Oceans biological processes

Pos et ai, 1998). Colored dissolved organic material is frequently involved in such processes. Laboratory irradiation has confirmed that cysteine and cystine are efficient precursors of CS2 and that OH radicals are likely to be important intermediates (Xie et ai, 1998), but it is also likely that some of these sulfur gases are produced directly by biological processes. Ocean waters appear to be supersamrated in carbon disulfide and capable of yielding —0.1 Tg(S) yr (Xie and Moore, 1999). 

Almost all elements in the periodic table are involved in at least one way or another in the biological cycle of the ocean. Many elements are essential or required nutrients. Others are carried along as passive participants. In either case the rates of biological processes need to be known. 

Oceanic surface water is everywhere supersaturated with respect to the two solid calcium carbonate species calcite and aragonite. Nevertheless carbonate precipitation is exclusively controlled by biological processes, specifically... 

Carbon is released from the lithosphere by erosion and resides in the oceans ca. 10 years before being deposited again in some form of oceanic sediment. It remains in the lithosphere on the average 10 years before again being released by erosion (Broecker, 1973). The amount of carbon in the ocean-atmosphere-biosphere system is maintained in a steady state by geologic processes the role of biological processes is, however, of profound importance... 

Carbon dioxide plays a key role in climate, in biological processes, in weathering reactions, and in marine chemistry. I shall next describe how the partial pressure of this gas in the atmosphere may be calculated. Because there is a rapid exchange of carbon dioxide between ocean and atmosphere, we must consider the fate of dissolved carbon. 

The advent of new techniques to collect undisturbed sediment cores, with well preserved sediment - water interface has brought into sharper focus the various deep sea sedimentary processes, their rates and their effects on the preserved records. As mentioned earlier, recent studies have shown that the record contained in sediments is not a direct reflection of the delivery pattern of a substance to the ocean floor as has so far been assumed the record is modified as a result of several complex physical, chemical and biological processes. Therefore, information on the temporal variations in the tracer input to oceans, if sought, has to be deciphered from the sediment-residuum. In the following we consider one specific example of retrieval of information from the sediment pile the application of deep sea sediments to obtain historical records of cosmic ray intensity variations. 

Measures, C.I. and J.D. Burton. 1980. The vertical distribution and oxidation states of dissolved selenium in the northeast Atlantic ocean and their relationship to biological processes. Earth Plan. Sci. Lett. 46 385-396. Medeiros, L.C., R.P. Belden, and E.S. Williams. 1993. Selenium content of bison, elk and mule deer. Jour. 

This model was first applied to dissolved oxygen gas (O2) profiles to estimate the rate of aerobic respiration. This biological process is responsible fiar the presence of a pronounced mid-depth O2 concentration minimum in the mid- and low latitudes throughout all the ocean basins. The concentration minimum in the Atlantic can be seen in Figure 4.l4e. The solution to Eq. 4.14, in the presence of an upward vertical advection, is... 

Equation 8.4 predicts that aerobic respiration should release dissolved inorganic nitrogen and phosphorus into seawater in the same ratio that is present in plankton, i.e., 16 1. As shown in Figure 8.3, a plot of nitrate versus phosphate for seawater taken from all depths through all the ocean basins has a slope close to 16 1. Why do both plankton and seawater have an N-to-P ratio of 16 1 Does the ratio in seawater determine the ratio in the plankton or vice versa Current thinking is that the N-to-P ratio of seawater reflects a quasi steady state that has been established and stabilized by the collective impacts of several biological processes controlled by marine plankton. 

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