due to the difficulty of reproducing original ecosystem conditions where they have been... 

The presence of suspended solid materials increases the extent of LAS biodegradation [13,28], but the rate of the process remains invariable. The influence of the particulate material is due specifically to the increased density of the microbiota associated with sediments. However, suspended solids may also reduce the bioavailability of IAS as a result of its sorption onto preferential sites (e.g. clays, humic acids), although this is a secondary effect due to the reversibility of the sorption process. Salinity does not affect IAS degradation directly, but could also reduce LAS bioavailability by reducing the solubility of this molecule [5], Another relevant factor to be taken into account is that biodegradation processes in the marine environment could be limited by the concentration of nutrients, especially of phosphorus and nitrogen [34],... 

In summary, we can conclude that at moderate salt concentrations typical for seawater ( 0.5 M), salinity will affect aqueous solubility (or the aqueous activity coefficient) by a factor of between less than 1.5 (small and/or polar compounds) and about 3 (large, nonpolar compounds, n-alkanals). Hence, in marine environments for many compounds, salting-out will not be a major factor in determining their partitioning behavior. Note, however, that in environments exhibiting much higher salt concentrations [e.g., in the Dead Sea (5 M) or in subsurface brines near oil fields], because of the exponential relationship (Eq. 5-28), salting-out will be substantial (see also Illustrative Example 5.4). 

The apparent differences in identified photoproducts between marine and freshwater systems may be due to fundamental differences in DOM composition (see Chapters 3 and 5) or to differences in analytical approaches (e.g., capillary electrophoresis has often been the method of choice to identify DOM photoproducts in freshwater systems, but this method is not appropriate for high-salinity marine samples Table I). The fact that most of the labile photoproducts found only in freshwater environments have been identified by more than one analytical approach, however, suggests that methods alone cannot explain the 14 nonoverlapping photoproducts. On the other hand, studies conducted by the same researcher(s) tend to report the same suite of compounds, even across marine/freshwater boundaries (e.g., Kieber et al., 1990), suggesting that optimization of the analytical approach and/or researcher focus may be influencing the data. More studies identifying DOM photoproducts have been conducted in freshwater environments than in marine environments (12 vs. 6), a factor that is also likely to influence the number of reported photoproducts. At this point, evidence is insufficient to determine whether DOM photoproducts that are currently unique to either marine or freshwater environments can be attributed to inherent DOM compositional differences or to analytical approach. 

More recent work emphasizes the synthesis by the fish of polyunsaturated fatty acids in the marine environment. Borlongan and Benitez (1992) maintained groups of milkfish (which can tolerate salinities from 0 to 100%o) in fresh water or sea water on the same diet, and while the two groups showed no differences in their total lipid contents, the proportion of phospholipids in the lipids of various organs was the greater in fish from sea water. The organs of fish in fresh water contained lipids with higher proportions of neutral lipids. 

Plants with a different biochemistry are found in fresh water environments, as compared to marine environments. They decay to different products and the resultant peat will have a lower sulfur content. However, it is the fresh water contact that provides the general explanation of the low sulfur content of Western U.S. coals, and the saline water contact that provides the general explanation of the high sulfur content of the Eastern coals (Figure 1). Further evidence of this phenomenon is that those Eastern coal beds that have high sulfur content are overlain with marine shale or limestone, whereas the low sulfur coal beds are not (3, 14). 

Eremeev VN, Ivanov VA, Kosarev AN, Tuzhilkin VS (1994) Annual and semiannual harmonics in the climatic salinity field of the Black Sea. In Diagnosis of the state of marine environment of the Azov-Black Sea basin. MHI UAS, Sebastopol, p 89... 

The major constituents in seawater are conventionally taken to be those elements present in typical oceanic water of salinity 35 that have a concentration greater than 1 mg kg excluding Si, which is an important nutrient in the marine environment. The concentrations and main species of these elements are presented in Table 1. One of the most significant observations from the Challenger expedition of 1872-1876 was that these major components existed in constant relative amounts. As already explained, this feature was exploited for salinity determinations. Inter-element ratios are generally constant, and often expressed as a ratio to Cl%o as shown in Table 1. This implies conservative behaviour, with concentrations depending solely upon mixing processes, and indeed, salinity itself is a conservative index. 

Estuaries are the major pathway of materials from the rivers to the marine environment. In order to understand how dissolved and particulate organic matter v/ithin the estuary affect the speciation of cations within this environment, the ion exchange parameters as a function of ionic strength must be studied. In addition to the physical transfer of material between the dissolved and particulate forms, the salinity variations also affect the ion exchange abilities of these organic molecules. These two major processes can affect the organic material distribution and ability to bind metals, and hence the overall distribution of a given trace metal. 

The chemistry of the carbonic acid system in seawater has been one of the more intensely studied areas of carbonate geochemistry. This is because a very precise and detailed knowledge of this system is necessary to understand carbon dioxide cycling and the deposition of carbonate sediments in the marine environment. A major concept applicable to problems dealing with the behavior of carbonic acid and carbonate minerals in seawater is the idea of a constant ionic medium. This concept is based on the observation that the salt in seawater has almost constant composition, i.e., the ratios of the major ions are the same from place to place in the ocean (Marcet s principle). Possible exceptions can include seawater in evaporative lagoons, pores of marine sediments, and near river mouths. Consequently, the major ion composition of seawater can generally be determined from its salinity. It has been possible, therefore, to develop equations in which the influence of seawater composition on carbonate equilibria is described simply in terms of salinity. 

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